Silylformylations mechanism

In the first rhodium-catalyzed carbonylative silylcarbocyclization (CO-SiCaC), which was reported in 1992 [12, 13], silylcyclopentenone 9 was isolated as a minor product in the silylformylation of 1-hexyne 8 (Scheme 7.4). Under optimized conditions using Et3SiH and ( BuNC)4RhCo(CO)4 as the catalyst at 60°C, 9 is formed in 54% yield [13]. A possible mechanism proposed for this intermolecular CO-SiCaC is shown in Scheme 7.4 [13]. In this mechanism, the formation of 9 is proposed to proceed via in-... 

Ojima has proposed a mechanism for the rhodium-catalyzed cyclization/silylformylation of enynes that invokes several of the same intermediates proposed for the rhodium-catalyzed cyclization/hydrosilylation of enynes (Scheme 7). Silylmetallation of the G=G bond of the enyne followed by / -migratory insertion of the pendant G=G bond into the resulting Rh-G bond could form rhodium cyclopentyl complex Illf. a-Migratory insertion of GO into the Rh-G bond of Illf followed by silane-promoted reductive elimination from the resulting rhodium formyl complex rVf could release the silylated cyclopentane carboxaldehyde with regeneration of silylrhodium hydride complex If (Scheme 7). 

This mechanism suggests that 288 may be constructed by a similar sequential reaction starting from propargylic alcohols, 70. Under the standard conditions, 70 is silylformylated to give 71, which upon treatment with... 

The tandem silylformylation-allylsilylation of a diallylsilyl ether has been reported by Leighton, using [Rh(acac)(CO)2] as the catalyst (equation 11). This method was optimized and extended to propargylic systems where good diastere-oselectivity can be achieved using the isopropyl derivative. A mechanism is proposed for the stereoselectivity involving coordination of the silicon by both of the oxygen atoms (equation 12). 

The mechanism of the silylformylation reaction, in which silanes (RaSi-H) are substituted for H2, is exactly the same as the mechanism for hydroformylation. 

Problem 6.3. Draw a mechanism for the following silylformylation reaction ... 

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. ... 

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