Lewis Acid-Promoted Favorskii-Type Ring Contraction of Some Cyclic α-Bromo Ketones and Their Acetals

Article abstract of DOI:10.1055/s-1987-28079

The α-bromo cycloalkyl aryl ketones 2a-d on heating with zinc chloride in methanol furnished in moderate to good yields the ring-contracted products 3a-d having gem methyl carbomethoxy function.The acetals of the related α-bromo ketones 7a-c, lacking the methyl group on the halogen-bearing carbon atom, afforded in acceptable yields the ring-contracted esters 8a-c when heated in protic solvent.The limitation of the present ring-contraction procedure has been discussed.