The regiospecific synthesis of N ‐substituted pyrazoles. I. 1‐ and 2‐substituted indeno[1,2‐c]pyrazol‐4(1 H )‐ones

The reaction of the enaminoketones ( 2 or 5 ) of 2‐acyl‐1,3‐indandiones with unsymmetrical hydrazines results in the regiospecific synthesis of 1,3‐ or 2,3‐disubstituted indeno[1,2‐ c ]pyrazol‐4(1 H )‐ones ( 4 or 7 ). The synthesis of the enaminoketones ( 2 or 5 ) is accomplished by way of amine addition to the 2‐acyl‐1,3‐indandiones 8a‐c or by reduction of the indenoisoxazole 9 . The structural assignment of the isomeric indenopyrazoles 4 and 7 is based upon 1 H‐nmr chemical shifts.