An efficient synthesis of novel 1,3-oxazolo[4,5-d]pyridazinones

A convenient and versatile synthetic approach to substituted 1,3-oxazolo[4,5-d]pyridazinones is developed. The oxazole ring was formed upon reaction of 5-amino-4-hydroxy-3(2H)-pyridazinone with various carboxylic acid derivatives using a microwave-assisted procedure, which favors the reaction time and purity of the resulting products. The developed methodology is suitable for rapid, parallel, automated synthesis of oxazolopyridazinone libraries.