Synthesis of fully substituted pyrazoles from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides <i>via</i> a [[3 + 3] − 1] pathway
Bin Cheng, Bian Bao, Wei Xu, Yuntong Li, Hui Li, Xin‐Ping Zhang, Yun Li, Taimin Wang, Hongbin Zhai
Abstract
A novel and practical protocol for the synthesis of fully substituted pyrazoles from pyridinium 1,4-zwitterionic thiolates and hydrazonoyl chlorides in excellent yields under mild conditions is described. The transformation proceeds via an unusual [[3 + 3] - 1] pathway, which involves a formal [3 + 3] cascade cyclization followed by a spontaneous ring-contraction/sulfur extrusion reaction from 4H-1,3,4-thiadiazine intermediates.
Topics & Concepts
PyridiniumChemistryCascadeRing (chemistry)Medicinal chemistryContraction (grammar)Combinatorial chemistrySulfurStereochemistryOrganic chemistryInternal medicineChromatographyMedicineSulfur-Based Synthesis TechniquesCatalytic C–H Functionalization MethodsCyclopropane Reaction Mechanisms