A novel and practical method for the synthesis of 3,5‐bis(trifluoromethyl)‐4,5‐dihydro‐1H‐pyrazoles by [3+2] cycloaddition reactions of α‐(trifluoromethyl)styrenes with 2,2,2‐trifluorodiazoethane (CF₃CHN₂) has been developed. The cyclization reaction proceeds smoothly in the presence of a catalytic amount of Et₃N, affording a variety of bis(trifluoromethyl)‐substituted 2‐pyrazolines in good to excellent yields. This method also exhibits a broad substrate scope and tolerates various functional groups.

中文翻译：

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Et3N催化的α-（三氟甲基）苯乙烯与2,2,2-三氟重氮乙烷的环加成反应获得双（三氟甲基）取代的吡唑啉

通过α-（三氟甲基）苯乙烯与2,2,2-的[3 + 2]环加成反应合成3,5-双（三氟甲基）-4,5-二氢-1H-吡唑的新颖实用方法已经开发出三氟重氮乙烷（CF ₃ CHN ₂）。在催化量的Et ₃ N的存在下，环化反应平稳进行，从而提供了多种双（三氟甲基）取代的2-吡唑啉，收率高至优异。该方法还表现出广泛的底物范围，并能耐受各种官能团。