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Continuous‐Flow N‐Heterocyclic Carbene Generation and Organocatalysis
Author(s) -
Di Marco Lorenzo,
Hans Morgan,
Delaude Lionel,
Monbaliu JeanChristophe M.
Publication year - 2016
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.201505135
Subject(s) - carbene , organocatalysis , chemistry , transesterification , nucleophile , organic base , homogeneous catalysis , organic chemistry , combinatorial chemistry , catalysis , michael reaction , base (topology) , vinyl acetate , enantioselective synthesis , polymer , mathematical analysis , mathematics , copolymer
Two methods were assessed for the generation of common N‐heterocyclic carbenes (NHCs) from stable imidazol(in)ium precursors using convenient and straightforward continuous‐flow setups with either a heterogeneous inorganic base (Cs 2 CO 3 or K 3 PO 4 ) or a homogeneous organic base (KN(SiMe 3 ) 2 ). In‐line quenching with carbon disulfide revealed that the homogeneous strategy was most efficient for the preparation of a small library of NHCs. The generation of free nucleophilic carbenes was next telescoped with two benchmark NHC‐catalyzed reactions; namely, the transesterification of vinyl acetate with benzyl alcohol and the amidation of N ‐Boc‐glycine methyl ester with ethanolamine. Both organocatalytic transformations proceeded with total conversion and excellent yields were achieved after extraction, showcasing the first examples of continuous‐flow organocatalysis with NHCs.