Methyl silyloxycyclopropanecarboxylates

Alkylation of cyclopropanecarboxylic acid esters,6 Deprotonation of methyl silyloxycyclopropanecarboxylates (1), prepared as shown, is possible with LDA in THF at — 78°. The resulting anions react with primary alkyl iodides and benzylic or allylic bromides to give 2 in high yield. These products are cleaved by F to methyl 4-ketocarboxylates 3. 

Silyloxycyclopropanecarboxylates are masked homoenolate equivalents which can also add to dimethyl(methylene)iminium salts. In one of several examples reported by Reissig and Lorey, methyl 2-f-butyl-2-(trimethylsilyloxy)cyclopropanecarboxylate and triflate salt (33) react to produce methylaminomethyl-y-oxo ester (64 Scheme 14). The reactive intermediate has not been precisely determined but is most likely a ring-opened enolate (63) or its silyl ketene acetal derivative. The reaction can also be performed using the chloride iminium salt (31) in the presence of TiCU, but the reproducibility is poor due to reduced solubility. The products of these reactions are convenient precursors to a-methylene-8-lactones and acrylic acid derivatives. 

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See also in sourсe #XX -- [ ]

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