Dipole-Stabilized Carbanions from Thioesters. Secondary α'-Lithio Carbamates and Tertiary α'-Lithio Thioesters

Article abstract of DOI:10.1021/jo00141a010

The formation of 5 and 17, synthetic equivalents of the α-lithioalkylthio and α-lithiodialkylthio functions, respectively, by deprotonations of the corresponding carbamate 4 and thioester 16 are reported.The reactions of these formally dipole-stabilized carbanions with a variety of electrophiles and their use in synthese of 2,3-substituted thiiranes are demonstrated.The rearrangement of 17 to an α-thiol ketone is shown to be intramolecular by a double labeling experiment.Potentially chiral or conformationally isomeric α'-lithio thioesters are found to be racemized and equilibrated.Formations of secondary α'-lithio thioesters in medium chain, β'-dimethylamino, and allyl systems are reported while β'-alkoxy groups are shown to eliminate to give vinyl thio esters which undergo further metalation.The kinetic acidity of a methyl thioester is shown to be comparable to a propenyl thioester and greater then an ethyl thioester.