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