GaCl₃-Catalyzed Insertion of Diazene Derivatives into the Cyclopropane Ring¹

GaCl3 has been found to efficiently catalyze the formal cycloadditions of diazene derivatives 6 onto 2-arylcyclopropane-1,1-dicarboxylates 5, giving rise to the pyrazolidine derivatives 7. The insertion into the cyclopropane ring proceeds with complete regioselectivity to furnish 5-arylpyrazolidine-1,2,3,3-tetracarboxylates exclusively; however, the cis-configured azo compound N-phenyltriazolinedione gave the two possible regioisomeric pyrazolidine derivatives in ratios varying from 1:1.5 to 1:3. Conceivable mechanisms of these transformations are being discussed.研究发现，三氯化镓（GaCl₃）可高效催化重氮衍生物6与2-芳基环丙烷-1,1-二羧酸酯5之间的形式环加成反应，生成吡唑烷衍生物7。该反应对环丙烷环的插入过程具有完全的区域选择性，仅专一得到5-芳基吡唑烷-1,2,3,3-四羧酸酯；然而，顺式构型的偶氮化合物N-苯基三唑啉二酮则会生成两种区域异构的吡唑烷衍生物，其比例范围为1:1.5至1:3。本文对上述转化过程的可能反应机理进行了探讨。