According to previous reports on ph

According to previous reports on phosphoramidite ligands prompted palladium-catalyzed transformation and the reaction details in our experiments:27,12c a possible mechanism for the stereochemistry was depicted as Scheme 1. The stereochemical outcome of this transformation can be rationalized by consideration of the geometry of the palladium-mediated homo-TMM intermediate. Considering the good selectivity and the special example of 3d, the structure of the key intermediate is presumably described as Int-A. The enolate oxygen is likely binding to the palladium cation center, giving a formal 6-membered ring system and geometry confirmed enolate. The Si face of the ring was presumably blocked effectively by the phosphoramidite ligand, and the acceptor 2a would access the Inter-A from the Re face. To minimize the interactions between the diphenyl iminyl group and the ligated ligand, Int-B is favored to afford 3g as the major product; this inference potentially explains the decrease in the diastereose lectivity ratio for 8f and 8h. The thermodynamic trans cyclization and the regioselective ring closure (C1 vs C2) process indicate that this intermolecular cycloaddition is a stepwise process.