Silylformylation of Alkynes and Alkenes

Alkenes had been identified as potentially important substrates for silylformylation, but initial attempts using Co2(CO)g as the catalyst produced instead the silyl enol ether 

One of the important advantages of the intramolecular alkene silylformylation reaction as an aldol equivalent is that the products are masked 3,5-dihydroxyalkanals, and therefore that no manipulations are required prior to iteration of the process by aldehyde al-lylation to set up the next intramolecular silylformylation. Given that allylsilanes are well-known aldehyde allylation reagents, intramolecular silylformylation employing a diallylhydrosilane would, in principle, allow for the possibility of a tandem silylformyla-tion/allylsilylation reaction. This has been reduced to practice the diaUylsilyl ethers 60 were subjected to the previously developed silylformylation conditions and the unpuri-fied reaction mixtures were subjected to the Tamao oxidation ]36] to provide triols 61 

The vast majority of the work described in this chapter was reported since 1995. Rho-dium( I)-catalyzed hydroformylation and silylformylation reactions have only very recently been adapted and developed for use in the efficient synthesis of stereochemi-cally complex natural products. In addition, the recent development of tandem reactions that take advantage of the direct production of aldehydes in these carbonylation reactions have only begun to demonstrate the versatility of this chemistry. Rhodium(I)-catalyzed hydroformylation and silylformylation, venerable reactions that have primarily been associated with organometaUic chemistry, must now be considered important tools for natural product synthesis. The continued development of these methodologies for that purpose may be expected. 

A comprehensive list of reviews on other aspects of hydroformylation (refs. 4—35) is provided therein. 

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