Environmentally benign synthesis of methyl ketones is demonstrated via unprecedented bismuth­(III)-catalyzed activation and Markovnikov-type hydration of terminal acetylenes. Besides a batch process operating under reasonably mild conditions, a chemically intensified high-temperature continuous-flow methodology has also been developed using a coil reactor. The preparative capabilities of the flow process were demonstrated with multigram-scale alkyne hydrations. The methods presented rely on readily available bismuth­(III) salts as “green” catalysts and exhibit less environmental concerns than earlier methods.

Bismuth subnitrate is reported herein as a simple and efficient catalyst for the atom-economical synthesis of methyl ketones via Markovnikov-type alkyne hydration. Besides an effective batch process under reasonably mild conditions, a chemically intensified continuous flow protocol was also developed in a packed-bed system. The applicability of the methodologies was demonstrated through hydration of a diverse set of terminal acetylenes. By simply switching the reaction medium from methanol to methanol-d4, valuable trideuteromethyl ketones were also prepared. Due to the ready availability and nontoxicity of the heterogeneous catalyst, which eliminated the need for any special additives and/or harmful reagents, the presented processes display significant advances in terms of practicality and sustainability.