Abstract :
[en] 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 (Cs2CO3 or K3PO4) or a homoge¬neous organic base (KN(SiMe3)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 transfor¬ma¬tions proceeded with total conversion and excellent yields were achieved after extraction, showcasing the first examples of continuous-flow organocatalysis with NHCs.
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