Rearrangement of radical ipso-intermediates by 1,2-shift of a formyl group. Reactions of adamantyl radicals with thiophencarbaldehydes

Abstract

The reaction of 1-adamantyl radicals with some 5-substituted thiophen-2-carbaldehydes gives rise to the products of adamantyldeformylation; this process is a new example of homolytic aromatic ipso-substitution. Moreover, the reaction with thiophen-2,5-dicarbaldehyde affords, as the major product, 2-(1-adamantyl)thiophen-3,5-dicarbaldehyde in which a formyl group has migrated from the 2- to the 3-position. This result is explained by assuming that the initially formed radical ipso-intermediate rearranges by 1,2-shift of the ipso-substituent.