Reaction between 1,1-dilithioalkyl phenyl sulphones and ω-bromoesters. Synthesis of cyclic vinyl ethers
Abstract
The reaction between 1,1-dilithioalkyl phenyl sulphones (11) and ethyl 4-bromobutyrate affords tetrahydro-2-furylidene derivatives (13) together with minor amounts of the cyclopropyl ketones (15). A mixture of the cyclohexanone and dihydropyran derivatives (17) and (18), respectively, is obtained by the reaction of (11) with ethyl 5-bromovalerate. Treatment of the ω-bromo-β-ketosulphone (19) with various basic reagents also gives a mixture of (17) and (18).