A Convenient Route to 5,6-Diphenyl-5,6-dihydro-uracils

Cyclopropenylium Cations, Cyclopropenones, and HeteroanaloguesRecent Advances

“…The product is different from that of the aforementioned cycloadditions, in that the CdC double bond in the cyclopropene ring has been converted to a CsC single bond due to the shift of hydrogen from nitrogen to these carbon atoms. Such reactions have been reported for guanidines 388 and 389, 297 isothioureas 390 341 and 391, 342 2-amino-1-azaazulenes 392, 343 and 2-aminobenzimidazole 393. 342 In contrast to the reaction of 392, where initial nucleophilic attack occurs by 1-aza nitrogen (see eq 206), the reactions of closely related compounds 2-hydrazino-1-azaazulene 394 344 and 2-(alkylamino)-1-azaazulenes 395 345 with diphenylcyclopropenone have been reported to start with attack at different positions, the terminal hydrazine nitrogen in 394 and C-3 and C-4 of the azulene ring in 395, to give mixtures of cycloadducts.…”

The chemistry of enaminones, diazocarbonyls and small rings: our contribution

“…It is interesting to note that urea does not react with 8a under the reaction conditions. 56 With the objective of evaluating the potential of the above reaction in the synthesis of bicyclic systems, a study of the reactivity of 8a with 2-aminothiazoles (80) and related compounds was undertaken. 57 The reactions of 80 with diphenylcyclopropenone led to the formation of 81 in average to very high yields.…”