Asymmetric Synthesis of α-Substituted Aldehydes by Pd-Catalyzed Asymmetric Allylic Alkylation-Alkene Isomerization-Claisen Rearrangement

摘要

Enantiospecific aliphatic Claisen rearrangement was realized with generally high chirality transfer. The requisite substrates were synthesized via Pd-catalyzed asymmetric allylic alkylation (AAA) from easily obtained starting materials. After protection, the resultant bisallyl ethers underwent olefin isomerization and in situ Claisen rearrangement (ICR) to generate α-chiral aldehydes. Remarkable chemoselectivity in the olefin isomerization step was observed. An asymmetric synthesis of communiol A was accomplished applying this methodology.