Enantioenriched η 3 -Benzyl Palladium-Mediated Synthesis of Chiral Indanones: An Enantioselective 1,1-Carbene Migratory Insertion/Carbopalladation strategy at Room Temperature Using N-Tosylhydrazones as Carbene Source

N-Tosylhydrazones have served as a reliable carbene source in a wide range of carbene cross-coupling reactions over the last two decades. Yet, enantioselective processes involving N-Tosylhydrazones as carbene source are quite rare owing to the high temperature required to generate the carbenes. The in-situ generated diazo compound from N-Tosylhydrazones can interact with a metal center bearing a coupling partner to form a metal carbene complex or metallocarbene. The metal-carbene complex in a chiral environment can undergo an enantioselective 1,1-migratory insertion to generate a chiral metal complex. In such an environment, N-Tosylhydrazones bearing an aryl group can form an enantioenriched aromaticitydisrupted unstable η 3-benzyl Pd species via an enantioselective 1,1carbene migratory insertion. Herein, we report the development a 1,1carbene migratory insertion/carbopalladation cascade wherein the insitu generated enantioenriched unstable η 3-benzyl Pd species is trapped by an intramolecular olefin to access chiral indanone scaffolds at room temperature in yields up to 94% and e.r. up to 96:4. The methodology is unique in the generation of carbenes from N-Tosylhydrazones at room temperature and tolerance for diverse functional groups with catalyst loading as low as 3 mol% and ligand loading of 9 mol%. Surprisingly, the catalytic system is found to exhibit asymmetric amplification, giving an insight in to the structure of the active catalytic species and the catalytic cycle involved. Also, a photokinetic study of the isomerization of the pendant alkene in the synthesized indanone core is reported.