Octacarbonyldicobalt-Diethyl(methyl)silane-Carbon Monoxide1

Co2(CO)8-HSiEt2Me-CO
(Co2(CO)8)

[10210-68-1]  · C8Co2O8  · Octacarbonyldicobalt-Diethyl(methyl)silane-Carbon Monoxide  · (MW 341.94) (HSiEt2Me)

[760-32-7]  · C5H14Si  · Octacarbonyldicobalt-Diethyl(methyl)silane-Carbon Monoxide  · (MW 102.28) (CO)

[630-08-0]  · CO  · Octacarbonyldicobalt-Diethyl(methyl)silane-Carbon Monoxide  · (MW 28.01)

(silyloxymethylenation of alkenes,2 esters,3 and aldehydes;4 silyloxymethylation of epoxides,8 glycosyl acetates,11 benzylic esters,12 and orthoesters;13 carbonylative ring expansion5)

Physical Data: HSiEt2Me: bp 77.4 °C; d204 0.705 g cm-3; n20D 1.3984.

Form Supplied in: HSiEt2Me: colorless oil.

Handling, Storage, and Precautions: see Octacarbonyldicobalt and Carbon Monoxide.

Silyloxymethylenation.

The Co2(CO)8/HSiEt2Me/CO reaction of alkenes results in incorporation of CO to give enol silyl ethers (eq 1).2 The reaction of terminal alkenes such as 1-hexene gives four possible regio- and stereoisomers.2b

The reaction of oxygen-containing compounds with the catalytic system at higher reaction temperatures (140-200 °C) under higher CO pressure (50-80 atm) results in silyloxymethylenation with concomitant cleavage of a carbon-oxygen bond. Esters derived from secondary alcohols are converted to (silyloxymethylene)alkanes (enol silyl ethers), which are useful synthetic intermediates (eq 2).3 The reaction of lactones can proceed at 120-140 °C when pyridine is used as an additive. HSiMe3, Triethylsilane, and Dimethyl(phenyl)silane are also effective for the synthesis of enol silyl ethers. For handling of HSiMe3 (bp 6.7 °C) a special syringe has been devised,4 which should be also useful for storing and handling other low-boiling materials. The reaction of aldehydes affords 1,2-bis(siloxy)alkenes (enediol disilyl ethers) (eq 3).5 Carbonylative ring-expansion of cyclobutanones to 1,2-bis(siloxy)cyclopentenes can also be achieved (eq 4).6

Silylformylation.

Aldehydes are catalytically converted into homologated a-silyloxyaldehydes (eq 5).7 Ring-opening silylformylation of cyclic ethers, including oxiranes, oxetane, and THF, are also effective (eq 6).8

Silyloxymethylation.

The catalytic silyloxymethylation has been revealed to have wide applicability to various oxygen-containing compounds such as oxiranes, oxetanes, tetrahydrofurans, glycosyl acetates, benzylic esters, and orthoesters. The reactions are carried out at near-ambient temperatures (0-40 °C) under 1 atm of CO. Generally, the reaction is faster in the order of HSiMe3 > HSiEtMe2 > HSiEt2Me > HSiEt3. The use of HSiMe3 sometimes causes reduction of substrates, depending on the substrates and solvent used.

Various oxiranes react with HSiEt2Me and CO in the presence of Co2(CO)8 to afford 1,3-diol disilyl ethers with trans ring opening (eq 7).4,9 Stereospecific silyloxymethylation is demonstrated in the reaction of cis- and trans-2-butene oxide. The reactions of oxetanes10 and tetrahydrofurans11 also involve ring-opening silyloxymethylation.

Highly stereoselective silyloxymethylation at the anomeric center of glycosyl acetates can be attained with the Co2(CO)8/HSiMe3/CO catalytic system under mild reaction conditions (eq 8).12 The reaction of benzyl acetates gives b-phenethyl alcohol derivatives (eq 9).13 The reaction is applicable to furanyl-, thienyl-, and ferrocenylmethyl acetates. The reaction of cyclic orthoesters results in CO incorporation to give diols having one additional carbon atom (eq 10).14

Related Reagents.

Carbon Monoxide; Dodecacarbonyltetrarhodium-Dimethyl(phenyl)silane-Carbon Monoxide; Tricarbonylchloroiridium-Diethyl(methyl)silane-Carbon Monoxide.


1. (a) Murai, S.; Sonoda, N. AG(E) 1979, 18, 837. (b) Murai, S.; Seki, Y. J. Mol. Catal. 1987, 41, 197. (c) Murai, S.; Chatani, N.; Murai, T. In Silicon Chemistry; Corey, E. R.; Corey, J. Y.; Gaspar, P. P., Eds.; Horwood: Chichester, 1988; pp 347-355. (d) Murai, S. In Organic Synthesis in Japan: Past, Present and Future; Noyori, R., Ed.; Tokyo Kagaku Dozin: Tokyo, 1992; pp 247-253.
2. (a) Seki, Y.; Hidaka, A.; Murai, S.; Sonoda, N. AG(E) 1977, 16, 174. (b) Seki, Y.; Murai, S.; Hidaka, A.; Sonoda, N. AG(E) 1977, 16, 881. (c) Seki, Y.; Hidaka, A.; Makino, S.; Murai, S.; Sonoda, N. JOM 1977, 140, 361. (d) Seki, Y.; Kawamoto, K.; Chatani, N.; Hidaka, A.; Sonoda, N.; Ohe, K.; Kawasaki, Y.; Murai, S. JOM 1991, 403, 73.
3. Chatani, N.; Fujii, S.; Yamasaki, Y.; Murai, S.; Sonoda, N. JACS 1986, 108, 7361.
4. Murai, T.; Yasui, E.; Kato, S.; Hatayama, Y.; Suzuki, S.; Yamasaki, Y.; Sonoda, N.; Kurosawa, H.; Kawasaki, Y.; Murai, S. JACS 1989, 111, 7938.
5. Seki, Y.; Murai, S.; Sonoda, N. AG(E) 1978, 17, 119.
6. Chatani, N.; Furukawa, H.; Kato, T.; Murai, S.; Sonoda, N. JACS 1984, 106, 430.
7. Murai, S.; Kato, T.; Sonoda, N.; Seki, Y.; Kawamoto, K. AG(E) 1979, 18, 393.
8. Seki, Y.; Murai, S.; Yamamoto, I.; Sonoda, N. AG(E) 1977, 16, 789.
9. Murai, T.; Kato, S.; Murai, S.; Toki, S.; Suzuki, S.; Sonoda, N. JACS 1984, 106, 6093.
10. Murai, T.; Furuta, K.; Kato, S.; Murai, S.; Sonoda, N. JOM 1986, 302, 249.
11. (a) Murai, T.; Hatayama, Y.; Murai, S.; Sonoda, N. OM 1983, 2, 1883. (b) Murai, T.; Kato, S.; Murai, S.; Hatayama, Y.; Sonoda, N. TL 1985, 26, 2683.
12. Chatani, N.; Ikeda, T.; Sano, T.; Sonoda, N.; Kurosawa, H.; Kawasaki, Y.; Murai, S. JOC 1988, 53, 3387.
13. Chatani, N.; Sano, T.; Ohe, K.; Kawasaki, Y.; Murai, S. JOC 1990, 55, 5923.
14. Chatani, N.; Kajikawa, Y.; Nishimura, H.; Murai, S. OM 1991, 10, 21.

Naoto Chatani & Shinji Murai

Osaka University, Japan



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