Metalation and Electrophilic Quenching of C-4 Functionalized Isoxazoles; VIIIPreparation of Derivatives of 5-Thioalkylisoxazoles

The lateral metalation and electrophilic quenching of isoxazoles bearing electron withdrawing groups in the 4-position 1 with disulfides, represents a selective, direct and synthetically useful entry to the thioalkyl derivatives 2 (nine examples). One exception to the formation of monothioalkyl major products was observed for the dianion of 4-[(2-hydroxymethyl-1-pyrrolidinyl)carbonyl]-3,5-dimethylisoxazole (1i) which was found to produce the 5-[bis(phenylthio)methyl]isoxazole derivative 3i as the major isolated product (66%). Oxidation of 2a with 3-chloroperoxybenzoic acid (MCPBA) proceeds selectively at sulfur in the presence of both isoxazole and oxazoline nitrogens to give the corresponding sulfoxide 4a (56%) or sulfone 5a (72%), respectively.