Preparation of Alkyl 4,5-Dihydro-2H-benz[g]indazole-2-carboxylates and Methyl 4,5-Dihydro-2H-benz[e]indazole-2-carboxylates from Dilithiated 1-Tetralone or 2-Tetralone Carboalkoxyhydrazones and Aromatic Esters

Dilithiated 1-tetralone or 2-tetralone carboalkoxyhydrazones were prepared in excess lithium diisopropylamide and condensed with a variety of aromatic esters followed by acid cyclization of C-acylated intermediates to give substituted dihydrobenzindazoles, alkyl 4,5-dihydro-2H-benz[g]indazole-2-carboxylates and methyl 4,5-dihydro-2H-benz[e]indazole-2-carboxylates. These fused-ring heterocyclic products have considerable application potential.