Synthesis of hydrogenated indazole derivatives starting with α,β-unsaturated ketones and hydrazine derivatives

The reaction of hydrazine derivatives with alpha,beta-unsaturated ketones, such as cyclohexenyl(phenyl) methanone and (E)-2-benzylidenecyclohexanone, were investigated. The reaction between methylhydrazine and e.g., cyclohexenyl(phenyl)methanone was particularly interesting as 3a,4,5,6,7,7a-hexahydro-1-methyl-3-phenyl-1H-indazole was obtained as the major product together with 4,5,6,7-tetrahydro-2-methyl-3-phenyl-2H-indazole as a minor product. (C) 2009 Elsevier Ltd. All rights reserved.