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

A microwave-assisted preparation of symmetrical 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 oxidation/aromatization with 1,4-benzoquinone derivatives. The new procedure provides the desired products in good yields and in most cases allows reduction of the excess of aldehyde employed in the process compared to previous methodologies. For the first time, application of the reaction both on aromatic and aliphatic aldehydes is demonstrated.