Promotion effects of Lewis acid/(CH3)4NI on [Co(CO)4]ˉ-catalyzed C–N bond activation in the carbonylation of trimethylamine

•Lewis acid and (CH3)4NI were used to promote carbonylation of trimethylamine.•High activity of NaCo(CO)4 was obtained under relatively mild reaction conditions.•Excellent selectivity and yield of N,N-dimethylacetamide were obtained.•The catalytic mechanism was proposed.

An effective synthesis of N,N-dimethylacetamide (DMAc) via NaCo(CO)4-catalyzed carbonylation of trimethylamine is reported. Lewis acid (AlCl3, FeCl3, BiCl3, InCl3 etc.) and (CH3)4NI were used as promoters to activate the unreactive sp3 carbon–nitrogen (C–N) bond of trimethylamine and a significant increase in catalytic activity was observed. High selectivity (98%) and yield of DMAc (96%) were obtained under relatively mild reaction conditions. Based on the role of promoters and the products in the reaction, a plausible mechanism that contains two different ways of activating C–N bond was proposed.

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