C 1 -Symmetric Ligand-Enabled Stereoselective Formal [5+4] Cycloadditions of Palladium-Containing 1,5-Carbodipoles

The zwitterions bearing a π-allylmetal moiety, as highly reactive dipoles, have been employed for various asymmetric cycloadditions for the synthesis of diverse chiral carbo- and heterocycles. However, the reported all-carbon-based dipoles are generally limited to 1,3- or 1,4-type ones. Here, we disclose a new type of cyclic 1,5-carbodipoles, generated from the carbonates of 4-hydroxy-2-cyclopentenones under palladium catalysis via a deprotonation strategy, which can undergo highly asymmetric formal [5+4] cycloadditions with diverse 1-aza/oxadienes. New C1-symmetric bisphosphines containing two electronically and sterically different binding units or even hybrid phosphine/sulfonamide ligands from simple chiral sources are developed, which prove to be much superior to classical C2-symmetric ligands regarding the catalytic activity and stereoselectivity. Moreover, diastereodivergent catalysis could be realized for some substrate assemblies via ligand-control. Both 1,5-carbodipole species and chiral C1-symmetric ligands would find more application in asymmetric synthesis.