ELECTROCHEMICAL
PREPARATION
FERROCENYL-CONTAINING L . I. D e n i s o v i c h , and S. P. Gubin
OF
ESTERS
CARBOXYLIC M.
G.
OF
ACIDS
Peterleitner,
UDC
541.13:542.
951.4:547. I'i 3:546.72
P r e v i o u s l y we had shown [1] that the r e a c t i o n of alkyl r a d i c a l s , f o r m e d by the anodic decarboxylation of the anions of m o n o b a s i e oarboxylic acids, with the f e r r i o e n i u m cation, g e n e r a t e d as the s a m e anode, leads to the f o r m a t i o n of a l k y l f e r r o c e n e s . T h i s r e a c t i o n was the f i r s t e x a m p l e of the e l e c t r o c h e m i c a l r e p l a c e m e n t of hydrogen in the v-bonded ligands of t r a n s i t i o n - m e t a l c o m p l e x e s -e-
RCO0 ....
--C02
RCO0"
~ R"
--e-
Et, n - P r , n-ClnI:Ia3)
(R = M e ,
R"
+
(C~Hs)2F e ~-=-x (C5H5) ~ Fe + --> (CsHs)2Fe_ R
/\
-. --I-i+ --~
--e- " N _ _ ~ - Fe +
__~
Fe
\/
It" --~
etc.
\/
It could be e x p e c t e d t h a t the e l e c t r o c h e m i c a l r e p l a c e m e n t of hydrogen in f e r r o c e n e by functional groups is also possible when other carboxylic acids a r e used, and, in p a r t i c u l a r , dibasic a c i d s . In h a r m o n y with this a s s u m p t i o n , in the p r e s e n t p a p e r it was found that the e l e c t r o l y s i s of the anion of oxalic acid and f e r r o cene i n m e t h a n o l at a Pt electrode r e s u l t s in the f o r m a t i o n of the m e t h y l e s t e r s of f e r r o c e n e c a r b o x y l i c and f e r r o c e n e d i c a r b o x y l i c acids, which a r e f o r m e d by the r e a c t i o n of the f e r r i c e n i u m cation with the HOOC" r a d i cals and subsequent e s t e r i f i c a t i o n of the f o r m e d a c i d s . * --e-
--COz
H02CCO~- --~
HO~CCO(
> HO~C"
7.~)\
i
ttO~G" + (C~H~),aFe + - - ~ (C~H~)~Fe--CO~H
-___HH L
\/
!
~ o ~ , Fe (~+) /---N
L\/ ,o
..r
_1
\/
-,,o+
L\!
\/
* It is known [2] that the a c i d - c a t a l y z e d e s t e r i f i c a t i o n of f e r r o c e n e c a r b o x y l i c acids p r o c e e d s e a s i l y .
Institute of H e t e r o o r g a n i c Compounds, A c a d e m y of Sciences of the USSR, Moscow. T r a n s l a t e d f r o m Izvestiya Akademii Nauk SSSR, S e r i y a K h i m i c h e s k a y a , No. 2, pp. 465-468, F e b r u a r y , 1978. O r i g i n a l a r t i c l e submitted May 17, 1977.
0568-5230/78/2702-0403507.50
9
Plenum Publishing C o r p o r a t i o n
403
T A B L E I. R e s u l t s of P h y s i e o c h e m i c a l Studies of E s t e r s of F e r r o cene-Containing Ca.rboxylic Acids
Infrared spec- IMassspectrum trum (u, em-l) m/e)
J(M@,
Compound
Methyl ester of ferroeeneearboxylic acid (mol. wt. 244) Dimethyl ester of 1,1'-ferroeenediearboxylie acid (mol. wt. 302)* /--Carbomethoxypropylferroeene(mol. wt. 286)
lO00, liO0, ~450, i.750
244
i450, i750
302
ltO0, i450, i750 t000, 1t00, 1450, i750 1450, t750
286
t000,
Di(~.earbomethoxypropyl)ferroeene(moL wt. 386) Tri(]e-earbomethoxypropyl)ferroeene(mol. wt. 486)
386 486
*PMR spectrum (6, ppm, in CC14): 4.'/6 t, 4.31 t, 3.80 s.
j "/%--CO,Me
_H + ~ __~
~
~
MeOH
Fe
~
- - C O.,.I:[
(~+)
--
COMe z
Fe
~--CO2Me
In a s i m i l a r m a n n e r , the m o n o - , di-, and t r i ( y - c a r b o m e t h o x y p r o p y l ) f e r r o e e n e s w e r e isolated a f t e r the e l e c t r o l y s i s of a m i x t u r e of f e r r o e e n e and p a r t i a l l y n e u t r a l i z e d glutarie acid s e m i e s t e r . --C 02
MeO~C(CI-I~)3COz---e-~ Me02C(CIs
~ MeO~C(CE2h"
F'~e+ Q-'(CH~)~CO~Me--~ F~/ee --(CH2)3CO~Me
\/ ~
Fe /--x
elC.
\/ The indicated y-carbomethoxypropylferroeenes are formed as a mixture with the suberie acid ester MeO2C(CH2)6CO2Me or Kolbe dimer, the presence of which m a k e s the separation of the reaction products diffioult. T o reduce the yield of the Ko[be dimer the electrolysis was run at a low current density (when compared with electrochemical alkylation), the s a m e as in the additive dimerization reaction [3, 4]. The structure of the obtained products was established via the mass, IR, and PIV[IR spectra (Table I). The dimethyl ester of ferrooenedioarboxylie acid is the I, l'-isomer, since absorption bands in the vicinity of i000 and II00 e m -I are absent in the IR spectrum, while the PMIR spectrum lacks the signal that corresponds to the unsubstituted cyelopentadienyI ring. Consequently, the electron-aooeptor M e O 2 C grouping in the molecule of the ferricenium oation orients the newly entering radical to the unsubstituted oyclopentadienyl ring, the same as in the eleetrophilio substitution reactions of ferroeene derivatives with accepter substituents [5].
As a r e s u l t , the e l e c t r o c h e m i c a l r e p l a c e m e n t of hydrogen in f e r r o e e n e b y caxbomethoxy and ~, - c a r b o methoxyalkyl groups was a c c o m p l i s h e d for the f i r s t t i m e in the p r e s e n t p a p e r . The found method for the p r e p a r a t i o n of the e s t e r s of f e r r o c e n y l - e o n t a i n i n g e a r b o x y l i c acids in one step differs f a v o r a b l y f r o m the known m u l t i s t e p methods for the p r e p a r a t i o n of sirnilar products [6].
EXPERIMENTAL The e l e c t r o l y s i s was run in a cylindrical g l a s s v e s s e l (350 ml), equipped with a s t i r r e r , reflux c o n d e n s er, t h e r m o m e t e r , inlet for" an inert gas (argon), outlet for the gaseous products, and a cooling j a c k e t . The 404
anode was a cylindrical Pt s c r e e n with an operating surface of 0.26 dm 2, while the cathode was Pt foil. distance between the e l e c t r o d e s (4 mm) was fixed b y a Teflon ring:
The
11Methyl E s t e r s of F e r r o c e n e c a r b o x y l i n A c i d s . The e l e c t r o l y s i s of a solution, containing 9.5 g o f f e r r o cene and 25 g of oxalic acid in 280 m l o f abs. MeOH, was run a t a c u r r e n t density of 3.8 A/din 2 and a voltage of 25V at 15~ A f t e r the passage of 0.4 F of e l e c t r i c i t y and reduction with Na2S203 the products were e x t r a c , ted with benzene. The benzene solution was washed in s u c c e s s i o n with Na2CO3 solution and w a t e r , andthen dried over MgSO4. After r e m o v a l of the benzenewe obtained 8.1 g o f products, f r o m which, using T L C on Al203, we isolated 6.18 g (65%) of unreacted f e r r o c e n e (eluant =petroleum e t h e r ) , 0.85 g ( 2 0 % ) * o f m e t h y l f e r r o cenecarboxylate, 0.21 g (4%) of dimethyl 1, l ' - f e r r o c e n e d i c a r b o x y l a t e (einant =benzene), and 0.86 g of uni d e n t f f i e d f e r r o c e n e - c o n t a i n i n g p r o d u c t s (eluant =aqueous KOH solution, with subsequent acidification and ext r a c t i o n with benzene). The obtained e s t e r s were c h a r a c t e r i z e d b y t h e IR, PMR, and m a s s s p e c t r a (see Table 1). 7 - C a r b o m e t h o x y p r o p y l f e r r o c e n e s . The e l e c t r o l y s i s of a solution, containing 8.5 g of f e r r o c e n e and 50 g of the monomethyl e s t e r of glutaric acid, neutralized tothe extent of 40%by the addition of KOH, in 280 m t of abs. MeOH was run at a c u r r e n t density of 2.3 A/din 2 a n d a voltage of 3 V at 20~ A f t e r the passage of 0.3 F of e l e c t r i c i t y , reduction, and extraction with benzene (the benzene e x t r a c t was washed with Na2CO3 solution) we isolated 12.5 g of a dark red oil. The obtained mixture, containing u n r e a e t e d f e r r o c e n e , f e r r o cene derivatives, and the Kolbe d i m e r MeO2C(CH2)6CO2Me, was s e p a r a t e d in various ways. 1) The u n r e a c t e d f e r r o c e n e (1.5 g)was r e m o v e d by v a c u u m - s u b l i m a t i o n . To separate the f e r r o c e n e containing products from the Kolbe d i m e r the residue was oxidized with an HC1 solution of FeCI 3. The aqueous b l u e - g r e e n l a y e r was reduced and extracted with benzene. R e m o v a l of the benzene gave 3.6 g of products, from which by c h r o m a t o g r a p h y on silica gel (eluant =petroleum ether) were isolated an additional 1.0 g of f e r r o c e n e (total amount =2.5 g, 26%) and 2.6 g (24%) of f e r r o e e n e - c o n t a i n i n g e s t e r s as a d a r k r e d oil (eluant = benzene). 2) The reaction mixture was h y d r o l y z e d with 10 N NaOH solution. A f t e r s e p a r a t i n g the u n r e a c t e d f e r r o cene (2.5 g), acidification of the solution, and extraction with benzene we isolated 4 . 2 g of mixed acids, which were then esterified in the presence of Et20 9 BF 3 to give 3,9 g of mixed e s t e r s , f r o m which by c h r o m a t o g r a p h y on silica gel we isolated 2.5 g of f e r r o c e n e - c o n t a i n i n g e s t e r s (eluant = benzene) as a dark r e d oil. A mixture of f e r r o c e n e - c o n t a i n i n g e s t e r s , obtained by methods 1 and 2, was s e p a r a t e d by TLC on silica gel. Here three fractions were isolated with a total weight of 2.33 g. A c c o r d i n g to the IR and m a s s spectra (see Table 1), the 1st fraction is mainly y - c a r b o m e t h o x y p r o p y l f e r r o c e n e (0.7 g, 7%), the 2rid f r a c tion is mainly d i ( y - c a r b o m e t h o x y p r o p y l ) f e r r o c e n e (0.23 g, 1 . 6 ~ , and the 3rd fraction is mainly tri{~/-carbomethoxypropyl)ferrocene (1o4 g, 8%). Due to the close Rf values of the indicated products they could not be separated completely, as is evidenced by the GLC analysis data obtained for the three f r a c t i o n s . 3) The reaction m a s s was c h r o m a t o g r a p h e d on silica gel. Here we isolated a mixture (6.6 g) of f e r r o c e n e and f e r r o c e n e - c o n t a i n i n g e s t e r s . The subsequent separation of this mixture by T L C on silica gel leads to analogous r e s u l t s .
CONCLUSIONS i . The electrochemical preparation of the methyl esters of ferrocene-containing carboxylic acids was accomplished for the first time. 2. In the studied electrochemical reaction the electron-acceptor substituent in the molecule of the ferriceninm cation orients the newly entering radical to the unsubstituted cyclopentadienyl ring. LITERATURE 1. 2. 3. 4.
CITED
N . B . Zakurin, S. P. Gubin, and L. I. Denisovich, J . Organometal. C h e m . , 129, 203 (1977). K . L . Rinehart, R. J . Curby, and P. E. Sokol, J . Am. Chem. S o c . , 79, 3420 (1957). M. Ya. Fioshin, L. A. Mirkind, L. A. Salmin, and A. G. Kornienko, Zh. V s e s . Khim. Obshchestva im. D. I. Mendeleeva, 10, 238 (1965). M. Ya. Fioshin, A~ I. Kamneva, L. A. Mirkind, and L. A. Salmin, Dokl. Akad. Nauk SSSR, 138, 173 (1961).
* The yields of the products are based on r e a c t e d f e r r o e e n e .
405
5, 6.
E. G. P e r e v a l o v a and T . V. Nikitina, Organometal. Reactions, 4, 185 (1972). R . A. Benkeser, D. Goggin, and G. Sehroll, J . Am. Chem. S e e . , 7_66, 4025 (1954).
REACTION ACIDS
WITH
OF
~-MERCAPTOCARBOXYLIC
ORTHOESTERS
Y u . A. D a v i d o v i e h , a n d S. V. R o g o z h i n
L. A.
UDC 542.91:547.299:547.29-325'26
Pavlova,
The r e a c t i o n of o r t h o f o r m i c e s t e r with carboxylic acids leads to the e s t e r i f i c a t i o n of the latter [1]. Data also exist on the p r e p a r a t i o n of some 1 , 3 - d i o x o l a n - 4 - o n e s b y t h e condensation of ethyl orthoformate with a~-hydroxycarboxylic acids [2]. The p r e s e n t communication is devoted to the reaction of aliphatic o r t h o e s t e r s with a~-mereaptoearboxylie acids, whichwas not studied previously. We established that aliphatic o r t h o e s t e r s r e a c t easily with m e r c a p t o e a r b o x y l i c acids to give the p r e viously unknown 1 - o x o - 2 - a l k o x y - 3 - t h i o l a n - 5 - o n e s in high yield [3].
OR~ HSCHCOOH+ R1C--OR%_ ~ / t
R
\
O--C
RI
\el oRJ
\
//
o
I
+ 2R2OH
OR~ S CHR R = H , CH3; RI=H, CH3; R2=C2Hs
Based on the lit s p e c t r o s c o p y data, the r e a c t i o n begins even at r o o m t e m p e r a t u r e and is completed by refluxing the r e a c t i o n mixture for a short t i m e . The obtained compounds are liquids that can be easily distitled in vacuo without decomposition (Table 1). The s t r u c t u r e of the obtained compounds was confirmed by the elemental analysis data and the lit s p e c t r a , in which an intense absorption band is p r e s e n t in the 17901780 cm -1 region, which is c h a r a c t e r i s t i c for the stretching vibrations of the carbonyl group of an oxothiolane ring. The obtained compounds can be u s e d s u c c e s s f u l l y [4] to synthesize the biologically active amides of ~m e r e a p t o c a r b o x y l i c acids and t h e i r s t r u c t u r a l analogs of the following type: o HSCHC// I \ R1
NHR 2
EXPERIMENTAL 1 - O x o - 2 - e t h o x y - 3 - t h i o l a n - 5 - o n e (I). A mixture of 0.083 mole of thioglycolic acid and 0.166 mole of ethyl o r t h o f o r m a t e was kept for a day at ~20 ~ and then subjected to fractional distillation in vacuo. The f r a c tion with bp 77-78 ~ (1 mm) was identified to be (I). In a s i m i l a r m a n n e r , 1 - o x o - 2 - m e t h y l - 2 - e t h o x y - 3 - t h i o l a n TABLE I .
1-Oxo-2-alkoxy-3-thiolan-5-ones
Corn-IYield.lbp. *C pound .v. (p, mm / of Hg) (I) (II) (III)
Found, % no
c
94,0 77-78(1) t,4790 40,49 92,5 55(1) 1,4726 44,65 94,0 83-85(4) 1,47i3 44,63
I
I rl
s
Empiri- Calculated,% cal "formula c ii s
40,53 5,47 I 21,35 CsHaO3S C~tt,00~S 44,42 6,30 C~HI003S 44,42 6,20
iTIR i spectrun
i(v,
cm ~
5,44 21,63 1790 6,t6 t780 6,i6 1780
Institute of H e t e r o o r g a n i c Compounds, A c a d e m y of Sciences of the USSR, Moscow. T r a n s l a t e d from I z v e s t i y a Akademii Nauk SSSR, S e r i y a Khimicheskaya, No. 2, pp. 468-469, F e b r u a r y , 1978. Original article submitted May 23, 1977.
406
0568-5230/78/2702-0406507.50
9
Plenum Publishing Corporation