Isomerization and 1,3-dipolar cycloaddition of gem-difluorinated NH-azomethine ylides in the reaction of difluorocarbene with diarylmethanimines
作者:M. S. Novikov、A. F. Khlebnikov、K. A. Khistyaev、I. Magull
DOI:10.1007/s11172-008-0136-2
日期:2008.5
proceeds regioselectively with the formation of 4-fluoro-2,5-dihydrooxazoles. According to the quantum-chemical calculations by the DFT B3LYP/6-31G* method, 1,3-dipolar cycloaddition of difluorinated NH-azomethine ylides to a C=O bond with the formation of 4-fluoro derivatives of oxazole has lower barrier of activation than the reaction, leading to another regioisomer; the formal 1,2-H shift in the ylide
二氟卡宾与二芳基甲亚胺的反应导致形成 gem-difluorinated NH-azomethine 叶立德,发现两种类型的竞争转化具有特征:正式的 1,2-H 转变为 N-(二氟甲基)亚胺和 1,3 -偶极环加成到缺电子的多重键。α,α,α-三氟苯乙酮是二氟 NH-叶立德的有效偶极陷阱,将其添加到偶极子中会区域选择性地形成 4-氟-2,5-二氢恶唑。根据 DFT B3LYP/6-31G* 方法的量子化学计算,二氟化 NH-偶氮甲碱叶立德的 1,3-偶极环加成与 C=O 键形成 4-氟衍生物恶唑具有较低的势垒活化比反应,导致另一种区域异构体;正式的 1,