Telescoped Oxidation and Cycloaddition of Urazoles to Access Diazacyclobutenes.

Our previous method to access the diazacyclobutene scaffold did not allow for modification of the substituent originating from the 1,2,4-triazoline-3,5-dione component. We have circumvented this challenge and expanded access to additional structural diversity of the scaffold. A telescoped urazole oxidation and Lewis acid-catalyzed cyclization provided R3-substituted diazacyclobutenes. Calcium hypochlorite-mediated oxidation of urazoles followed by MgCl2-catalyzed cyclization of the resulting triazolinediones with thioalkynes promoted the formation of diazacyclobutenes bearing substitution at the R3 position originating from the triazolinedione component.