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[3.5]nonane-6,8-dione having the formula
said method comprising:
cyclization of cyclobutylidene carboxylic acid alkyl ester having the formula
with dialkyl 1,3-acetonedicarboxylate having the formula
to form 6,8-dioxo-spiro[3.5]nonane-5,7-dicarboxylic acid dialkyl ester having the formula
wherein each R may be independently C1-C6 alkyl,
and
ester hydrolysis and decarboxylation of 6,8-dioxo-spiro[3.5]nonane-5,7-dicarboxylic acid dialkyl ester having the formula
to form spiro[3.5]nonane-6,8-dione,
wherein each R may be independently C1-C6 alkyl.