Asymmetric Synthesis of Tri- and Tetrasubstituted Trifluoromethyl Dihydropyranones from α-Aroyloxyaldehydes via NHC Redox Catalysis
作者:Alyn T. Davies、Philip M. Pickett、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/cs500667g
日期:2014.8.1
The asymmetric synthesis of tri- and tetrasubstituted trifluoromethyl dihydropyranones via an NHC-catalyzed redox process, introducing methyl, benzyl, and aryl substituents to the C(5) position, is presented. Their substrate-controlled derivatization into delta-lactones and cyclic hemiacetals containing stereogenic trifluoromethyl groups is also described.
Synthesis of Chiral Fluorinated Hydrazines via Pd-Catalyzed Asymmetric Hydrogenation
An enantioselective hydrogenation of fluorinated hydrazones has been achieved by employing [Pd(R)-DTBM-SegPhos(OCOCF3)(2)] as the catalyst, providing a general and convenient method toward chiral fluorinated hydrazines. A broad substrate scope including beta-aryl-, gamma-aryl-, and alkyl-chain-substituted hydrazones worked efficiently in high yields and up to 94% of enantioselectivity. The reductive amination between trifluoromethyl-substituted ketones and benzohydrazides could also proceed smoothly.