January 2022

Spirocyclic 3,5-difluorocyclohexa-2,5-dienones possessing a triisopropylsiloxy-containing cyclic ether appendage were synthesized by oxidative dearomatization of the corresponding phenols. By group selectivity in the nucleophilic 1,4-addition/elimination reaction, highly stereoselective formation of the spiro center was successfully achieved. This reaction might provide access to total syntheses of (+)-bisdechlorogeodin and (+)-geodin with complete control of the formation of the spirocyclic structure.

A copper-catalyzed radical difluoroalkylation of arylacetylenes with bromodifluoroamides has been developed. The reaction exhibits good functional group tolerance and allows access to a variety of substituted α-alkynyl-α,α-difluoroacetamides in moderate to good yields. The potential for scale-up reaction and products derivatization also makes this method attractive for practical applications. Preliminary mechanistic studies suggest that a radical reaction pathway might be involved in the catalytic system.

The Thorpe–Ingold effect was applied to the design of a chiral ligand of π–copper(II) catalysts for the enantioselective α-fluorination of N-acyl-3,5-dimethylpyrazoles, and also for the enantioselective Mukaiyama–Michael, Diels–Alder, and 1,3-dipolar cycloaddition reactions of N-acryloyl-3,5-dimethylpyrazoles. The use of β,β-dimethyl-β-arylalanine-type ligand gave desired products with higher enantioselectivity compared to with previously reported β-arylalanine-type ligands.