Hydrosilane-mediated reactions

Hydrosilylation of alkenes or dienes comprises of addition of hydrosilanes to a C-C double bond mediated by a catalyst, usually an organometallic compound. These reactions have been the subject of two comprehensive reviews1 2. 

In studies on stoichiometric reactions of hydrosilanes with zirconocene and hafirocene derivatives containing M-Si or M-H bonds, it was found that o-bond metathesis processes readily occur. Thus, 4-center transition states containing a d metal center, hydrogen, and silicon easily form and mediate facile bond-making and bond-breaking processes involving these components. 

Reductive aldol reaction of a,(5-unsaturated esters and enones with aldehyde mediated by a transition metal hydride complex and a hydride source, such as hydrosilane, is a versatile process to produce p-hydroxy carbonyl compounds (Scheme 15a) [21]. This reaction is thought to be an alternative transformation of Lewis acid-catalyzed Mukaiyama-type aldol reaction with silyl enol ethers or silyl ketene acetals (Scheme 15b). 

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