Highly Efficient Synthesis of Chiral α-CF<sub>3</sub> Amines via Rh-Catalyzed Asymmetric Hydrogenation
作者:Jun Jiang、Wenxin Lu、Hui Lv、Xumu Zhang
DOI:10.1021/acs.orglett.5b00087
日期:2015.3.6
Highly enantioselective catalyticasymmetrichydrogenation of α-CF3-enamides has been achieved by employing rhodium–DuanPhos as the catalyst, which provides a readily accessible method for the synthesis of chiral trifluoromethylated amines. The reaction has a broad substrate scope; both aryl- and alkyl-substituted α-CF3-enamides worked smoothly and afford the corresponding chiral amines in high yields
Nouvelle synthese de trifluoromethylcetones et d' /ga-bromo trifluoromethylcetones
作者:J.P. Begue、D. Mesureur
DOI:10.1016/s0022-1139(00)82782-7
日期:1988.5
We report a new method for the preparation of trifluoromethylketones, as an alternative to the use of organometallics. The condensation of phosphoniumylides with trimethylsilyl trifluoroacetate provides silyloxy enol ethers whose hydrolysis leads to trifluoromethylketones. Bromation of the same silyloxy enol ether is also a convenient preparation of /ga-bromo trifluoromethylketone.
The spontaneous addition of 2-(trimethylsilyl)thiazole (2-TST, 1) to various alkyl and aryl perfluoroalkyl ketones 2 in THF at 80°C affords the corresponding tertiary alcohols 4 which by thiazolyl-to-formyl conversion are transformed into fluorinated α-hydroxy aldehydes 6. The formation of silyl enol ether side products is observed in the reaction of 2-TST 1 with alkyl ketones 2b-e.
Despite the very low acidity of the inert α C−H bonds (pKa≈42.6), directasymmetric α-C(sp3)−H addition of N-unprotected propargylic amines to trifluoromethyl ketones has been achieved by using a chiral pyridoxal as the carbonyl catalyst, producing a broad variety of chiral alkynyl β-aminoalcohols in high yields with excellent stereoselectivities (up to 84 % yield, >20 : 1 dr, 99 % ee).
尽管惰性 α C−H 键的酸度非常低 (p K a ≈ 42.6),但通过使用手性吡哆醛,已经实现了 N-未保护的炔丙胺与三氟甲基酮的直接不对称 α-C( sp 3 )−H 加成作为羰基催化剂,以高产率和出色的立体选择性(高达 84% 产率,>20:1 dr,99% ee)生产多种手性炔基 β-氨基醇。