Synthesis of a New Diels-Alder Quinone Adduct and Its Use in Preparing Thiazolo- and Oxazoloquinolines

Syn (or anti) cinnamaldehydeoxime (la, b) undergoes Diels-Alder addition to tetrabromo-p-benzoquinone (2) in dry xylene in 1 : 1 and 2 : 1 molar ratios to give the mono- and diadducts 3 and 4a, b respectively. The reaction of 3 with thioamides in ethanol gave thiazoloquinoline diones 6a-d, whereas with acid amides in ethylene glycol, it gave oxazoloquinolinediones 12a-f.