Suzuki coupling for preparation of allenes - ligand effects and chirality transfer

A general and efficient palladium-catalyzed coupling of propargylic carbonates with organoboronic acids has been developed by identifying a commercially available semi-labile bidentated o-(diphenylphosphino) benzaldehyde as the effective ligand affording allenes under a set of very mild reaction conditions. Many functional groups are tolerated in this reaction, and high chirality transfer has also been realized in the presence of water leading to a very rapid reaction for the synthesis of easily racemized 1,3-diarylallenes. A rationale has been proposed to demonstrate the role of the ligand.