J Incl Phenom Macrocycl Chem DOI 10.1007/s10847-016-0687-z

ORIGINAL ARTICLE

Synthesis and crystal structures of p-tert-butyldihomooxacalix[4] arene mono-Schiff bases Yang Liu1 · Jing Sun1 · Chao-Guo Yan1 

Received: 11 September 2016 / Accepted: 10 December 2016 © Springer Science+Business Media Dordrecht 2017

Abstract The novel functionalized p-tert-butyldihomooxacalix[4]arene mono-Schiff bases were conveniently synthesized by sequential Gabriel amination reaction and condensation with substituted salicylaldehydes. The single crystal structures of p-tert-butyldihomooxacalix[4]arene mono-Schiff bases were determined by X-ray single crystal diffraction method. The coordination property of the representative mono-Schiff base to transition metal ions was also investigated by UV–vis spectroscopy.

Keywords Calixarene · Dihomooxacalix[4]arene · Schiff base · Crystal structure · UV–vis spectroscopy

Introduction As one of the most famous macrocycles, calixarenes are extensively exploited in supramolecular chemistry, nano-

Graphical Abstract

* Chao-Guo Yan [email protected] 1

School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China

material and various application fields because of their easy preparation, versatile chemical modification and diverse remarkable ability [1]. Consequently, other similar structural macrocycles such as thiacalixarenes, resorcinarenes, carlix pyrroles, and pillararenes have also attracted much attentions in supramolecular chemistry [2–4]. In this scenario, dihomooxacalix[4]arene, a calix[4]arene analogue in which one CH2 bridge is replaced by one CH2OCH2 group, nearly prepared at the same time and by the same procedure as calixarene, has remained largely less studied [5–9]. In recent years, the advantages of the p-tert-butyldihomooxacalix[4]arenes were gradually recognized by more

13

Vol.:(0123456789)

J Incl Phenom Macrocycl Chem

and more researchers [10–14]. Notably, dihomooxacalix[4]arenes have slightly larger cavity than that of calix[4] arenes. They usually possess a cone conformation but more flexible and the bridged oxygen atom might provide additional binding sites [15–21]. Marcos et al. prepared a couple of potential dihomooxacalix[4]arene receptors and systematically investigated their complexation properties for various cations and anions [22–30]. Again this background and in continuation of our work on the chemical modification and assembly study of calixarene and other macrocyclic compounds [31–34], herein we wish to describe the selective introduction of the functionalized mono-Schiff base on the lower rim of p-tert-butyldihomooxacalix[4] arene.

Results and discussion The synthetic process for the p-tert-butylhomooxacalix[4] arene mono-Schiff bases is  illustrated in Scheme  1. First, p-tert-butylhomooxacalix[4]arene reacted with slightly excess of N-chloroalkylphthalimide in refluxing acetone with potassium carbonate as the base and potassium

Scheme 1 Synthesis of p-tertbutyldihomooxacalix [4] arene mono-Schiff bases

13

iodide as catalyst for about 3  days. The desired monoalkylated products 2a–2c can be obtained in good yields. Using nearly equivalent amount of alkylating reagent and base, dihomooxacalix[4]arene can be selectively monoalkylated and the possible polyalkylated products were greatly decreased. After column chromatography, the pure alkylated products were easily obtained in good yields. Second, the reaction of compounds 2a–2c with the hydrated hydrazine in refluxing tetrahydrofuran resulted in the mono-aminoalkoxy substituted dihomooxacalix[4] arenes 3a–3c in satisfactory yields. Finally, the condensation reaction of dihomooxacalix[4]arenes 3a–3c with various substituted salicylaldehydes in ethanol afforded the desired dihomooxacalix[4]arenes 4a–4l in good yields. The structures of the prepared products were fully characterized by IR, HRMS, 1H and 13C NMR spectra. Because the mono-substituted dihomooxacalix[4]arenes are asymmetric molecules, the mono-Schiff bases 4a–4l usually reveal the relative complicate 1H and 13C NMR spectra. Some examples are: the 1H NMR spectrum of dihomooxacalix[4]arene 2a shows three singlets at 8.61, 8.26 and 7.74 ppm for the three phenolic hydroxyl groups. The five bridged methylene units and the ethylene units display several peaks at

J Incl Phenom Macrocycl Chem

Fig. 2 Molecular structure of compound 4c

Fig. 1 Molecular structure of compound 2c

4.86–3.24 ppm. The four tert-butyl groups show three singlets with a ratio of 2:1:1 at 1.22, 1.21, and 1.11  ppm. In the 1H NMR spectrum of mono-Schiff base 4b, the four phenolic hydroxy groups give four singlets at 13.32, 9.00, 8.38 and 7.51  ppm. The singlet at 8.74  ppm is belonging to the imino (CH=N) group and the three singlets at 1.23, 1.22 and 1.13 ppm are the absorptions of the four tert-butyl groups. Similarly, the couple of peaks at 4.97–3.27 ppm are the characteristic absorptions of the five bridged methylene units and one ethylene unit spacer. The single crystal structures of the dihomooxacalix[4] arene 2c, 4c, 4f and 4g were determined by X-ray diffraction method (Figs. 1, 2, 3, 4), which confirmed the elucidation of the molecular structures of the obtained compounds by the spectroscopic method. From Figs.  1, 2, 3 and 4, it is clearly seen that mono-alkylated substitution was located at one of the hydroxy groups of the two phenolic rings connected by the bridging methylene unit in the dihomooxacalix[4]arene. The dihomooxacalix[4]arene adopts a distorted cone-conformation, in which the two phenol rings connected by CH2OCH2 stretch much horizontal to the other phenol rings connected by CH2 unit. The Schiff base is located at lower rim of the dihomooxacalix[4]arene. In the molecular of compound 2c, the angles of the four phenolic rings to the perpendicular line are 43.652(112)°, 87.469(107)°, 48.400(119)°, 31.697(109)°, respectively. In the molecule, the substituted phenolic ring stands most perpendicularly than the other three unsubstituted phenolic rings. The similar structural patterns are also observed in other three dihomooxacalix[4]arene mono-Schiff bases. The corresponding angles of the four phenolic rings to the perpendicular line in compound 4c

Fig. 3 Molecular structure of compound 4f

Fig. 4 Molecular structure of compound 4g

are 32.307(57), 56.099(59)°, 66.300(52)°, 54.525(58)°, respectively. The coordination properties of one representative dihomooxacalix[4]arene mono-Schiff base to some transition

13

J Incl Phenom Macrocycl Chem

metal ions were investigated by UV–vis spectroscopy. The maximum absorption of the mono-Schiff base 4g appears at about 328 nm. Upon the addition of alkali and alkaline earth metal salts, nearly no changes of absorption were observed. This indicated that the mono-Schiff base 4g has negligible binding ability for these kinds of metal ions. When transition metal acetate salts (Cu2+, Co2+, Ni2+, Zn2+, Mn2+, Pd2+, Cd2+) were added, the maxim absorption obviously shifted to longer wavelength, which clearly indicated some coordination was formed between them. It is very interesting to find that very large shift of maxim absorption was observed for Cu2+ ion (381  nm) and ion Zn2+ (379  nm) (Fig.  5). Therefore, the titration of monoSchiff base 4g with different concentrations of Cu2+ ion (Fig. 6) and Zn2+ ion (Fig. 7) were determined in UV–vis spectra. From Figs. 6 and 7, the molar ratios of mono-Schiff bases 4g to Cu2+ ion and Zn2+ ion were determined as 2:1, which also indicates copper and zinc complex with 2:1 stoichiometry are formed. This preliminary coordination investigation clearly showed that the obtained dihomooxacalix[4]arene mono-Schiff bases are potential ligands for selective recognition for transition metal ions.

Conclusion In summary, we have successfully developed a convenient synthetic method for a series of p-tert-butyldihomooxacalix[4]arene mono-Schiff bases. The synthetic route included sequential alkylation with N-chloroalkylphthalimide, reaction with hydrated hydrazine and condensation with substituted salicylaldehydes. Furthermore, the molecular structures of the p-tert-butyldihomooxacalix[4]arene derivatives were clearly elucidated by the

−4

Fig. 5 UV–vis spectra of mono-Schiff base 4 g (5 × 10 mol/L) upon addition of various metal ions (1 × 10− 4mol/L)

13

Fig. 6 UV–vis spectra of mono-Schiff base 4  g [5 × 10− 4c(L)] with different concentrations of [c (Cu2+/c(L)]: 0, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0, 2.0, 5.0)

spectroscopic and X-ray diffraction methods. The coordination abilities of p-tert-butyldihomooxacalix[4]arene mono-Schiff bases towards transition metal ions were preliminarily investigated by UV–vis spectra. This study provided new examples for the chemical function and applications of the typical dihomooxacalix[4]arenes.

Experimental section General remarks All reagents and solvents were commercially available as analytical grade and used as received. Further purification and drying by standard method were employed and

Fig. 7 UV–vis spectra of mono-Schiff base 4  g [5 × 10− 4c(L)] with different concentrations of [c (Zn2+/c(L)]: 0, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0, 2.0, 5.0)

J Incl Phenom Macrocycl Chem

distilled prior to use when necessary. All evaporations of organic solvents were carried out with a rotary evaporator in conjunction with a water aspirator. p-tert-Butyldihomooxacalix[4]arene was prepared according to the published methods [10, 11]. Melting points were taken on a hot-plate microscope apparatus and were uncorrected. 1H and 13C NMR spectra were recorded with an Avance III400 MHz liquid-state NMR spectrophotometer. IR spectra were obtained on a Bruker Tensor27 spectrometer (KBr disc). HRMS were determined on Bruker maXis mass spectrometry. X-ray data were collected on a Bruker Smart APEX-2 diffractometer. Synthesis of 7,13,19,25-tetra-tert-butyl-28-(phthalimid oalkoxy)-27,29,30-trihydroxy-2,3-dihomo-3-oxacalix[4] arenes (2a–2c) A suspension of p-tert-butyldihomooxacalix[4]arene1 (5.9  mmol, 4.0  g) and anhydrous potassium carbonate (5.9  mmol, 0.82  g), potassium iodide (5.9  mmol, 0.98  g) in dry acetone (100  mL) was heated to refluxing under nitrogen for at least 0.5 h. Then, N-chloroalkylphthalimide (8.85 mmol) was added. The reaction mixture was refluxed for 3  days. After cooling to room temperature, the solid was filtrated out and solution was collected. After evaporation of the solvent, the oily residue was subjected to column chromatography with a mixture of light petroleum and ethyl acetate (V/V = 3:1) to give a yellowish product. Recrystallization from methanol gave a pure white solid 2a–2c (n = 2, 3, 4). Dihomooxacalix[4]arene 2a (n = 2): white solid, 45%, m.p.  128–130 °C; 1H NMR (400  MHz, CDCl3) δ 8.61 (s, 1H, OH), 8.26 (s, 1H, OH), 7.74 (s, 1H, OH), 7.74–7.72 (m, 2H, ArH), 7.68–7.66 (m, 2H, ArH), 7.29–7.27 (m, 2H, ArH), 7.19 (d, J = 2.4  Hz, 1H, ArH), 7.08–7.06 (m, 3H, ArH), 6.93 (d, J = 2.8  Hz, 1H, ArH), 6.78 (d, J = 2.4  Hz, 1H, ArH), 4.86 (d, J = 9.2  Hz, 1H, CH2), 4.41–4.38 (m, 3H, CH2), 4.29–4.24 (m, 3H, CH2), 4.21–4.17 (m, 1H, CH2), 4.13–4.04 (m, 3H, CH2), 3.52 (d, J = 13.6 Hz, 1H, CH2), 3.38 (d, J = 14.0 Hz, 1H, CH2), 3.24 (d, J = 13.2  Hz, 1H, CH2), 1.22 (s, 18H, C(CH3)3), 1.21 (s, 9H, C(CH3)3), 1.11 (s, 9H, C(CH3)3); 13C NMR (100 MHz, CDCl3) δ: 168.5, 150.6, 146.8, 144.3, 143.0, 134.2 (2C), 133.7 (2C), 131.8, 128.1, 127.8, 127.6, 127.5, 127.3, 127.0, 126.6, 125.9, 125.7, 125.5, 125.2, 124.8, 123.5 (2C), 123.4, 123.3, 121.8, 71.2, 50.8, 40.8, 40.0, 39.4, 34.1, 33.9, 31.8, 31.6, 31.5, 31.4, 31.1, 29.7; IR (KBr) υ: 3358, 2959, 2867, 1717, 1610, 1485, 1393, 1364, 1301, 1205, 1072, 1017, 969, 877, 815, 717 cm− 1; MS (m/z):HRMS (ESI) calcd. for C55H65NNaO7 ([M+Na]+): 874.4659, found: 874.4651. Dihomooxacalix[4]arene 2b (n = 3): white solid, 63%, m.p.  160–162 °C; 1H NMR (400  MHz, CDCl3) δ 9.10

(s, 1H, OH), 8.48 (s, 1H, OH), 7.88–7.86 (m, 2H, ArH), 7.74 (s, 1H, OH), 7.72–7.70 (m, 2H, ArH), 7.30–7.28 (m, 2H, ArH), 7.13 (d, J = 2.0  Hz, 1H, ArH), 7.09–7.07 (m, 2H, ArH), 7.03 (d, J = 1.6  Hz, 1H, ArH), 6.96 (d, J = 2.0 Hz, 1H, ArH), 6.87 (d, J = 2.0 Hz, 1H, ArH), 4.94 (d, J = 9.2 Hz, 1H, CH2), 4.70 (d, J = 10.0 Hz, 1H, CH2), 4.49–4.42 (m, 2H, CH2), 4.31 (d, J = 14.0 Hz, 1H, CH2), 4.25–3.97 (m, 6H, CH2), 3.55 (d, J = 13.6 Hz, 1H, CH2), 3.46 (d, J = 14.0 Hz, 1H, CH2), 3.32 (d, J = 13.2 Hz, 1H, CH2), 2.51 (brs, 2H, CH2), 1.27 (s, 9H, C(CH3)3), 1.23 (s, 18H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100 MHz, CDCl3) δ: 168.2, 152.7, 151.2, 149.3, 147.8, 147.7, 143.4, 142.3, 141.4, 133.9, 132.8, 132.1, 131.3, 128.4, 128.1, 127.4(2C), 126.7(2C), 126.5, 125.8, 125.6, 125.5, 125.1, 123.6, 123.3, 122.7, 122.6, 74.2, 72.2, 71.7, 35.1, 34.2, 33.9, 33.8, 32.8, 31.6, 31.5, 31.4, 31.1, 30.1, 29.4; IR (KBr) υ: 3380, 2959, 2869, 1715, 1608, 1486, 1394, 1366, 1298, 1202, 1121, 1077, 1003, 928, 877, 819, 789, 718  cm− 1; MS (m/z): HRMS (ESI) calcd. for C56H67NNaO7 ([M+Na]+): 888.4815, found: 888.4816. Dihomooxacalix[4]arene 2c (n = 4): white solid, 69%, m.p.  176–178 °C; 1H NMR (400  MHz, CDCl3) δ 9.17 (s, 1H, OH), 8.44 (s, 1H, OH), 7.85–7.83 (m, 2H, ArH), 7.73 (s, 1H, OH), 7.70–7.67 (m, 2H, ArH), 7.29 (s, 2H, ArH), 7.12 (d, J = 2.0  Hz, 1H, ArH), 7.09 (d, J = 2.4  Hz, 1H, ArH), 7.06 (d, J = 2.0  Hz, 1H, ArH), 7.03 (d, J = 2.4  Hz, 1H, ArH), 6.96 (d, J = 2.0  Hz, 1H, ArH), 6.88 (d, J = 2.4 Hz, 1H, ArH), 4.94 (d, J = 9.2 Hz, 1H, CH2), 4.70 (d, J = 10.0  Hz, 1H, CH2), 4.49–4.42 (m, 2H, CH2), 4.24 (d, J = 9.2  Hz, 1H, CH2), 4.19 (d, J = 13.6 Hz, 1H, CH2), 4.15–4.12 (m, 2H, CH2), 4.06 (d, J = 13.2 Hz, 1H, CH2), 3.89 (t, J = 6.0 Hz, 2H, CH2), 3.54 (d, J = 13.6 Hz, 1H, CH2), 3.42 (d, J = 14.0 Hz, 1H, CH2), 3.30 (d, J = 12.8 Hz, 1H, CH2), 2.13 (brs, 4H, CH2), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 9H, C(CH3)3), 1.23 (s, 9H, C(CH3)3), 1.12 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 168.5, 152.7, 151.2, 149.3, 147.8, 147.6, 143.5, 142.3, 141.4, 133.8, 132.8, 132.1, 131.3, 128.5, 128.1, 127.4, 127.3, 126.7, 126.6, 126.5, 125.8, 125.6, 125.4, 125.1, 123.6, 123.2, 122.7, 122.6, 75.8, 72.2, 71.7, 37.6, 34.2, 33.9, 33.8, 32.8, 31.6, 31.5, 31.4, 31.1, 30.0, 27.2, 25.3; IR (KBr) υ: 3382, 2958, 2869, 1714, 1608, 1486, 1395, 1365, 1298, 1204, 1120, 1077, 1044, 941, 876, 820, 789, 718 cm− 1; MS (m/z): HRMS (ESI) calcd. for C57H69NNaO7 ([M+Na]+):902.4972, found:902.4970. Synthesis of 7,13,19,25-tetra-tert-butyl-28-(aminoalkox y)-27,29,30-trihydroxy-2,3-dihomo-3-oxacalix[4]arenes (2a–2c) A mixture of dihomooxacalix[4]arene 2ª–2c (1.0  mmol) and hydrated hydrazine (4.0  mL, 80%) in 50 mL of tetrahedrofuran was refluxed for 24  h. Then, water was added

13

J Incl Phenom Macrocycl Chem

and the resulting solid was triturated with alcohol to give a yellow product. Recrystallization from ethanol gave a pure white solid of 3a–3c. Dihomooxacalix[4]arene 3a (n = 2): white solid, 91%, m.p.  148–150 °C;1H NMR (400  MHz, CDCl3) δ 7.30 (d, J = 2.4  Hz, 2H, ArH), 7.13–7.11 (m, 3H, ArH), 7.07 (d, J = 2.4 Hz, 1H, ArH), 6.97 (d, J = 2.8 Hz, 1H, ArH), 6.90 (d, J = 2.4 Hz, 1H, ArH), 4.94 (d, J = 9.2 Hz, 1H, CH2), 4.74 (d, J = 10.0 Hz, 1H, CH2), 4.56 (d, J = 12.8 Hz, 1H, CH2), 4.43 (d, J = 10.0  Hz, 1H, CH2), 4.28–4.21 (m, 3H, CH2), 4.16 (d, J = 13.6  Hz, 2H, CH2), 3.56 (d, J = 13.6  Hz, 1H, CH2), 3.46 (d, J = 13.6 Hz, 2H, CH2), 3.34 (d, J = 12.8 Hz, 2H, CH2), 1.26 (s, 9H, C(CH3)3), 1.24 (s, 9H, C(CH3)3), 1.23 (s, 9H, C(CH3)3), 1.15 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 152.5, 151.1, 150.6, 148.9, 147.9, 147.7, 146.8, 144.3, 143.7, 143.0, 142.5, 141.8, 132.7, 131.7, 128.4, 128.1, 127.8, 127.6, 127.5, 127.4, 127.0, 126.7(2C), 125.9, 125.5, 124.8, 122.7 (2C), 121.8, 71.2, 34.2, 34.0, 33.9, 33.8, 32.5, 31.8, 31.6, 31.5, 31.4(2C), 31.3, 31.2, 29.7; IR (KBr) υ: 3289, 2959, 2869, 1607, 1486, 1392, 1365, 1297, 1247, 1207, 1120, 1074, 975, 877, 814, 711  cm− 1; MS (m/z): HRMS (ESI) calcd. for C47H64NO5 ([M+H]+): 722.4784, found: 722.4801. Dihomooxacalix[4]arene 3b (n = 3): white solid, 94%, m.p.  156–158 °C; 1H NMR (600  MHz, CDCl3) δ 7.29 (d, J = 2.4 Hz, 2H, ArH), 7.13 (d, J = 2.4 Hz, 1H, ArH), 7.11 (d, J = 2.4  Hz, 1H, ArH), 7.08 (d, J = 1.8  Hz, 1H, ArH), 7.03 (d, J = 2.4  Hz, 1H, ArH), 6.96 (d, J = 1.8  Hz, 1H, ArH), 6.88 (d, J = 2.4  Hz, 1H, ArH), 4.94 (d, J = 9.6  Hz, 1H, CH2), 4.71 (d, J = 10.2  Hz, 1H, CH2), 4.48 (d, J = 12.6 Hz, 1H, CH2), 4.43 (d, J = 10.2 Hz, 1H, CH2), 4.28 (d, J = 13.8  Hz, 1H, CH2), 4.23 (d, J = 9.0  Hz, 1H, CH2), 4.20–4.18 (m, 2H, CH2), 4.09 (d, J = 13.2  Hz, 1H, CH2), 3.55 (d, J = 13.8  Hz, 1H, CH2), 3.45 (d, J = 13.8  Hz, 1H, CH2), 3.33 (d, J = 12.6  Hz, 1H, CH2), 3.22 (t, J = 6.0  Hz, 2H, CH2), 2.29 (brs, 1H, CH2), 2.14 (brs, 1H, CH2), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 152.6, 151.2, 149.3, 147.8, 147.7, 143.6, 142.5, 141.6, 132.7, 131.3, 128.4, 128.1, 127.4, 126.7, 126.6, 125.9, 125.7, 125.5, 125.1, 123.6, 122.7, 122.6, 75.1, 72.1, 71.6, 68.0, 39.5, 34.2, 33.9 (2C), 33.2, 32.7, 31.6, 31.5, 31.4, 31.3, 31.2, 30.1, 29.7, 25.6; IR (KBr) υ: 3381, 2959, 2868, 1604, 1485, 1390, 1364, 1298, 1205, 1120, 1075, 984, 920, 876, 820, 790  cm− 1; MS (m/z):HRMS (ESI) calcd. for C48H66NO5 ([M+H]+): 736.4941, found: 736.4955. Dihomooxacalix[4]arene 3c (n = 4): white solid, 94%, m.p.  168–170 °C;1H NMR (400  MHz, CDCl3) δ 7.30 (d, J = 2.4 Hz, 2H, ArH), 7.14 (d, J = 2.0 Hz, 1H, ArH), 7.10 (d, J = 2.0  Hz, 1H, ArH), 7.07 (d, J = 2.4  Hz, 1H, ArH), 7.03 (d, J = 2.0  Hz, 1H, ArH), 6.97 (d, J = 2.4  Hz, 1H, ArH), 6.89 (d, J = 2.4  Hz, 1H, ArH), 4.95 (d, J = 9.2  Hz, 1H, CH2), 4.71 (d, J = 10.0  Hz, 1H, CH2), 4.50 (d,

13

J = 12.8  Hz, 1H, CH2), 4.45 (d, J = 10.4  Hz, 1H, CH2), 4.29–4.24 (m, 2H, CH2), 4.12–4.07 (m, 3H, CH2), 3.55 (d, J = 13.6 Hz, 1H, CH2), 3.47 (d, J = 14.0 Hz, 1H, CH2), 3.30 (d, J = 12.8  Hz, 1H, CH2), 2.88 (t, J = 7.0  Hz, 2H, CH2), 1.98 (s, 4H, CH2), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ:152.7, 151.2, 149.4, 147.8, 147.6, 143.6, 142.9, 142.5, 141.5, 132.8, 131.3, 128.5, 128.1, 127.8, 127.5, 127.4, 126.7, 126.6(2C), 125.9, 125.8, 125.7, 125.5(2C), 125.1, 124.9, 123.6, 122.7, 122.6, 76.5, 72.2, 71.7, 71.3, 41.9, 34.2, 33.9 (3C), 32.8, 32.0, 31.6, 31.5, 31.4 (2C), 31.2, 30.0, 27.3; IR (KBr) υ: 3383, 2959, 2868, 1605, 1485, 1390, 1364, 1298, 1206, 1120, 1075, 980, 938, 877, 819, 793  cm− 1; MS (m/z): HRMS (ESI) calcd. for C49H68NO5 ([M+H]+): 750.5097, found: 750.5111. Synthesis of dihomooxacalix[4]arene Schiff bases A solution of dihomooxacalix[4]arene 3a–3c (0.7  mmol) and substituted salicylaldehyde (1.05  mmol) in 30mL of ethanol was refluxed overnight. The resulting precipitates were collected by filtration and washed with ethanol to give a light yellow solid, which was further subjected to column chromatography with a mixture of light petroleum and ethyl acetate (V/V = 8:1) as elute to give the product 4a–4l. Dihomooxacalix[4]arene 4a (n = 2, R=H): yellow solid, 42%, m.p. 150–152 °C; 1H NMR (400 MHz, CDCl3) δ 13.23 (brs, 1H, OH), 8.77 (s, 1H, CH=N), 7.54–7.52 (m, 1H, ArH), 7.29 (d, J = 2.4 Hz, 2H, ArH), 7.12–7.10 (m, 2H, ArH), 7.08 (d, J = 2.4  Hz, 1H, ArH), 7.07 (d, J = 2.4  Hz, 1H, ArH), 7.05 (d, t = 2.0 Hz, 1H, ArH), 6.97–6.95 (m, 1H, ArH), 6.90–6.87 (m, 2H, ArH), 6.83 (d, J = 2.4  Hz, 1H, ArH), 4.93 (d, J = 9.6  Hz, 1H, CH2), 4.86 (d, J = 9.2  Hz, 1H, CH2), 4.74 (d, J = 10.0  Hz, 1H, CH2), 4.53 (d, J = 12.8 Hz, 1H, CH2), 4.28–4.23 (m, 4H, CH2), 4.17–4.08 (m, 2H, CH2), 3.91 (d, J = 14.0  Hz, 1H, CH2), 3.53 (d, J = 13.6  Hz, 1H, CH2), 3.46 (d, J = 13.6  Hz, 1H, CH2), 3.30 (d, J = 14.0  Hz, 1H, CH2), 1.26 (s, 9H, C(CH3)3), 1.24 (s, 9H, C(CH3)3), 1.23 (s, 9H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ:168.7, 161.1, 152.6, 151.2, 148.8, 147.9, 147.7, 146.8, 144.3, 143.4, 142.5, 141.3, 132.7, 132.2, 131.5, 128.1, 128.0, 127.8, 127.5, 127.4, 127.0, 126.7, 126.5, 125.8, 125.7, 125.5(2C), 125.3, 125.2, 123.7, 122.7, 122.3, 118.4, 116.7, 74.8, 71.9, 71.5, 71.2, 59.5, 34.2(2C), 33.9 (2C), 33.8, 31.6, 31.5(2C), 31.4(2C), 31.2, 31.1, 29.7; IR (KBr) υ: 3372, 2959, 2868, 1633, 1486, 1391, 1365, 1283, 1206, 1120, 1075, 972, 931, 877, 816, 785, 756, 711  cm− 1; MS (m/z): HRMS (ESI) calcd. for C54H68NO6 ([M+H]+): 826.5047, found: 826.5039. Dihomooxacalix[4]arene 4b (n = 2, R=Cl): yellow solid, 56%, m.p. 154–156 °C; 1H NMR (400 MHz, CDCl3) δ 13.32 (brs, 1H, OH), 9.00 (s, 1H, OH), 8.74 (s, 1H,

J Incl Phenom Macrocycl Chem

CH=N), 8.38 (s, 1H, OH), 7.58 (d, J = 2.4  Hz, 1H, ArH), 7.51 (s, 1H, OH), 7.28 (d, J = 2.4  Hz, 1H, ArH), 7.22 (d, J = 2.4 Hz, 1H, ArH), 7.21–7.18 (m, 1H, ArH), 7.10–7.08 (m, 3  H, ArH), 7.03 (d, J = 2.4  Hz, 1H, ArH), 6.96 (d, J = 2.4  Hz, 1H, ArH), 6.82–6.80 (m, 2H, ArH), 4.97 (d, J = 9.2  Hz, 1H, CH2), 4.46–4.41 (m, 2H, CH2), 4.38–4.31 (m, 4H, CH2), 4.24 (d, J = 9.6  Hz, 2H, CH2), 4.12–4.05 (m, 2H, CH2), 3.55 (d, J = 13.6  Hz, 1H, CH2), 3.41 (d, J = 14.0  Hz, 1H, CH2), 3.27 (d, J = 12.8  Hz, 1H, CH2), 1.23 (s, 18H, C(CH3)3), 1.22 (s, 9H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 168.0, 162.5, 152.6, 151.1, 148.6, 148.1, 147.6, 143.6, 142.6, 141.2, 132.7, 131.9, 131.5, 131.4, 128.0, 127.8, 127.4, 127.3, 126.8, 126.6, 126.4, 125.8, 125.6, 125.4, 125.2, 123.6, 122.9, 122.2, 118.3, 74.4, 71.9, 71.5, 58.9, 34.2, 33.8 (3C), 32.5, 31.6, 31.5, 31.4 (2C), 31.2, 31.1, 30.1, 30.0; IR (KBr) υ: 3374, 2959, 2869, 1637, 1579, 1484, 1389, 1364, 1280, 1202, 1119, 1074, 1016, 971, 929, 877, 818, 787 cm− 1; MS (m/z): HRMS (ESI) calcd. for C54H67ClNO6 ([M+H]+): 860.4657, found: 860.4657. Dihomooxacalix[4]arene 4c (n = 2, R=Br): yellow solid, 54%, m.p.  148–150 °C; 1H NMR (400  MHz, CDCl3) δ 13.35 (brs, 1H, OH), 9.00 (s, 1H, OH), 8.73 (s, 1H, CH=N), 8.38 (s, 1H, OH), 7.71 (d, J = 2.4  Hz, 1H, ArH), 7.51 (s, 1H, OH), 7.34–7.32 (m, 1H, ArH), 7.28 (d, J = 2.4  Hz, 1H, ArH), 7.22 (d, J = 2.4  Hz, 1H, ArH), 7.10–7.08 (m, 3  H, ArH), 7.03 (d, J = 2.4  Hz, 1H, ArH), 6.97 (d, J = 2.4  Hz, 1H, ArH), 6.81 (d, J = 2.4  Hz, 1H, ArH), 6.77 (d, J = 8.8  Hz, 1H, ArH), 5.01 (d, J = 9.2  Hz, 1H, CH2), 4.48–4.41 (m, 2H, CH2), 4.38–4.30 (m, 4H, CH2), 4.24 (d, J = 9.6  Hz, 2H, CH2), 4.08 (t, J = 14.2  Hz, 2H, CH2), 3.55 (d, J = 13.6  Hz, 1H, CH2), 3.42 (d, J = 14.0  Hz, 1H, CH2), 3.27 (d, J = 12.8  Hz, 1H, CH2), 1.23 (s, 18H, C(CH3)3), 1.22 (s, 9H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 167.9, 152.6, 151.1, 148.6, 148.1, 147.6, 143.6, 142.6, 141.3, 134.7, 134.4, 132.7, 131.5, 128.0, 127.9, 127.4, 127.3, 126.8, 126.6, 126.4, 125.8, 125.6, 125.4, 125.2, 123.7, 122.9, 122.3, 118.8, 109.8, 74.4, 71.9, 71.6, 58.9, 34.2, 33.9, 33.8 (2C), 32.5, 31.6, 31.5, 31.4, 31.2, 31.1, 30.1; IR (KBr) υ: 3372, 2959, 2869, 1636, 1573, 1483, 1389, 1364, 1279, 1202, 1120, 1075, 1045, 972, 927, 877, 818, 788 cm− 1; MS (m/z): HRMS (ESI) calcd. for C54H67BrNO6 ([M+H]+): 904.4152, found: 904.4148. Dihomooxacalix[4]arene 4d (n = 2, R = 3,5-di(tertBu)): yellow solid, 46%, m.p.  156–158 °C; 1H NMR (400  MHz, CDCl3) δ 13.73 (brs, 1H, OH), 8.72 (s, 1H, OH), 8.71 (s, 1H, CH=N), 7.68 (s, 1H, OH), 7.51 (s, 1H, OH), 7.34–7.32 (m, 2H, ArH), 7.27 (d, J = 2.4  Hz, 1H, ArH), 7.23–7.22 (m, 2H, ArH), 7.02 (m, J = 2.4  Hz, 3  H, ArH), 6.92 (d, J = 2.4  Hz, 1H, ArH), 6.85 (d, J = 2.4  Hz, 1H, ArH), 4.87 (d, J = 9.2  Hz, 1H, CH2), 4.38 (d, J = 10.0  Hz, 2H, CH2), 4.23–4.16 (m, 4H, CH2), 4.09 (d,

J = 12.8 Hz, 2H, CH2), 3.79 (d, J = 14.0 Hz, 1H, CH2), 3.50 (d, J = 14.0 Hz, 1H, CH2), 3.33 (d, J = 12.4 Hz, 2H, CH2), 3.21 (d, J = 14.0 Hz, 1H, CH2), 1.43 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.21 (s, 9H, C(CH3)3), 1.15 (s, 9H, C(CH3)3), 1.12 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ:169.2, 158.0, 152.7, 151.1, 149.0, 147.8, 147.7, 143.1, 142.2, 141.3, 139.8, 136.5, 132.7, 131.4, 128.3, 128.1, 127.5, 127.4, 127.0, 126.7, 126.4, 126.2, 126.1, 125.6, 125.5, 125.3, 125.2, 123.6, 122.6, 122.5, 118.1, 75.3, 72.1, 71.7, 59.5, 34.8, 34.2(2C), 34.1, 33.8(3C), 32.6, 31.6 (2C), 31.5 (2C), 31.4 (2C), 31.2 (2C), 31.1, 30.1, 29.4 (2C), 29.2; IR (KBr) υ: 3385, 2959, 2870, 1634, 1484, 1391, 1364, 1299, 1247, 1204, 1119, 1075, 1047, 1020, 972, 927, 878, 819, 769  cm− 1; MS (m/z): HRMS (ESI) calcd. for C62H84NO6 ([M+H]+): 938.6299, found: 938.6308. Dihomooxacalix[4]arene 4e (n = 3, R=H): yellow solid, 41%, m.p.  138–140 °C; 1H NMR (400  MHz, CDCl3) δ 13.40 (brs, 1H, OH), 9.31 (s, 1H, OH), 8.66 (s, 1H, CH=N), 8.58 (s, 1H, OH), 7.81 (s, 1H, OH), 7.31 (d, J = 2.4 Hz, 1H, ArH), 7.28 (d, J = 8.0 Hz, 1H, ArH), 7.24 (d, J = 2.4  Hz, 1H, ArH), 7.15 (d, J = 2.4  Hz, 1H, ArH), 7.11–7.07 (m, 3H, ArH), 7.01–6.98 (m, 3H, ArH), 6.90 (d, J = 2.4  Hz, 1H, ArH), 6.77 (t, J = 7.2  Hz, 1H, ArH), 4.98 (d, J = 9.6  Hz, 1H, CH2), 4.73 (d, J = 10.0  Hz, 1H, CH2), 4.48 (d, J = 10.4  Hz, 1H, CH2), 4.40 (d, J = 12.8  Hz, 1H, CH2), 4.30–4.26 (m, 2H, CH2), 4.20–4.17 (m, 4H, CH2), 4.06 (d, J = 13.6  Hz, 1H, CH2), 3.56 (d, J = 13.6  Hz, 1H, CH2), 3.49 (d, J = 14.0 Hz, 1H, CH2), 3.24 (d, J = 12.8 Hz, 1H, CH2), 2.49 (brs, 2H, CH2), 1.26 (s, 9H, C(CH3)3), 1.24 (s, 9H, C(CH3)3), 1.24 (s, 9H, C(CH3)3), 1.12 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ:166.6, 164.7, 161.1, 159.8, 152.6, 151.1, 149.1, 147.8, 147.7, 143.7, 142.5, 141.6, 133.4, 132.7, 132.5, 132.1, 131.4, 131.2, 128.3, 128.1, 127.5, 127.4, 126.7, 126.6, 126.5, 125.9, 125.8, 125.6, 125.1, 123.6, 122.8, 122.5, 119.7, 118.8, 118.5, 117.2, 117.1, 116.8, 73.3, 72.2, 71.6, 55.7, 34.2, 33.9, 33.8, 32.8, 31.6, 31.5, 31.4 (2C), 31.2, 31.1, 30.0; IR (KBr) υ: 3379, 2959, 2869, 1632, 1487, 1365, 1281, 1204, 1119, 1075, 982, 935, 876, 818, 788, 756 cm− 1; MS (m/z): HRMS (ESI) calcd. for C55H70NO6 ([M+H]+): 840.5203, found: 840.5207. Dihomooxacalix[4]arene 4f (n = 3, R=Cl): yellow solid, 54%, m.p. 164–166 °C; 1H NMR (400 MHz, CDCl3) δ 9.28 (s, 1H, OH), 8.64 (s, 1H, CH=N), 8.55 (s, 1H, OH), 7.82 (s, 1H, OH), 7.31 (d, J = 2.4  Hz, 1H, ArH), 7.24 (d, J = 2.4  Hz, 1H, ArH), 7.21–7.18 (m, 1H, ArH), 7.16 (d, J = 2.4 Hz, 1H, ArH), 7.11 (d, J = 2.4 Hz, 1H, ArH), 7.08 (d, J = 2.4  Hz, 1H, ArH), 7.04 (d, J = 2.8  Hz, 1H, ArH), 7.01–6.98 (m, 2H, ArH), 6.91–6.88 (m, 2H, ArH), 4.99 (d, J = 9.6 Hz, 1H, CH2), 4.74 (d, J = 10.0 Hz, 1H, CH2), 4.49 (d, J = 10.0 Hz, 1H, CH2), 4.35 (d, J = 12.8 Hz, 1H, CH2), 4.30–4.26 (m, 2H, CH2), 4.21–4.16 (m, 4H, CH2), 4.05 (d, J = 13.6 Hz, 1H, CH2), 3.57 (d, J = 13.6 Hz, 1H, CH2), 3.49

13

J Incl Phenom Macrocycl Chem

(d, J = 14.0 Hz, 1H, CH2), 3.21 (d, J = 12.8 Hz, 1H, CH2), 2.49 (brs, 2H, CH2), 1.26 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.12 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 166.0, 159.8, 152.4, 151.1, 149.0, 147.8, 147.7, 143.8, 142.6, 141.7, 136.9, 132.7, 132.0, 131.2, 130.6, 128.2, 127.4(2C), 126.8, 126.6, 126.5, 125.9, 125.8, 125.6, 125.1, 123.7, 123.1, 122.8, 122.5, 119.5, 118.4, 73.0, 72.2, 71.6, 55.6, 36.4, 34.2, 33.9, 33.8, 32.8, 31.6, 31.5, 31.4(2C), 31.1, 31.0, 30.0, 29.7; IR (KBr) υ: 3374, 2959, 2869, 1635, 1485, 1365, 1280, 1204, 1119, 1076, 979, 938, 877, 819, 789 cm− 1;MS (m/z): HRMS (ESI) calcd. for C55H69ClNO6 ([M+H]+): 874.4813, found: 874.4809. Dihomooxacalix[4]arene 4g (n = 3, R=Br): yellow solid, 51%, m.p. 136–138 °C; 1H NMR (400 MHz, CDCl3) δ 9.28 (s, 1H, OH), 8.64 (s, 1H, CH=N), 8.55 (s, 1H, OH), 7.81 (s, 1H, OH), 7.34–7.31 (m, 2H, ArH), 7.24 (d, J = 2.0 Hz, 1H, ArH), 7.20 (d, J = 2.4 Hz, 1H, ArH), 7.16 (d, J = 2.4  Hz, 1H, ArH), 7.11 (d, J = 2.4  Hz, 1H, ArH), 7.08 (d, J = 2.4  Hz, 1H, ArH), 7.01–6.98 (m, 2H, ArH), 6.90 (d, J = 2.4  Hz, 1H, ArH), 6.84 (d, J = 8.8  Hz, 1H, ArH), 4.99 (d, J = 9.6 Hz, 1H, CH2), 4.75 (d, J = 10.0 Hz, 1H, CH2), 4.49 (d, J = 10.4  Hz, 1H, CH2), 4.35 (d, J = 12.8 Hz, 1H, CH2), 4.30–4.26 (m, 2H, CH2), 4.20–4.14 (m, 4H, CH2), 4.04 (d, J = 13.6  Hz, 1H, CH2), 3.56 (d, J = 13.6 Hz, 1H, CH2), 3.49 (d, J = 14.0 Hz, 1H, CH2), 3.21 (d, J = 12.8 Hz, 1H, CH2), 2.49 (brs, 2H, CH2), 1.26 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.12 (s, 9H, C(CH3)3); 13 C NMR (100 MHz, CDCl3) δ: 165.9, 160.3, 154.5, 152.4, 151.1, 149.1, 147.8, 147.7, 143.7, 142.6, 141.7, 134.8, 133.6, 132.7, 131.2, 128.2, 127.4 (2C), 126.8, 126.6, 126.5, 125.9, 125.8, 125.6, 125.1, 123.7, 122.8, 122.5, 120.1, 118.8, 109.9, 73.0, 72.2, 71.6, 55.6, 34.2, 33.9, 33.8, 32.8, 31.6, 31.5, 31.4, 31.3, 31.1, 31.0, 30.0, 29.7; IR (KBr) υ: 3375, 2959, 2869, 1634, 1607, 1573, 1484, 1365, 1280, 1204, 1119, 1075, 979, 937, 877, 819, 789  cm− 1; MS (m/z):HRMS (ESI) calcd. for C55H69BrNO6 ([M+H]+): 918.4308, found: 918.4303. Dihomooxacalix[4]arene 4h (n = 3, R = 3,5-di(t-Bu)): yellow solid, 47%, m.p. 148–150 °C; 1H NMR (400 MHz, CDCl3) δ 9.35 (s, 1H, OH), 8.80 (s, 1H, CH=N), 8.57 (s, 1H, OH), 7.80 (s, 1H, OH), 7.35 (d, J = 2.8 Hz, 1H, ArH), 7.31 (d, J = 2.0  Hz, 1H, ArH), 7.24 (d, J = 2.0  Hz, 1H, ArH), 7.15 (d, J = 2.0  Hz, 1H, ArH), 7.11 (d, J = 2.0  Hz, 1H, ArH), 7.08 (d, J = 1.6  Hz, 1H, ArH), 7.02 (d, J = 2.0 Hz, 1H, ArH), 6.98 (d, J = 2.0 Hz, 2H, ArH), 6.89 (d, J = 2.0  Hz, 1H, ArH), 4.99 (d, J = 9.2  Hz, 1H, CH2), 4.75 (d, J = 10.0  Hz, 1H, CH2), 4.49–4.41 (m, 2H, CH2), 4.31–4.12 (m, 6 H, CH2), 4.06 (d, J = 13.6 Hz, 1H, CH2), 3.56 (d, J = 13.6  Hz, 1H, CH2), 3.49 (d, J = 14.0  Hz, 1H, CH2), 3.24 (d, J = 12.8 Hz, 1H, CH2), 2.50 (brs, 2H, CH2), 1.44 (s, 9H, C(CH3)3), 1.25 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.15 (s, 9H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13 C NMR (100 MHz, CDCl3) δ: 168.1, 158.1, 152.5, 151.2,

13

149.2, 147.7, 143.6, 142.5, 141.6, 139.9, 136.4, 132.8, 131.3, 128.4, 128.1, 127.5, 127.4, 126.8, 126.7, 126.6, 126.5, 126.0, 125.9, 125.8, 125.5, 125.1, 123.7, 122.7 (2C), 117.9, 73.1, 72.2, 71.6, 55.3, 35.0, 34.2, 33.9 (2C), 33.8 (2C), 32.9, 31.6, 31.5, 31.4(2C), 31.1, 31.0, 29.9, 29.4, 29.3; IR (KBr) υ: 3384, 2959, 2869, 1632, 1485, 1388, 1364, 1296, 1248, 1205, 1119, 1075, 981, 934, 877, 822, 768  cm− 1; MS (m/z): HRMS (ESI) calcd. for C63H86NO6 ([M+H]+): 952.6455, found: 952.6453. Dihomooxacalix[4]arene 4i (n = 4, R=H): yellow solid, 47%, m.p. 136–138 °C; 1H NMR (400 MHz, CDCl3) δ 9.25 (s, 1H, OH), 8.50 (s, 1H, OH), 8.46 (s, 1H, CH=N), 7.77 (s, 1H, OH), 7.31–7.27 (m, 3H, ArH), 7.14–7.10 (m, 3H, ArH), 7.07–7.03 (m, 2H, ArH), 6.96–6.92 (m, 2H, ArH), 6.89–6.83 (m, 2H, ArH), 4.94 (d, J = 9.6  Hz, 1H, CH2), 4.70 (d, J = 10.4  Hz, 1H, CH2), 4.52–4.44 (m, 2H, CH2), 4.27–4.24 (m, 2H, CH2), 4.14 (t, J = 5.4  Hz, 2H, CH2), 4.07 (d, J = 13.6  Hz, 1H, CH2), 3.89–3.81 (m, 2H, CH2), 3.55 (d, J = 13.6  Hz, 1H, CH2), 3.45 (d, J = 13.6  Hz, 1H, CH2), 3.30 (d, J = 12.8 Hz, 1H, CH2), 2.19 (brs, 4H, CH2), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ:165.2, 161.3, 152.7, 151.2, 150.1, 149.3, 147.8, 143.5, 142.4, 141.5, 132.7, 132.1, 131.2, 128.4, 128.1, 127.4(2C), 126.7, 126.6, 126.5, 126.1, 125.9, 125.7, 125.5, 125.1, 123.6, 122.7, 122.6, 118.4, 117.0, 76.3, 74.1, 72.2, 71.6, 59.1, 34.2, 33.9, 33.8, 31.6, 31.5, 31.4 (2C), 31.3, 31.1, 30.0, 27.6 (2C); IR (KBr) υ: 3380, 2958, 2869, 1632, 1486, 1365, 1284, 1205, 1119, 1076, 978, 942, 877, 818, 785, 757 cm− 1; MS (m/z): HRMS (ESI) calcd. for C56H72NO6 ([M+H]+): 854.5360, found: 854.5358. Dihomooxacalix[4]arene 4j (n = 4, R=Cl): yellow solid, 64%, m.p. 206–208 °C; 1H NMR (400 MHz, CDCl3) δ 9.24 (s, 1H, OH), 8.49 (s, 1H, OH), 8.40 (s, 1H, CH=N), 7.78 (s, 1H, OH), 7.30 (d, J = 2.4 Hz, 2H, ArH), 7.24–7.21 (m, 1H, ArH), 7.18 (d, J = 2.4  Hz, 1H, ArH), 7.14 (d, J = 2.4 Hz, 1H, ArH), 7.10 (d, J = 2.4 Hz, 1H, ArH), 7.08 (d, J = 2.4  Hz, 1H, ArH), 7.03 (d, J = 2.4  Hz, 1H, ArH), 6.97 (d, J = 2.4  Hz, 1H, ArH), 6.90–6.88 (m, 2H, ArH), 4.93 (d, J = 9.2  Hz, 1H, CH2), 4.68 (d, J = 10.0  Hz, 1H, CH2), 4.51–4.44 (m, 2H, CH2), 4.26–4.22 (m, 2H, CH2), 4.16–4.13 (m, 2H, CH2), 4.06 (d, J = 13.2  Hz, 1H, CH2), 3.92–3.81 (m, 2H, CH2), 3.55 (d, J = 13.6  Hz, 1H, CH2), 3.45 (d, J = 14.0  Hz, 1H, CH2), 3.31 (d, J = 12.8  Hz, 1H, CH2), 2.18 (brs, 4H, CH2), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 164.2, 160.0, 152.6, 151.1, 149.2, 147.7(2C), 143.6, 142.5, 141.5, 132.7, 131.9, 131.2, 130.4, 128.4, 128.1, 127.4, 126.7, 126.6, 126.4, 125.9, 125.7, 125.5, 125.1, 123.6, 122.7, 122.6, 118.6, 76.1, 72.1, 71.6, 59.0, 34.2, 33.9, 33.8(2C), 32.8, 31.6, 31.5, 31.4, 31.3, 31.1, 30.0, 27.6, 27.5; IR (KBr) υ: 3372, 2958, 2870, 1635, 1485, 1364, 1283, 1203, 1118, 1076, 1006, 980, 942, 916,

J Incl Phenom Macrocycl Chem

878, 819, 786, 763  cm− 1; MS (m/z): HRMS (ESI) calcd. for C56H71ClNO6 ([M+H]+): 888.4970, found: 888.4965. Dihomooxacalix[4]arene 4k (n = 4, R=Br): yellow solid, 59%, m.p. 146–148 °C; 1H NMR (400 MHz, CDCl3) δ 9.24 (brs, 1H, OH), 8.53 (brs, 1H, OH), 8.40 (s, 1H, CH=N), 7.78 (brs, 1H, OH), 7.36–7.33 (m, 1H, ArH), 7.32 (d, J = 2.4  Hz, 1H, ArH), 7.30 (d, J = 2.0  Hz, 2H, ArH), 7.14 (d, J = 2.0  Hz, 1H, ArH), 7.10 (d, J = 2.4  Hz, 1H, ArH), 7.08 (d, J = 2.4  Hz, 1H, ArH), 7.03 (d, J = 2.4 Hz, 1H, ArH), 6.97 (d, J = 2.4 Hz, 1H, ArH), 6.89 (d, J = 2.4  Hz, 1H, ArH), 6.84 (d, J = 8.8  Hz, 1H, ArH), 4.93 (d, J = 9.2  Hz, 1H, CH2), 4.68 (d, J = 10.0  Hz, 1H, CH2), 4.51–4.44 (m, 2H, CH2), 4.26–4.22 (m, 2H, CH2), 4.15–4.13 (m, 2H, CH2), 4.06 (d, J = 13.6  Hz, 1H, CH2), 3.93–3.81 (m, 2H, CH2), 3.55 (d, J = 13.6  Hz, 1H, CH2), 3.45 (d, J = 14.0  Hz, 1H, CH2), 3.31 (d, J = 12.8  Hz, 1H, CH2), 2.17 (brs, 4H, CH2), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 17H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 164.1, 160.5, 152.6, 151.1, 149.2, 147.7 (2C), 143.6, 142.5, 141.5, 134.7, 133.4, 132.7, 131.2, 128.4, 128.1, 127.4, 126.7, 126.6, 126.4, 125.9, 125.7, 125.5, 125.1, 123.6, 122.7, 122.6, 119.1, 110.0, 109.8, 76.1, 72.1, 71.6, 59.0, 34.2, 33.9, 33.8(2C), 32.8, 31.6, 31.5, 31.4, 31.3, 31.1, 30.0, 27.6, 27.5; IR (KBr) υ: 3380, 2958, 2869, 1635, 1484, 1364, 1282, 1203, 1120, 1076, 978, 943, 876, 819, 787  cm− 1; MS (m/z): HRMS (ESI) calcd. for C56H71BrNO6 ([M+H]+): 932.4465, found: 932.4451. Dihomooxacalix[4]arene 4l (n = 4, R = 3,5-di(t-Bu)): yellow solid, 51%, m.p. 148–150 °C; 1H NMR (400 MHz, CDCl3) δ 9.27 (s, 1H, OH), 8.52 (s, 1H, OH), 8.46 (s, 1H, CH=N), 7.78 (s, 1H, OH), 7.36 (d, J = 2.4  Hz, 1H, ArH), 7.29 (d, J = 2.0  Hz, 2H, ArH), 7.13 (d, J = 2.0  Hz, 1H, ArH), 7.10 (d, J = 2.4 Hz, 1H, ArH), 7.07 (t, J = 2.2 Hz, 2H, ArH), 7.03 (d, J = 2.4 Hz, 1H, ArH), 6.96 (d, J = 2.4 Hz, 1H, ArH), 6.88 (d, J = 2.4  Hz, 1H, ArH), 4.94 (d, J = 9.6  Hz, 1H, CH2), 4.70 (d, J = 10.0  Hz, 1H, CH2), 4.53–4.44 (m, 2H, CH2), 4.26–4.23 (m, 2H, CH2), 4.16–4.13 (m, 2H, CH2), 4.08 (d, J = 13.6  Hz, 1H, CH2), 3.87–3.78 (m, 2H, CH2), 3.55 (d, J = 13.6 Hz, 1H, CH2), 3.44 (d, J = 14.0 Hz, 1H, CH2), 3.31 (d, J = 12.8  Hz, 1H, CH2), 2.17 (brs, 4H, CH2), 1.43 (s, 9H, C(CH3)3), 1.28 (s, 9H, C(CH3)3), 1.27 (s, 9H, C(CH3)3), 1.24 (s, 18H, C(CH3)3), 1.13 (s, 9H, C(CH3)3); 13C NMR (100  MHz, CDCl3) δ: 166.3, 158.2, 152.7, 151.2, 150.6, 149.4, 147.8, 147.6, 146.8, 144.3, 143.5, 142.4, 141.4, 139.8, 136.6, 132.8, 131.2, 128.5, 128.1, 127.8, 127.5, 127.4, 127.0, 126.7, 126.6, 126.5, 125.9, 125.8, 125.7, 125.5 (2C), 125.1, 124.7, 123.6, 122.7, 122.6, 121.8, 117.9, 76.4, 72.2, 71.7, 71.2, 59.1, 35.0, 34.2, 34.1, 34.0, 33.9, 33.8, 32.8, 31.8, 31.6, 31.5(2C), 31.4 (2C), 31.3, 31.1, 30.0, 29.4, 29.3, 27.7, 27.6; IR (KBr) υ: 3384, 2959, 2869, 1634, 1485, 1389, 1364, 1296, 1248, 1205, 1120, 1076, 983, 940, 877, 817, 767, 709 cm− 1; MS (m/z):

HRMS (ESI) calcd. for C64H88NO6 ([M+H]+): 966.6612, found: 966.6596.

Supporting information H and 13C NMR spectra for all new compounds are available in Supporting information. Crystallographic data c(CCDC 1502556), 4c (CCDC 1503829), 4f (CCDC 1502557) and 4g (CCDC 1502558) have been deposited at the Cambridge Crystallographic Database Centre. Acknowledgements This work was financially supported by National Natural Science Foundation of China (No. 21372192) and the Priority Academic Program Development of Jiangsu Higher Education Institutions. We also thank the Analysis and Test Center of Yangzhou University for providing instruments for analysis.

References 1. Bohmer, V.: You have full text access to this content calixarenes, macrocycles with (almost) unlimited possibilities. Angew. Chem. Int. Ed. 34, 713–745 (1995) 2. Homden, D.M., Redshaw, C.: The use of calixarenes in metalbased catalysis. Chem. Rev. 108, 5086–5130 (2008) 3. Kim, K., Selvapalam, N., Ko, Y.H., Park, K.M., Kim, D., Kim, J.: Functionalized cucurbiturils and their applications. Chem. Soc. Rev. 36, 267–279 (2007) 4. Xue, M., Yang, Y., Chi, X.D., Zhang, Z.B., Huang, F.H.: Pillararenes, a new class of macrocycles for supramolecular chemistry. Acc. Chem. Res. 45, 1294–1308 (2012) 5. Gutsche, C.D., Muthukrishnan, R., No, K.H., Calixarenes, I.I.: The isolation and characterization of the calix[4]arene and the bishomooxacalix[4]arene from A p-t-butylphenol-formaldehyde condensation. Tetrahedron Lett. 24, 2213–2216 (1979) 6. Gutsche, C.D., Dhawan, B., No, K.H., Muthukrishnan, R.: Calixarenes. 4. The synthesis, characterization, and properties of the calixarenes from p-tert-butylphenol. J. Am. Chem. Soc. 103, 3782–3792 (1981) 7. Dhawan, B., Gutsche, C.D.: Calixarenes. 10. Oxacalixarenes. J. Org. Chem. 48, 1536–1539 (1983) 8. Mckervey, M.A., Seward, E.M., Ferguson, G., Ruhl, B., Harris, S.J.: Synthesis, X-ray crystal structures, and cation transfer properties of alkyl calixaryl acetates, a new series of molecular receptors. J. Chem. Soc. Chem. Commun. 5, 388–390 (1985) 9. Gutsche, C.D., Bauer, L.J.: Calixarenes. 13. The conformational properties of calix[4]arenes, calix[6]arenes, calix[8]arenes, and oxacalixarenes. J. Am. Chem. Soc. 107, 6052–6059 (1985) 10. Arnaud-Neu, F., Cremin, S., Cunningham, D., Harris, S.J., McArdle, P., McKervey, M.A., Ziat, K.: Synthesis, X-ray crystal structure and cation binding properties of a tetrahomodioxacalix[4]arene tetraester. J. Inclusion Phenom. Mol. Recognit. Chem. 10, 329–339 (1991) 11. Zerr, P., Mussrabi, M., Vicens, J.: Isolation and characterization of a new oxacalixarene. Tetrahedron Lett. 32, 1879–1880 (1991) 12. Bavoux, C., Vocanson, F., Perrin, M., Lamartine, R.: New synthesis and complexing properties of p-tert-butyldihomooxacalix[4]arene. Structure of its 1∶2 complex with tetrahydrofuran. J. Incl. Phenom. Mol. Recogn. 22, 119–130 (1995)

13

J Incl Phenom Macrocycl Chem 13. Marcos, P.M., Ascenso, J., Lamartine, R., Pereira, J.C.: Synthesis and NMR conformational studies of p-tertbutyldihomooxacalix[4]-arene derivatives. Supramol. Chem. 6, 303–306 (1996) 14. Marcos, P.M., Ascenso, J.R., Lamartine, R., Pereira, J.L.C.: Conformational studies of tetraalkylated dihomooxacalix[4]arenes. Tetrahedron 53, 11791–11802 (1997) 15. Masci, B., Finelli, M., Varrone, M.: Fine tuning of the cavity size in calixarene-like cyclophanes: a complete series of homooxacalix[4]arene ligands for quaternary ammonium ions. Chem. Eur. J. 4, 2018–2030 (1998) 16. Tomita, K.-I., Suzuki, K., Ohishi, H., Nakanishi, I.: Molecular structure and mutual recognition between host and guest molecules found in the crystal structures of oxacalix[4]arenes complexed with xylene isomers. J. Incl. Phenom. Macrocycl. Chem. 37, 341–357 (2000) 17. Marcos, P.M., Ascenso, J.R., Segurado, M.A.P., Pereira, J.L.C.: Synthesis, NMR conformational analysis, complexation and transport studies of an inherently chiral dihomooxacalix[4]arene triester. Tetrahedron. 57, 6977–6984 (2001) 18. Marcos, P.M., Ascenso, J.R., Pereira, J.L.C.: Synthesis and NMR conformational studies of p-tert-butyldihomooxacalix[4]arene derivatives bearing pyridyl pendant groups at the lower rim. Eur. J. Org. Chem. 17, 3034–3041 (2002) 19. Marcos, P.M., Ascenso, J.R., M.A.P. Segurado, J.L.C. Pereira: p-tert-Butyldihomooxacalix[4]arene/p-tert-Butylcalix[4]arene: transition and heavy metal cation extraction and transport studies by ketone and ester derivatives. J. Incl. Phenom. Macrocycl. Chem. 42 281–288 (2002) 20. Marcos, P.M., Ascenso, J.R.: Synthesis, NMR characterization and ion binding properties of 1,3-bridged p-tert-butyldihomooxacalix[4]crown-6 bearing pyridyl pendant groups. Tetrahedron 62, 3081–3088 (2006) 21. Marcos, P.M., Félix, S., Ascenso, J.R., M.A.P. Segurado, Thuéry, P., Mellah, B., Michel, S., Hubscher-Bruder, V., Arnaud-Neu, F.: Complexation and transport of transition and heavy metal cations by p-tert-butyldihomooxacalix[4]arene tetraketones and X-ray crystal structure of the tert-butyl ketone derivative. New J. Chem. 31, 2111–2119 (2007) 22. Bochenska, M., Cragg, P.J., Guzinski, M., Jasinski, A., Kulesza, J., Marcos, P.M., Pomecko, R.: Ion-selective electrodes based on p-tert-butyl-homooxacalixarene di(ethyl)amides. Supramol. Chem. 21, 732–737 (2009) 23. Gaeta, C., Talotta, C., Farina, F., Teixeira, F.A., Marcos, P.M., Ascenso, J.R., Neri, P.: Alkylammonium Cation Complexation into the Narrow Cavity of Dihomooxacalix[4]arene Macrocycle. J. Org. Chem. 77, 10285–10293 (2012)

13

24. Marcos, P.M., Teixeira, F.A., Segurado, M.A., Ascenso, J.R., Bernardino, R.J., Brancatelli, G., Geremia, S.: Synthesis and anion binding properties of new dihomooxacalix[4]arene diurea and dithiourea receptors. Tetrahedron. 70, 6497–6505 (2014) 25. Marcos, P.M., Teixeira, F.A., Segurado, M.A.P., Ascenso, J.R., Bernardino, R.J., Michel, S., Hubscher-Bruder, V.: Bidentate urea derivatives of p-tert-butyldihomooxacalix[4]arene: neutral receptors for anion complexation. J. Org. Chem. 79 742–751 (2014) 26. Martínez-González, E., Armendáriz-Vidales, G., Ascenso, J.R., Marcos, P.M., Frontana, C.: Site-specific description of the enhanced recognition between electrogenerated nitrobenzene anions and dihomooxacalix[4]arene bidentate ureas. J. Org. Chem. 80, 4581–4589 (2015) 27. Lavendomme, R., Cragg, P.J., Marcos, P.M., Luhmer, M., Jabin, I.: Synthesis of (Homooxa)calixarene–Monoquinones through the “All-but-One” Methodology. Org. Lett. 17, 5690–5693 (2015) 28. Gattuso, G., Notti, A., Parisi, M.F., Pisagatti, I., Marcos, P.M., Ascenso, J.R., Brancatelli, G., Geremia, S.: Selective recognition of biogenic amine hydrochlorides by heteroditopic dihomooxacalix[4]arenes. New J. Chem. 39, 817–821 (2015) 29. Martínez-González, E., González, F.J., Ascenso, J.R., Marcos, P.M., Frontana, C.: Competition between hydrogen bonding and proton transfer during specific anion recognition by dihomooxacalix[4]arene bidentate ureas. J. Org. Chem. 81, 6329–6335 (2016) 30. Talotta, C., Gaeta, C., Rosa, M.D., Ascenso, J.R., Marcos, P.M., Neri, P.: Alkylammonium guest induced-fit recognition by a flexible dihomooxacalix[4]arene derivative. Eur. J. Org. Chem., 158–167 (2016) 31. Yan, C.G., Li, L., Liu, W.L.: Metallic Macrocycle with a 1,3-alternatecalix[4]arene salicylideneamine ligand. J. Coord. Chem. 62, 2118–2124 (2009) 32. Sun, J., Liu, D.M., Wang, J.X., Yan, C.G.: Regioselective synthesis of calix[4]arene 1,3-di and monosubstituted sulfur-containing Schiff bases. J. Incl. Phenom. Macrocycl. Chem. 64, 317–324 (2009) 33. Zhou, R., Ren, J C., Yan, C.G.: Regioselective synthesis of calix[4]arene 1,3-diand monosubstituted sulfur-containing Schiff bases. J. Incl. Phenom. Macrocycl. Chem. 67, 335–342 (2010) 34. Han, Y., Wang, G.L., Sun, J.J., Sun, J., Yan, C.G.: Synthesis and crystal structure of 15a, 20a-di(4-hydroxyphenyl) calix[4]pyrroles and 10a, 20b-di(4-hydroxyphenyl)calix[4]pyrroles. Tetrahedron. 69, 10604–10609 (2013)