Unprecedented Formation of Δ2‐Isoxazoline and/or 1‐Nitroso‐pyrazoline from α‐Bromoketone Oximes and Diazo Compounds.

Reaction of α-bromoketone oximes with diazo compounds in the presence of a metal catalyst and base led to the unprecedented formation of two types of rings: Δ 2 -isoxazolines and 1-nitrosopyrazolines.