Process for the preparation of spiro[2.5]octane-5,7-dione and spiro[3.5]nonane-6,8-dione
This invention relates to methods for the synthesis of spiro[2.5]octane-5,7-dione and spiro[3.5]nonane-6,8-dione which are useful as intermediates in the manufacture of pharmaceutically active ingredients.
1. A method of preparing spiro[2.5]octane-5,7-dione having the formula
said method
comprising:
cyclization of cyclopropylidene carboxylic acid alkyl ester having the formula
with dialkyl 1,3-acetonedicarboxylate having the formula
to form 5,7-dioxo-spiro[2.5]octane-4,6-dicarboxylic acid dialkyl ester having the formula
wherein each R may be independently C1-C6 alkyl,
and
ester hydrolysis and decarboxylation of 5,7-dioxo-spiro[2.5]octane-4,6-dicarboxylic acid to form spiro[2.5]octane-5,7-dione,
wherein each R may be independently C1-C6 alkyl.