Epoxysilanes synthesis

During studies directed towards the synthesis of spatol, Salomon and Murthi studied epoxysilane 153 bearing a temporary tether (Scheme 5.36), which circumvented the potential problem of configurational instability described above [57]. 

In their synthesis of (+)-cerulenin, Mani and Townsend employed lithiated epoxysilane 157, which they trapped with (4E,7 )-nonadienal to give a 77% yield of 158, which was further manipulated to give the natural product (Scheme 5.37) [58], as-ot, 3-Epoxy-Y,S-vinylsilanes 159 are regioselectively lithiated at the a-silyl position, and can subsequently be stereo selectively trapped with a range of electrophiles to give a-substituted epoxyvinylsilanes 160, which can in turn be isomerized to a-silyl-P-vinylketones 161 (Scheme 5.38) [59]. 

Hodgson, D. M. Norsikian, S. L. M. First direct deprotonation-electrophile trapping of simple epoxides synthesis of a,/f-epoxysilanes from terminal epoxides. Org. Lett. 2001, 3, 461—463. 

Nucleophilic substitution of a,/3-epoxysilanes followed by the Peterson elimination is valuable for the stereoselective synthesis of alkenes.3 The reactions with lithium phenylsulfide and diphenylphosphide form alkenyl sulfides and alkenylphosphines, respectively, in a stereospecific manner. 7-Metallo-a,/ -epoxysilanes are isomerized to a-siloxyallylmetals by anionic ring opening and subsequent Brook rearrangement (Equation... 

The isomeric epoxysilanes (3) and (4), prepared as shown in Scheme 6, undergo a copper-catalyzed Grignard ring-opening to give P-hydroxysilanes. Oxidative cleavage then completes this selective route to either syn (5) or anti (6) 1,2-diols. Such methodology has been utilized in a synthesis of ( )-cj o-brevi-comin. 

An optically active silyl-stabilised lithiated epoxide has been used in the synthesis of (-F)-cerulenin 111 (Scheme 21) [73]. Starting from the epoxysilane 107, obtained in high enantiomeric purity via Sharpless epoxidation of 106, deprotonation by s-BuLi TMEDA was followed by electrophile trapping using (4E,7E)-nonadienal 109 to allow a concise preparation of 110, which is a key intermediate in the (-F)-cerulenin synthesis. 

Organofunctional epoxysilanes may be prepared by hydrosilylating unsaturated epoxides or epoxidized unsaturated silanes. The hydrosilylation of allyl ethers CH2=CHCH20R is commonly used for synthesis (e.g., y-glycidoxytrimethoxysilane) as follows ... 

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