Diazomethane is among the most versatile and useful reagents for introducing methyl or methylene groups into organic compounds. However, its conventional generation and purification by distillation involve a certain safety risk because of its explosive nature. In addition, diazomethane is a potent carcinogen and extremely poisonous. To circumvent handling and storage of such hazardous reagents, they are best produced in-situ on-demand from benign precursors directly at the site of use. In continuous-flow processing, safety is one of the most significant advantages over a traditional batch set-up, therefore it is the ideal technique for the generation of hazardous species. We demonstrated the in-situ generation of anhydrous diazomethane in continuous flow systems. Key to this strategy was the use of membrane separation technology. Diazomethane is generated from solutions of Diazald and KOH and the semi-permeable membrane selectively allows pure diazomethane gas to diffuse which is then instantly consumed by the substrate. Two different strategies can be applied: a fully continuous tube-in-tube and a configurationally more simple and flexible tube-in-flask reactor. Both approaches allow the on-demand generation of anhydrous diazomethane without dangerous and laborious purification operations or any exposure of the operator. Both reactor concepts will be presented, including their application to diverse chemistries.

In-situ on-demand production of anhydrous diazomethane using membrane separation technology

255th National Meeting (2018)

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