Reactions of an imidazo[4,5-c]isoxazole-6-carboxylate with dimethyl acetylenedicarboxylate; formation of the first example of a [1,4]diazepino[2,3-c]isoxazole

The synthesis of the first example of a [1,4]diazepino[2,3-c]isoxazole deri vative is reported. Reaction of an imidazo[4,5-c]isoxazole with acetylenic esters has been shown to lead to the formation of 2-pyrrol-2-yl imidazoles, Here we report an alter-native reaction pathway in which the fused imidazo le ring adds a molecule of acetylenic eater, and undergoes ring expansion t o a fused El, il]diazepine. A mechanism for the reaction is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.