10.3.3.2 Silyl Epoxides

Silyl epoxides can be prepared from vinyl silanes with peroxy acids or from ketones (Scheme 17).

Scheme 17

10.3.5 Peterson Olefination Reaction

Peterson olefination, which is closely related to the Wittig reaction, can be carried out in two ways using either acid or base and the geometry of the alkenes can be controlled accordingly (Scheme 18) .

Scheme 18

Mechanism

The reactions are anti under acidic conditions and syn under basic conditions (Scheme 19). The stereoselectivity is due to involvement of a cyclic transition state under basic conditions, whereas under acidic conditions an acylic mechanism involves.

 

Scheme 19