Borane catalyzed selective diazo cross-coupling towards pyrazoles
Decomposition of donor-acceptor diazo compounds leads to the formation of reactive carbene intermediates. These can undergo a wide variety of carbene transfer reactions to yield synthetically useful products. Herein, we report a selective borane catalyzed cyclization reaction from the combination of two different diazo compounds to afford N-substituted pyrazoles. The selective decomposition of the more reactive α-aryl α-diazoester and subsequent reaction with a vinyl diazoacetate produces N-alkylated pyrazoles in a regioselective manner. Catalytic amounts of tris(pentafluorophenyl)borane (10 mol%) were employed to afford the pyrazole products (36 examples) in yields from 59 to 80%. Extensive DFT studies have been undertaken to interpret the mechanism for this reaction which was found to go through two tandem catalytic cycles, both catalyzed by B(C6F5)3.
Australian Research Council
University of Wollongong
Publication titleAdvanced Synthesis and Catalysis
Department/SchoolRecruitment and International
PublisherWiley-V C H Verlag Gmbh
Place of publicationPo Box 10 11 61, Weinheim, Germany, D-69451
Rights statement2021 The Authors. Advanced Synthesis & Catalysis published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, (https://creativecommons.org/licenses/by/4.0/) which permits use, distribution and reproduction in any medium, provided the original work is properly cited.