Microwave-activated synthesis of thiazolo[5,4-d]thiazoles by a condensation/oxidation sequence

A microwave-assisted prepn. of sym. thiazolo[5,4-d]thiazoles from the corresponding aldehydes is presented. The two-step reaction sequence comprises the condensation of aldehydes with dithiooxamide followed by oxidn./aromatization with 1,4-benzoquinone derivs. The new procedure provides the desired products in good yields and in most cases allows redn. of the excess of aldehyde employed in the process compared to previous methodologies. For the first time, application of the reaction both on arom. and aliph. aldehydes is demonstrated.