An efficient strategy for the general synthesis of 3-aryl substituted pyrazolo[5,1-c][1,4]benzoxazines and pyrazolo[1,5-a][1,4]benzodiazepin-6(4H)-ones

An efficient strategy for the general synthesis of 3-aryl substituted pyrazolo5,1-c]1,4]benzoxazines and pyrazolo1,5-a]1,4]benzodiazepin-6(4H)-ones has been developed using intramolecular 1,3-dipolar cycloaddition. The hydrazonoyl chloride, the precursor of the cycloadduct, is accessed easily through a two-step reaction carried out in one-pot. It is then used without purification for the base induced formation of the nitrilimine, which undergoes subsequent in situ intramolecular cycloaddition with an alkyne to afford the desired product. The reaction protocol has also been applied in bis-heteroannulation and in the synthesis of uracil derivatives of biological interest. The operational simplicity of the process, the use of cheap starting materials, and the relatively short reaction times required make the process convenient and practical.