Sila anions rearrangement

Phenylthio-l-trimethylsilylalkanes are easily prepared by the alkylation of (phenylthioXtrimethylsilyl)mcthane as shown in Scheme 10 [40], The treatment of (phenylthio)(trimethylsilyl)methane with butyllithium/tetramethylethylene-diamine (TMEDA) in hexane followed by the addition of alkyl halides or epoxides produces alkylation products which can be oxidized electrochemically to yield the acetals. Since acetals are readily hydrolyzed to aldehydes, (phenylthioXtrimethylsilyl)methane provides a synthon of the formyl anion. This is an alternative to the oxidative transformation of a-thiosilanes to aldehydes via Sila-Pummerer rearrangement under application of MCPBA as oxidant [40, 41]. 

Formaldehyde anion synthon ( CHO). The anion of 1 (n-BuLi, THF, 0°) is readily alkylated, particularly by primary halides. The products can he converted into aldehydes under very mild conditions. Oxidation with m-chloroperbenzoic acid gives an unstable sulfoxide, which undergoes an sila-Pummerer rearrangement to an acetal. Addition of water liberates the free aldehyde. Epoxides can also be used as electrophiles.2 3 Example ... 

Allyloxysilyl)lithiums undergo a [2,3]Wittig-type rearrangement smoothly to form allylsilanolate anions in an intramolecular fashion (Scheme 11). This is the first example of the sila-Wittig rearrangement (54g). 

Two groups have reported the use of phenylthiomethyltrimethylsilane as a formyl anion synthon. Alkylation of the lithium anion may be accomplished in THF, or in hexane containing TMEDA. A distinct advantage of this formyl synthon is the ease of unmasking the aldehyde via a sila-Pummerer rearrangement (Scheme 6). However, as steric crowding about the intermediate sulphoxide... 

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