cyclopropanation of alkenes; condensation with organoboranes; 1,3-dipolar cycloaddition with alkynes, yielding substituted pyrazoles.
Diazoacetaldehyde is not commercially available but can be prepared from β-N-methylanilinoacrolein and p-Toluenesulfonyl Azide. A simple and convenient preparation involves treating Acetic Formic Anhydride with Diazomethane in diethyl ether.
Extreme caution must be exercised when handling diazoacetaldehyde. It is thermally unstable and will detonate violently if overheated (do not expose to temperatures above 50 °C), emitting toxic fumes of NOx. At low temperatures, diazoacetaldehyde can be stored for several weeks without noticeable decomposition. This reagent should only be handled in a fume hood.
