Alkynes silylcarbonylation

Reactions of alkynes with hydrosilanes under CO (1-30 atm) catalyzed by Rh4(CO),2 or Rh2Co2(CO),2 give /3-formylvinylsilanes in high to excellent yields . This reaction, silylformylation, is dso a silylcarbonylation, but it proceeds via a different mechanism from the Co2(CO)8-catalyzed silylcarbonylation. In fact, Co2(CO)g is inactive for silylformylation. The reaction catalyzed by Co2Rh2(CO),2 is proposed to involve the Co-Rh mixed metal dinuclear complexes as active catalyst species. ... 

Silylformylation of terminal alkynes generally occurs under relatively mild conditions to afford a silylolefm. The major side product of this reaction is hydrosilylation. The use of more reactive organosilanes or an increase in the carbon monoxide pressure has been shown to enhance silylformylation. Furthermore, Doyle and Shankin demonstrated that a dirhodium complex can be used to overcome this synthetic problem. Dirhodium(II) perfluorobut3n ate has been shown to give exclusively silylcarbonylation when used with phenylacetylene 70 favoring the cis product with Z E ratios as high as 40 1 (71a and 71b). Additional success with... 

Although for the catalytic transformations of organosilicon compounds only hydrosilylation is well known as industrially important process, in the last 20 years other reactions of silicon compounds catalyzed by transition metal complexes have been discovered and developed. They include double (bis)silylation of alkenes and alkynes, silylative coupling of alkenes and alkynes with vinylsi-lanes, dehydrocoupling of hydrosilanes, silylformylation and silylcarbonylation of unsaturated compounds, and dehydrogenative silylation of alkenes and alkynes with hydrosilanes. Only the latter, as related to hydrosilylation (and very often its side reaction), has been discussed here (13). 

Rh catalyses the hydrosilylation of alkenes and the dehydrogenative silylation of 1,5-dienes and alkynes, and the silylcarbonylation of alkynes to give p-silylacrylaldehydes with exceptional stereocontrol , ketones and enones give silyl enol ethers, 1,3-cyclobutane dione gives 3-hydroxycyclobutanone, and assists in the silylformylation of ethynyl pyirolidone derivatives to give pyrrolizidine alkaloids, and epoxides to give p-siloxy aldehydes, and... 

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