Allyloxysilanes, retro-1,4-Brook rearrangement

The [1,4]-rearrangement of the allyloxysilane system is a potentially useful method for allylsilane synthesis (equation 106). However, in general, a [1,2]-rearrangement may occur predominantly in this system (see Section n.F.l). To this end, the author s group recently found that the rearrangement of 171 in the presence of excess amount of HMPA provides the [l,4]-retro-Brook rearrangement product 172 in excellent yield (equation 107). ... 

The asymmetric retro-[l,4] Brook rearrangement of allyloxysilane using 582 (R = C00C6H4-/)-N02) as electrophile and its stereochemical course at silicon to give 592 have been evaluated <2006AGE2235>. 

Under carefully optimized conditions, including addition of HMPA to the reaction mixture, deprotonation of allyloxysilanes favored the retro-1,4-Brook rearrangement. The method was applied to systems having an asymmetric center at silicon (e.g., 160), and it was shown that the rearrangement occurred with retention of configuration at silicon. " ... 

A mechanistic study of the retro-[1,4]-Brook rearrangement of 3-silyl allyloxysilanes is reported to explain why acidic hydrolysis gives the enol, whereas basic hydrolysis gives the aldehyde (Scheme 62)P... 

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