Ring expansions of 1-haloethynyl-2-methylcyclopentanols

Article abstract of DOI:10.1016/0040-4020(96)00561-3

1-Haloethynyl-2-methylcyclopentanols treated with iodine and HTIB ring expand stereoselectively depending on the relative position of the methyl and the hydroxyl groups. The products are 2-(dihalomethylidene)-3-methylcyclohexanones if the methyls are cis to the hydroxyl groups or 2-(dihalomethylidene)-6-methylcyclohexanones if the methyls are trans to the hydroxyls.