Abstract

Novel Conditions for the Preparation of Diazo Reagents in Flow and their Applications

Andre Charette, Professor, Universite De Montreal

Diazo reagents have been used extensively in organic synthesis. For example, they have been used in carbene chemistry (cyclopropanation, CH insertion reactions), in ylide formation, in cycloaddition chemistry and well as in Woff rearrangement and related reactions. Possible drawbacks of using diazo reagents are their potential instability, their tedious preparation involving sensitive intermediates and the high temperature involved for their formation. This presentation will highlight a new method for the preparation of aryl-substituted diazomethane derivatives in continuous flow using cheap and readily available reagents. Furthermore, the solutions of the diazo reagents that are produced are free from by-products that could prevent or inhibit a subsequent sensitive reaction. Examples of oxygen-, water and Lewis base sensitive reactions using the procedure will be shown. In addition, the reagents have been used in Lewis acid catalyzed processes. A large variety of structurally diverse diazo reagents have been prepared in high yields using this simple procedure. The second part of the talk will address the preparation of diazo reagents that bear two electron-withdrawing substituents. Although both methods are fundamentally different, they are submitted to the same limitations.