Iodobenzene-Catalyzed Synthesis of Fully Functionalized NH-Pyrazoles and Isoxazoles from α,β-Unsaturated Hydrazones and Oximes via 1,2-Aryl Shift
Vikram Singh, Deepak Kumar, Bal Krishna Mishra, Bhoopendra Tiwari
Abstract
An iodine(III)-catalyzed general method for the synthesis of fully functionalized NH-pyrazoles and isoxazoles from α,β-unsaturated hydrazones and oximes, respectively, via cyclization/1,2-aryl shift/aromatization/detosylation, has been developed. The reaction progresses through an anti -Baldwin 5- endo - trig cyclization. It gives direct access to an advanced intermediate for the preparation of valdecoxib and parecoxib, drugs used for COX-inhibition. In addition, a method for N -alkynylation of pyrazoles has also been developed in the presence of TIPS-EBX.
Topics & Concepts
ChemistryArylIodobenzeneCatalysisAromatizationAcetanilidePyrazoleIodineCombinatorial chemistryIsoxazoleMedicinal chemistryOrganic chemistryAlkylClick Chemistry and ApplicationsSynthesis and Catalytic ReactionsSynthesis and Characterization of Pyrroles