Skeletal Modification of Benzothiophene Mediated by Iron Carbonyls: Insertion of Terminal Alkynes with Migration of Amino and Alkoxy Groups

Abstract

A thiolate-bridged diiron carbonyl complex derived from benzothiophene, [Fe2(μ-SC6H4CHCH)(CO)6], reacted with terminal alkynes HCCR (R = SiMe3, Ph, isobutyl) under photoirradiation conditions to afford diiron complexes with a 2,4-pentadienoyl moiety, [Fe2{μ-SC6H4(CH)3C(R)CO}(CO)5], via alkyne and CO insertion. In a similar reaction with N,N-dimethylpropargylamine, a diiron complex with a pentadienyl moiety, [Fe2{μ-SC6H4(CH)3C(NMe2)CH2}(CO)5], was obtained as an alkyne insertion product without CO insertion. This reaction involves 1,2-migration of a dimethylamino group. The corresponding reactions with alkyl propargyl ethers also produced diiron complexes containing pentadienyl moieties with an alkoxycarbonyl group via alkoxy migration with CO insertion. The migration process via C–N or C–O bond cleavage could be related to the coordination ability of N or O in the propargyl compounds.