Synthesis of 1,2‐diazepino[3,4‐ b ]quinoxalines and pyrido[3′,4′:9,8][1,5,6]oxadiazonino[3,4‐ b ]quinoxalines via a 1,3‐dipolar cycloaddition reaction

The reaction of 6‐chloro‐2‐(1‐methylhydrazino)quinoxaline 4‐oxide 8 with furfural, 3‐methyl‐2‐thiophene‐carbaldehyde, 2‐pyrrolecarbaldehyde, 4‐pyridinecarbaldehyde and pyridoxal hydrochloride gave 6‐chloro‐2‐[2‐(2‐furylmethylene)‐1‐methylhydrazino]quinoxaline 4‐oxide 5a , 6‐chloro‐2‐[1‐methyl‐2‐(3‐methyl‐2‐thienyl‐methylene)hydrazino]quinoxaline 4‐oxide 5b , 6‐chloro‐2‐[1‐methyl‐2‐(2‐pyrrolylmethylene)hydrazino]quinoxa‐line 4‐oxide 5c , 6‐chloro‐2‐[1‐methyl‐2‐(4‐pyridylmethylene)hydrazino]quinoxaline 4‐oxide 5d and 6‐chloro‐2‐[2‐(3‐hydroxy‐5‐hydroxymethyl‐2‐methyl‐4‐pyridylmethylene)‐1‐methylhydrazino]quinoxalme 4‐oxide 5e , respectively. The reaction of compound 5a or 5b with 2‐chloroacrylonitrile afforded 8‐chloro‐3‐(2‐furyl)‐4‐hydroxy‐1‐methyl‐2,3‐dihydro‐1 H ‐1,2‐diazepino[3,4‐ b ]quinoxaline‐5‐carbonitrile 6a or 8‐chloro‐4‐hydroxy‐1‐methyl‐3‐(3‐methyl‐2‐thienyl)‐2,3‐dihydro‐1 H ‐1,2‐diazepino[3,4‐ b ]quinoxaline‐5‐carbonitrile 6b , respectively, while the reaction of compound 5e with 2‐chloroacrylonitrile furnished 11‐chloro‐7,13‐dihydro‐4‐hydroxy‐methyl‐5,14‐methano‐1,7‐dimethyl‐16‐oxopyrido[3′,4′:9,8][1,5,6]oxadiazonino[3,4‐ b ]quinoxaline 7.