Mechanistic insights into the Pt(II)-catalyzed rearrangements from homopropargylic alcohols to furans: Hydrogen vs tert-butyldimethylsilyl group migrations

By carrying out B3LYP calculations, we have performed a detailed mechanism study on the reaction of platinum catalyzed rearrangements of homopropargylic alcohols derivatives into isomeric polysubstituted furans in THF and toluene solutions, respectively. The reaction steps include α,β-unsaturated carbene complex formation, and H atom or Si (Si = tert-butyldimethylsilyl) group migration. In the step of α,β-unsaturated carbene complex formation, the methoxy group is the optimal leaving group. Our calculations are consistent with the experimental results that Si-migration is favored in toluene while H-migration is favored in THF. Based on the Cl-aided H-migration mechanism postulated by Ferreira et al., we proposed a H2O and Cl co-aided H-migration mechanism in THF, in which H2O and Cl both act as the medium to transfer H.