Pd‐Catalyzed Decarboxylative Asymmetric Protonation of Sterically Hindered α‐Aryl Lactones and Dihydrocoumarins

• DOI: 10.1002/adsc.201800724
• Publication Date: 2018-06-23T04:10:42Z
• Authors: Jinju James; Ramulu Akula; Patrick J. Guiry
• Keywords: Asymmetric induction

Abstract Pd‐catalyzed decarboxylative asymmetric protonation (DAP) has been developed for sterically hindered α‐aryl lactone and dihydrocoumarin substrates. Optimization studies were conducted using δ‐lactone‐ dihydrocoumarin‐derived α‐aryl, β‐oxo‐allyl esters with 2,4,6‐trimethoxyphenyl as the aryl substituent. In absence of a chiral P,N‐ ligand, (1 R ,2 S ) ‐ (−)ephedrine, cheap readily available proton donor, induced enantioselectivities up to 92% ee 88% substrates, respectively. Bulky groups containing di‐ ortho substitutions naphthyl gave highest 86%, A stereochemical rationale is proposed explain preferred sense induction. magnified image