Abstract Treatment of 6-arylthiouracils with the Vilsmeier reagent (dimethylformamide- phosphorus oxychloride) gave the corresponding 6-arylthio-5-formyluracils, which could alternatively be prepared by the condensation of 6-chloro-5-formyluracils with thiophenols. Dehydrative cyclization of the above 5-formyluracils with polyphosphoric acid gave 1- benzothiopyrano [2, 3-d] pyrimidine-2, 4-(3H) diones (10-thia-5-deazaflavins). These 10- ...
