Intramolecular Nitrone Cycloaddition of α-(Trifluoromethyl)styrenes. Role of the CF<sub>3</sub> Group in the Regioselectivity
作者:Fernando Rabasa-Alcañiz、Amparo Asensio、María Sánchez-Roselló、Marcos Escolano、Carlos del Pozo、Santos Fustero
DOI:10.1021/acs.joc.6b02880
日期:2017.3.3
The intramolecular 1,3-dipolar cycloaddition of ortho-substituted 1,1,1-trifluoromethylstyrene-derived nitrones is described. Tricyclic fused isoxazolidines were obtained as major or exclusive products, in contrast to the case for nonfluorinated substrates, which rendered the bridged derivatives. This change in the regioselectivity was attributed to the electronic and, particularly, steric requirements
描述了邻位取代的1,1,1-三氟甲基苯乙烯衍生的硝酮的分子内1,3-偶极环加成。与非氟化底物的情况相反,三环稠合的异恶唑烷作为主要或排他性产物获得,非氟化底物形成桥连衍生物。区域选择性的这种变化归因于三氟甲基与甲基相比的电子要求,尤其是空间要求。值得一提的是,三氟甲基苯乙烯首次在1,3-双极性分子内环加成反应中用作亲双性油,从而导致相应的带有季三氟甲基部分的异恶唑烷。最后,