Exalted Resonance Demands in the Substituent Effects on the Acetolyses of 2-Arylethyl Trifluoromethanesulfonates Destabilized by CN and CF<sub>3</sub>Groups
Substituent effects on the acetolysis rates of 2-aryl-1-cyano-1-(trifluoromethyl)ethyl trifluoromethanesulfonates (α-OTf) and 2-aryl-2-cyano-2-(trifluoromethyl)ethyl trifluoromethanesulfonates (β-OTf) were investigated by using LArSR equation. The obtained ρ and r+ values were ρ = −3.28, r+ = 0.98 and ρ = −3.48, r+ = 0.93 for the acetolysis of α-OTf and β-OTf, respectively. The obtained ρ values are comparable to those for typical aryl-assisted solvolyses, but the r+ values are much larger. The large r+ values suggest that the ester bond cleavages in the deactivated aryl-assisted solvolyses are assisted by the strong participation of the β-aryl group.
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.
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