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Palladium–N‐Heterocyclic Carbene (NHC)‐Catalyzed Asymmetric Synthesis of Indolines through Regiodivergent C(sp 3 )H Activation: Scope and DFT Study
Author(s) -
Katayev Dmitry,
Larionov Evgeny,
Nakanishi Masafumi,
Besnard Céline,
Kündig E. Peter
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403985
Subject(s) - enantiopure drug , palladium , carbene , chemistry , catalysis , denticity , chirality (physics) , enantioselective synthesis , methylene , stereochemistry , medicinal chemistry , combinatorial chemistry , organic chemistry , crystal structure , physics , nambu–jona lasinio model , chiral symmetry breaking , quantum mechanics , quark
Abstract Two bulky, chiral, monodentate N‐heterocyclic carbene ligands were applied to palladium‐catalyzed asymmetric CH arylation to incorporate C(sp 3 )H bond activation. Racemic mixtures of the carbamate starting materials underwent regiodivergent reactions to afford different trans ‐2,3‐substituted indolines. Although this C Ar C alkyl coupling requires high temperatures (140–160 °C), chiral induction is high. This regiodivergent reaction, when carried out with enantiopure starting materials, can lead to single structurally different enantiopure products, depending on the catalyst chirality. The CH activation at a tertiary center was realized only in the case of a cyclopropyl group. No CH activation takes place alpha to a tertiary center. A detailed DFT study is included and analyses of methyl versus methylene versus methine CH activation is used to rationalize experimentally observed regio‐ and enantioselectivities.