Reactions of novel trifluoromethyl propargylic carbocation with carbon nucleophiles
作者:Sung Lan Jeon、Joa Kyum Kim、Jang Bae Son、Bum Tae Kim、In Howa Jeong
DOI:10.1016/j.tetlet.2006.10.088
日期:2006.12
Trifluoromethyl propargylic carbocation [I] generated from the reaction of 1-amino substituted 3-trifluoromethyl-2-propynyl trimethylsilyl ether 1 with TMSOTf in CH2Cl2 at −15 °C, followed by warming to room temperature reacted with 1.2 equiv of substituted benzenes, RMgBr and allylsilane to give the enones 3a–l and 5, respectively. The reaction of [I] with anisole, followed by treatment with Grignard reagents
Cuts both ways: The title reaction consists of an addition/cyclization/dehydration sequence and affords the biologically important chiral 3,5‐diaryl‐5‐(trifluoromethyl)‐2‐isoxazolines 1 in excellent yields with high ee values. The flexibility of accessing either the S or R enantiomers of the products has been achieved by the appropriate choice of phase‐transfer catalyst (2).
A newly designed PE-supported arsine has been developed as an excellent catalyst for catalytic Wittig-type olefination. Simple ketones, in particular inactive ketones prove to be suitable substrates for the first time. This reaction provides an easy access to di-, tri-, and tetra-substituted olefins in high yield.
Efficient and Highly Enantioselective Construction of Trifluoromethylated Quaternary Stereogenic Centers via High-Pressure Mediated Organocatalytic Conjugate Addition of Nitromethane to β,β-Disubstituted Enones
A very effective high-pressure-induced acceleration of asymmetric organocatalyticconjugateaddition of nitromethane to sterically congested β,β-disubstituted β-CF3 enones has been developed. A combination of pressure (8–10 kbar) and noncovalent catalysis with low-loading of chiral tertiary amine-thioureas (0.5–3 mol %) is shown to provide very efficient access to a wide range of γ-nitroketones containing