Russian Journal of General Chemistry, Vol. 71, No. 1, 2001, pp. 1473148. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 1, 2001, pp. 1613162. Original Russian Text Copyright C 2001 by Panarina, Dogadina, Ionin.
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Addition of tert-Butylamine to Diethyl Alkynephosphonates Catalyzed by CuCl A. E. Panarina, A. V. Dogadina, and B. I. Ionin St. Petersburg State Institute of Technology, St. Petersburg, Russia Received September 21, 2000
2-Dialkylaminoalkenephosphonates are of interest as model compounds in the study of the mechanism of certain biochemical processes [1], as precursors of b-keto phosphonates widely used in the Horner 3Emmons reactions [2], and for the synthesis of cyclic and acyclic compounds [3, 4]. Reaction of primary amines with 1,2-alkadienephosphonates is known to yield a mixture of geometric isomers of 2-alkylaminoalkenephosphonates [5]. Addition of primary amines to acetylenic phosphonates has not been studied. We found that reaction of diethyl alkynephosphonates with primary amine, namely, tert-butylamine, proceeds in the presence of catalytic amounts of CuCl at ca. 100oC. Addition is regio- and stereoselective and yields exclusively the E isomers of diethyl 2-(tertbutylamino)alkenephosphonates IIa3IIc.
g ggggeikei ggg (EtO)2PC=CR + H2NBu-t
MeOH, T o Cu(I)Cl
-
O I
-
O
776 (EtO)2P
To
76 IIa3IIc E, Z
R
C C
-
H
NHBu-t
(E )-IIa3IIc
-
R = Me, Et, Ph.
The purity of compounds (E)-IIa3IIc follows from their 1H, 31P, and 13C NMR and IR spectra. The olefinic proton in enamines (E)-IIa3IIc gives a doublet at d 3.93 4.4 ppm (2JHP 9.6 310.6 Hz); in the 13C NMR spectrum, there are doublets at dC, ppm: 71.53 84.4 (C1, 1JPC 188.33216.8 Hz), 149.0 3169.9 (C2, 2 JPC 5.0 319.3 Hz), and 21328 (IIa, IIb) or 138.8 (IIc) (C3, 3JPC 5.036.7 Hz). The measured constants 3 JPC are characteristic of compounds with cis arrange-
ment of the phosphorus and carbon atoms at the double bond in enamines and unequivocally prove the E configuration of the addition products [6, 7]. However, after deep-vacuum distillation, which proceeds with partial decomposition of enamines, we isolated a mixture of E and Z isomers of diethyl 2-(tertbutylamino)alkenephosphonates IIa3IIc in a 65 : 35 ratio with a total yield of 553 65%. Formation of the isomeric mixture can result from tautomeric transformations at elevated temperatures:
g
g
g
76 (EtO)2PCH2C(R)=NHBu-t (EtO)2PCH=CRNHBu-t 4
O
E
O
76 (EtO)2PCH=CRNHBu-t. 4
O
E, Z
The 1H NMR spectra of the distilled compounds contain two doublets of methine proton at d 3.93 4.4 (2JHP 9.6 310.6 Hz) and 3.4 33.9 ppm (2JHP 12.53 14.0 Hz), corresponding to the E and Z isomers of enamines IIa3IIc. The 13C NMR spectra contain two doublets of the C3 atom in relatively strong field, trans 5.0 3 with typical vicinal coupling constants 3JPC 3 cis 6.7 and JPC 21322.0 Hz [6, 7].
gg
Enamines IIa3IIc are easily hydrolyzed to form the corresponding b-keto phosphonates: H2 O
IIa3c 76 (C2H5O)2PCH2CR. O
O
IIIa, b
Diethyl N-tert-butylaminoalkenephosphonates were prepared by heating of 0.01 mol of the corresponding diethyl alkynephosphonate I, 0.011 mol (10% excess) of tert-butylamine, and 0.1 g (5% of
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the amount of I) of CuCl in 3 ml of absolute methanol in a sealed ampule. The ampules were kept at 100 3 110oC for 10 330 h. The reaction progress was monitored by 1H NMR spectroscopy until the initial alkynephosphonate was consumed completely. The solvent was removed in a vacuum, and the residue was distilled in a deep vacuum. b-Enaminophosphonates are yellow oily liquids. In the course of distillation the compounds partially decompose, and the yield significantly decreases. Diethyl N-tert-butylaminopropenephosphonate IIa. Yield 57%, bp 1523155oC (0.4 mm Hg). IR spectrum (KBr), n, cm31: 2970, 1587 (C=C), 1200 (P=O), 1013. 1H NMR spectrum (CDCl3), d, ppm: 1.18 t (6H, CH3), 1.28 m (9H, CH3, t-Bu), 1.99 s (3H, CH3-E), 2.01 s (3H, CH3-Z), 3.41 d (1H, CH-Z, 2JHP 13.4 Hz), 3.9 d (1H, CH-E, 2JHP 10.6 Hz), 3.95 q (4H, CH23O). 13 C NMR spectrum (CDCl3), dC, ppm: 16.08 (CH3), 21.35 d (CH3-E, 3JPC 5.0 Hz), 22.86 d (CH3-Z, 3JPC 22.14 Hz), 28.41 (CH3, t-Bu-E), 30.87 (CH3, t-Bu-Z), 50.98 (C, t-Bu-E), 51.4 (C, t-Bu-Z), 60.36 (CH23O, E), 62.17 (CH23O, Z), 72.63 d (CH-Z, 1JPC 192.3 Hz), 74.80 d (CH-E, 1JPC 210.0 Hz), 156.1 d (=C3N, E, 2 JPC 19.32 Hz), 163.57 d (=C3N, Z, 2JPC 5.79 Hz). 31 P NMR spectrum (CDCl3), dP, ppm: 25.51 (E), 26.13 (Z). Diethyl N-tert-butylaminobutenephosphonate IIb. Yield 55%, bp 1623164oC (0.4 mm Hg). IR spectrum (KBr), n, cm31: 2974, 1580 (C=C), 1200 (P=O), 1013. 1H NMR spectrum (CDCl3), d, ppm: 1.08 t (3H, CH3), 1.25 t (6H, CH3), 1.27 m (9H, CH3, t-Bu), 2.37 q (2H, CH2-E), 2.57 q (2H, CH2-Z), 3.53 d (1H, CH-Z, 2JHP 12.6 Hz), 3.91 d (1H, CH-E, 2JHP 9.6 Hz), 3.95 q (4H, CH23O). 13C NMR spectrum (CDCl3), dC, ppm: 13.51 (CH3, Et), 16.07 (CH3), 27.17 d (CH2, Et-Z, 3JPC 20.97 Hz), 28.03 d (CH2, Et-E, 3JPC 6.7 Hz), 28.46 (CH3, t-Bu-E), 31.05 (CH3, t-Bu-Z), 50.76 (C, t-Bu-E), 51.52 (C, t-Bu-Z), 60.44 (CH23O, E), 62.31 (CH23O, Z), 71.57 (CH-Z, 1JPC 193.9 Hz), 74.06 d (CH-E, 1JPC 215.45 Hz), 161.83 d (=C3N, E, 2JPC 19.22 Hz), 169.92 d (=C3N, Z, 2JPC 6.2 Hz). 31 P NMR spectrum (CDCl3), dP, ppm: 26.53 (E), 27.47 (Z).
Diethyl N-tert-butylaminophenylethenephosphonate IIc. Yield 65%, bp 166 3170oC (0.1 mm Hg). IR spectrum (KBr), n, cm31: 2986, 1593 (C=C), 1253 (P=O), 1026. 1H NMR spectrum (CDCl3), d, ppm: 1.09 s (9H, CH3, t-Bu), 1.24 t (6H, CH3), 3.93 d (1H, CH-Z, 2JHP 14.09 Hz), 4.05 q (4H, CH23O), 4.37 d (1H, CH-E, 2JHP 10.08 Hz), 7.2937.45 m (5H, arom.). 13 C NMR spectrum (CDCl3), dC, ppm: 16.11 (CH3), 29.49 (CH3, t-Bu-E), 31.84 (CH3, t-Bu-Z), 51.66 (C, t-Bu-E), 53.39 (C, t-Bu-Z), 61.81 (CH23O, E), 62.41 (CH23O, Z), 77.7 d (CH-E, 1JPC 216.84 Hz), 84.4 d (CH-Z, 1JPC 188.3 Hz), 127.383127.7 (CH arom., E), 128.393128.83 (CH arom., Z), 138.76 d (Cipso arom., E, 3JPC 2.76 Hz), 140.7 d (Cipso arom., Z, 3JPC 19.9 Hz), 155.42 d (=C3N, Z, 2JPC 16.59 Hz), 164.46 d (=C3N, E, 2JPC 6.08 Hz). 31P NMR spectrum (CDCl3), dP, ppm: 23.57 (Z), 24.2 (E). The IR spectra were taken on a Specord IR-75 instrument from thin layers on KBr. The NMR spectra were registered on a Tesla BS-497 instrument (100 Mz) using 1H3{31P} NMDR technique, with HMDS as external reference. The 1H, 31P, and 13C NMR spectra were registered on a Bruker AC-200 instrument, with 85% H3PO4 as external reference and CDCl3 as internal reference. REFERENCES 1. Lee, S.-L., Hepburn, T.W., Swartz, W.H., Ammon, H.L., Mariano, P.S., and Dunaway-Mariano, D., J. Am. Chem. Soc., 1992, vol. 114, pp. 7346 37354. 2. Walker, B.J. Organophosphorus Reagents in Organic Synthesis, Cadogan, J.G.G., Ed., Academic, 1979, issue 4, pp. 1553206. 3. Palacios, F., Garcia, J., Ochoa de Retana, A., and Oyarzabal, J., Heterocycles, 1995, vol. 41, p. 1915. 4. Lopez, F., Pelaez, E., Palacios, F., Barluenga, J., Garcia, S., Tejerina, B., and Garcia, A., J. Org. Chem., 1994, vol. 59, p. 1984. 5. Palacios, F., Aparicio, D., and Gareia, J., Tetrahedron, 1996, vol. 52, no. 28, pp. 960939628. 6. Palacios, F., Ochoa de Retana, A.M., and Oyarzabal, J., Tetrahedron, 1999, vol. 55, pp. 309133104. 7. Duncan, M. and Gallagher, M.J., Org. Magn. Reson., 1981, vol. 15, no. 1, pp. 373 42.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY
Vol. 71
No. 1
2001
