A novel approach to chemoselective synthesis of biologically important CF3 -subsituted pyrazolines was developed via a Lewis base catalyzed intermolecular triazene cycloaddition reaction of an array of terminal/internal alkenes with CF3 CHN2 . This strategy features a catalytic amount of 1,8-diazabicyclo[5.4.0]undec-7-ene, high yields (up to 95 %), wide substrate scope and excellent functional group tolerance (54 examples). Importantly, we preformed scaffold diversification of a panel of known pharmaceuticals, natural products, and bioactive heterocycles to generate the corresponding pyrazoline derivatives with potential broad bioactivities for further development.
Keywords: 2,2,2-trifluorodiazoethane; Lewis base catalysis; cycloaddition reactions; pyrazolines; trifluoromethyl group.
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