The effect of the carbon ligand on the reaction of organozinc reagents in the synthesis of substituted 2,5-dihydrofurans: A rare example of an uncatalysed allylic-substitution reaction involving alkyl zinc halides

Organozinc halides derived from Grignard reagents behave differently in their reaction with ethyl (+/-)-(2RS,3SR)-tetrahydro-4-methylene-2-phenyl-3-(phenylsulfonoyl)furan-3-carboxylate (3) according to the hybridisation of the carbon Ligand. During the development of short multi-component reactions for the synthesis of diverse functionalized ethyl 2,5-dihydrofuran-3-carboxylates it was discovered that aryl and vinyl zinc halides undergo clean reaction with 3 in the presence of Pd(PPh3)(4). In contrast, when alkyl zinc halides are reacted with 3 in the presence of Pd(PPh3)(4), reductive desulfonation of 3 is observed. Remarkably, in the absence of a transition metal catalyst, the allylic substitution of 3 with alkyl zinc halides proceeds cleanly and in moderate to good yield.