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Highly Selective β ‐Hydride Elimination in the Pd‐Catalyzed Cross‐Coupling of N ‐Tosylhydrazones with Benzyl Bromides
Author(s) -
Sun Zhenze,
Du Chaoqun,
Liu Ping,
Wei Yu,
Xu Liang,
Dai Bin
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201702521
Subject(s) - chemistry , migratory insertion , carbene , palladium , regioselectivity , olefin fiber , catalysis , hydride , coupling reaction , combinatorial chemistry , medicinal chemistry , photochemistry , hydrogen , organic chemistry
In Pd‐catalyzed cross‐coupling reactions between tosylhydrazones and organohalides, the competitive β –H elimination of palladium complex intermediate generated through palladium‐carbene complex's migratory insertion is usually avoided by combining two specific coupling partners, in which only one contains a β ‐H. To address this limitation, herein we present cross‐coupling reactions between benzyl bromides and tosylhydrazones derived from benzocyclic ketones. Benzyl‐substituted dihydronaphthalenes and 1 H ‐indenes can be obtained in up to 88% yields and 25:1 selectivity for the cyclic olefin via this method. DFT studies were performed to elucidate the reaction mechanism. The β ‐H elimination process, which follows the migratory insertion of Pd carbene intermediates, favours the abstraction of hydrogen atoms on the cyclic skeletons and results in the observed regioselectivity.