β‐Quaternary α‐Amino Acids via Iridium‐Catalyzed Branched and Enantioselective Hydroalkylation of 1,1‐Disubstituted Styrenes

Abstract A cationic Ir(I)‐complex modified with the chiral diphosphine DM‐SEGPHOS mediates the hydroalkylation of diverse α‐methyl styrenes with N‐aryl glycine derivatives. The processes occur with complete branched selectivity and high enantioselectivity. Styrenes possessing higher α‐alkyl substituents also participate to provide the targets with moderate to excellent levels of diastereoselectivity. The products are readily advanced to β‐quaternary α‐amino acids that are inaccessible or cumbersome to access by other means. In broader terms, the study demonstrates how catalyst controlled C─H additions across alkenes can be used to execute the by‐product‐free construction of contiguous acyclic trisubstituted and quaternary centers.