Investigation of routes to indeno[2,1‐ f ] ‐2 H ‐1,2,4‐triazepinediones

The synthesis of a number of 3‐(substituted thiosemiearbazido)‐2‐(a]koxycarbonyl)indones (1) from 2‐alkoxycarbonyl‐1, 3‐indandiones and substituted thiosemicarbazides is described. Cyeliza‐tion of compounds 1 in the presence of a variety of catalysts gave substituted Δ 2 ‐1,2,4‐triazoline‐5‐thiones ( 3 ) and ( 4 ), instead of the expected substituted 3(4H)‐thioxoindeno[2,1‐ f ]‐2H‐1,2,4‐triazepine‐5(5aH),6‐diones (2). The preparation of 4‐(2‐methyl‐1,3‐dioxo‐2‐indanylmethyl)semi‐carbazide ( 9 ) is reported. Cyelization of 9 gave 5,5a‐dihydro‐5a‐methylindeno[2,1‐ f ]‐2H‐1,2,4‐triazepine‐3(4H),6‐dione ( 10 ). Structure assignments of these compounds are discussed.