Asymmetric Synthesis of Fluorinated Allenes by Rhodium‐Catalyzed Enantioselective Alkylation/Defluorination of Propargyl Difluorides with Alkylzincs. (16th August 2021)

• Record Type: Journal Article
• Authors: Ng, Jia Sheng; Hayashi, Tamio
• Is Part Of: Angewandte Chemie. Volume 133:Number 38(2021)
• Page Start: 20939
• Page End: 20943
• Publication Date: 2021-08-16
• Subjects: asymmetric defluorination -- axially chiral allenes -- chiral diene ligands -- enantioselectivity -- rhodium; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202109290
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: The reaction of propargyl difluorides R 1 CF2 C≡CR 2 with alkylzincs R 3 ZnCl giving axially chiral fluorinated allenes R 1 FC=C=CR 2 R 3 with high enantioselectivity (up to 99 % ee ) was found to be catalyzed by a chiral diene/rhodium complex. A key step in the catalytic cycle is selective elimination of one of the enantiotopic fluorides at the β‐position of an alkenyl‐Rh intermediate, which is generated by regioselective addition of R 3 ‐Rh onto the triple bond of the starting difluorides. Abstract : The reaction of propargyl difluorides, R 1 CF2 C≡CR 2, with alkylzincs, R 3 ZnCl, giving axially chiral fluorinated allenes, R 1 FC=C=CR 2 R 3, with high enantioselectivity (up to 99 % ee ) was found to be catalyzed by a chiral diene/rhodium complex. A key step in the catalytic cycle is selective elimination of one of the enantiotopic fluorides at the β‐position of an alkenyl‐Rh intermediate, which is generated by regioselective addition of R 3 ‐Rh onto the triple bond of the starting difluorides.