One‐Pot Sequential Four‐Component Reaction for the Synthesis of Novel Dihydro Oxaphospholo Pyrazole 2‐Oxides in Acetic Acid Medium

ABSTRACT A four‐component one‐pot sequential approach to five‐membered oxaphosphaheterocycles have developed. The method involves in situ generation of methylpyrazolin‐5‐one from ethyl acetoacetate and phenyl hydrazine. Further, a sequential reaction of methylpyrazolin‐5‐one with various aromatic aldehydes and phenyl dichloro phosphine afforded dihydro oxaphospholo pyrazole 2‐oxide derivatives.