Bifunctional allylsilanes

A bifunctional allylsilane reagent has been developed in which an initial nucleophilic attack at an acetal centre, mediated by trimethylsilyl trifluoromethanesulfonate(TMSOTf). is followed by cyclization of the allylsilane portion onto an electrophilic site, mediated by titanium(IV) chloride11. 

Scheme 3-159. Methylene cyclohexane synthesis using bifunctional allylsilanes and acetals.

Acetoxymethyl-3-allyltrimethylsilane is a bifunctional or conjunctive reagent that provides an efficient and versatile means of synthesizing methylenecyclopentanes via [3 + 2] cy-cloaddition18 In the presence of catalytic amounts of an appropriate palladium(O) complex, the combination of the allyl acetate and allylsilane functionalities results in the formation of a metal-stabilized trimethylenemethane unit (TMM-Pd). This is able to undergo Smooth [3 + 2] cyeloaddition reactions with electron-deficient olefins. 

Tran -nitroso dimers have been prepared by the reaction of thionitrate esters with (9-acyl derivatives of A-hydroxyl-2-thiopyridines (Scheme 28)., The potential-energy surface for the reaction of the fluoroformyl radical [FC(0)] with NO has been calculated using ab initio studies at the B3LYP level. The reaction was calculated to proceed via addition to NO to form an FC(0)N0 adduct which upon fragmentation yielded FNO and CO. Photo-induced electron-transfer reactions between allylsilane-allylstannane bifunctional reagents and 1,2-diketones have been shown to give a-keto homoallylic alcohols having an allylsilane moiety. 

In a further example of the power of bifunctional annulating reagents, the allylsilane (79) (Scheme 8) has been shown to be an excellent cyclopentane precursor. Two modes of reaction are possible. First, conversion into a cuprate and addition to an enone gave the allylsilane (80), which can be cyclized to a... 

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