Synthesis of γ-Keto-δ-alkenyl-phosphonates and Phosphine Oxides as Precursors of Novel Phosphono-pyrazoline and pyrazole Derivatives
摘要:
Herein we report the synthesis of gamma-keto-delta-alkenyl-phosphonates and phosphine oxides by two versions of strategy (a) which involves the addition of dialkyl phosphites to alpha,alpha'-diarylideneketones, and by strategy (b) which utilizes the reaction of P-chlorodiphenylphosphine with diarylidene ketones in acetic acid. On reaction with hydrazine derivatives, gamma-keto-delta-alkenyl-phosphonates and phosphine oxides give 3-phosphonoethylpyrazoline derivatives which can be converted into the corresponding aromatic pyrazoles by oxidative dehydrogenation, using sodium nitrite as oxidizing agent.