Diazomethane is yellow, toxic and reactive gas which is soluble in ether. Liquid diazomethane is explosive but may be handled safely in ethereal solution. It is prepared immediately prior to use and represented by the following resonance hybrid structures.

T. Sammakia, Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette, Ed., New York, 1995, 2 , 1512.

Major sources for the preparation of diazomethane are the basic hydrolysis of N -methyl- N -nitrosocompounds (Scheme 1-3).

Scheme 1

Scheme 2

Mechanism

The key step is base-catalyzed elimination.

Scheme 3