Oxidative addition of trifluoroacetamide to alkenes, 2,5-dimethylhexa-2,4-diene and conjugated cyclic dienes

Abstract

Reactions of trifluoroacetamide with alkenes and dienes were studied in an oxidative system (t-BuOCl+NaI). With styrene, p-chlorostyrene and vinylcyclohexane the products of iodoamidation, 2,2,2-trifluoro-N-(2-iodo-1-R-ethyl)acetamides, were obtained. With linear diene, 2,5-dimethylhexa-2,4-diene, the product of successive addition-cyclization, trans-2,2,2-trifluoro-N-(4-iodo-2,2,5,5-tetramethyltetrahydrofuran-3-yl)acetamide was formed, whose structure was proved by X-ray analysis. With conjugated cyclic dienes, cyclopentadiene and cyclohexa-1,3-diene the adducts of the active intermediate formed from trifluoroacetamide, CF3CONHI, to only one double bond are formed, the structure of the latter adduct also being proved by X-ray analysis. In contrast, cyclooctadiene-1,3 affords the product of addition of two iodine atoms, hydroxy group and the trifluoroacetamide residue to the two double bonds. Their relative positions in the formed tetrasubstituted cyclooctane derivative were determined by homo- and heteronuclear NMR techniques, which allowed to assign the product the structure of 2,2,2-trifluoro-N-(3-hydroxy-2,8-diiodocyclooctyl)acetamide.