Facile strategy for the preparation of pyrazoline derivatives through phosphine-promoted [2 + 3] cycloaddition of dialkyl azodicarboxylates with β,γ-unsaturated α-keto esters

ABSTRACTA facile phosphine-promoted [2 + 3] cycloaddition of dialkyl azodicarboxylates with β,γ-unsaturated α-keto esters was developed, and a series of pyrazoline derivatives were obtained with good yields under mild conditions. Furthermore, the scope of the cyclizations was investigated.