ORGANIC
LETTERS
2000
Vol. 2, No. 8
1027-1029
An Efficient Pd-Catalyzed Route to Silyl
Esters
Moni Chauhan, Bhanu P. S. Chauhan, and Philip Boudjouk*
Center for Main Group Chemistry, Department of Chemistry, North Dakota State
UniVersity, Fargo, North Dakota 58105
Received January 4, 2000
ABSTRACT
A one-step, highly selective catalytic route to silyl esters is reported. Commercially available silanes with Si-H functionality were converted
to silyl or siloxy esters in the presence of Pd(OAc)2 under mild reaction conditions. This protocol was found to be equally applicable for the
modification of multiple silicon centers in one framework and lead to the corresponding polysilyl esters in high yields. A comparison of
catalytic efficiency of Pd(OAc)2 versus Pd on carbon was also undertaken.
Simple methods for the quantitative conversion of a variety
of organic compounds into stable, easily isolable and
identifiable silyl derivatives are required in organic synthe-
sis.1 The silylating agents generally used in the conversion
of the carboxyl function to the silyl ester group are
aminosilanes which require prolonged heating and continuous
removal of ammonia or amine.2 Other important methods
to synthesize silyl esters are by heating chlorosilanes or
alkoxysilanes with acetates or acetic anhydrides.3 However,
these processes are applicable under extreme reaction condi-
tions and are accompanied by side products.
The utility of introducing functional groups on a polysi-
loxane backbone is well recognized, and modifying the
existing ones is a continuous challenge. Organofunctional
polysiloxanes couple the unique properties of polysiloxanes
with the wide range of reactivities of carbon functional
organic groups.4 The degradation properties of polysilyl
esters have received considerable interest in environmental
and biomedical applications.5 A few of the many applications
of polysilyl esters are in the cotton textile industry to impact
water repellency6 as liquid cross-linkers, adhesion promoters,
and as a source of silicon dioxide.7 Polysiloxanes bearing
silyl ester end groups have also been used as protection
agents in anionic polymerization8 and in photographic
applications9 and as viscosity reduction agents.10 Although
a wide range of transition metal catalysts have been reported
for dehydrocoupling of OH-containing compounds with
silanes,11 there are only a few examples of COOH/SiH
dehydrocoupling reactions.12 We report herein a very simple,
efficient, catalytic route for quantitative conversion of silanes
(4) Chauhan, B. P. S.; Boudjouk, P. Tetrahedron Lett. 1999, 40, 4123.
Arruda, A. F.; Campiglia, A. D.; Chauhan, B. P. S.; Boudjouk, P. Anal.
Chim. Acta 1999, 396, 263.
(5) Peppas, N. A.; Langer, R. Science 1994, 263, 1715; Langer, R. Acc.
Chem. Res. 1993, 26, 537. Weinberg, J. M.; Gitto, S. P.; Wooley, K. L.
Macromolecules 1998, 31, 15.
(6) Patrode, W. I. U.S. Patent 2,306,222, December 22, 1942. (b) Barry,
A. J. U.S. Patent 2,405,988, August 20, 1946.
(7) Kendrick, T. C.; Parbhoo, B.; White, J. W. The Chemistry of Organic
Silicon Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley & Sons
Ltd.: New York, 1989; Chapter 21.
(8) Mormann, W.; Schwabe, A.; Sikora, R. Makromol. Chem. 1986,
187, 133. Morshima, Y.; Hashimoto, T.; Itoh, Y.; Kamachi, M.; Nozakura,
S. J. Polym. Sci., Polym. Chem. Ed. 1982, 20, 299.
(1) Pierce, A. E. Silylation of Organic Compounds; Pierce Chemical
Co.: Rockford, IL, 1968. Colvin, E. Silicon in Organic Synthesis;
Butherworths: London, 1981. Haslam, E. Tetrahedron 1980, 36, 2409.
(2) Aizpurua, J. M.; Palomo, C.; Palomo, A. L. Can. J. Chem. 1984, 62,
336. Palomo, A. L. An. Quim.. 1981, 77(1), 35. Palomo, A. L.; Palomo, C.
An. Quim. 1981, 77(1), 87. Palomo, C. Synthesis. 1981, 809. Aizpurua, J.
M.; Palomo, C. Bull. Soc. Chim. Fr. II. 1982, 265.
(3) Mbah, G. C.; Speier, J. L. J. Organomet. Chem. 1984, 271, 77.
Schuyten, H. A.; Weaver, J. W.; Reid, J. D. J. Am. Chem. Soc. 1947, 69,
2110. Sauer, R. O.; Patnode, W. J. Am. Chem. Soc. 1945, 67, 1548.
Anderson, H. H.; Fischer, H. J. Org. Chem. 1954, 19, 1296.
(9) Shirai, M.; Miwa, T.; Tsunooka, M. Chem. Mater. 1995, 7, 642 and
references therein. Aoai, T. (Fuji Film Co. Ltd.) Eur. Pat. Appl. EP010599,
January 9, 1985; JP Appl. 83/117 769, June 29, 1983.
(10) Greber, G.; Darms, R. Gen. Offen. DE 2206359 720907.
10.1021/ol005507t CCC: $19.00 © 2000 American Chemical Society
Published on Web 03/29/2000