Transformations of 5-Diazo Derivatives of 1,3-Dimethyl-6-hydrazinouracil: New Synthetic Approaches to Novel Pyrimidine Derivatives

1,3-Dimethyl-6-hydrazinouracil 1 gives hydrazones 2 with the corresponding aldehydes. Heating of 6-hydrazinouracil 1 inethanol in the presence of hydrochloric acid results in the formation of N¹,N²-bis(1,3-dimethyl-2,6-dioxopyrimid-4-yl)hydrazine 3, which gives the diazo derivative 4 on treatment with 2,4-diazido-6-cyanomethoxy-s-triazine in DMSO in the presence of triethylamine at room temperature. 5-Diazo derivatives 5 (obtained under similar conditions from reactions between hydrazones 2 and the same 2,4-diazido-6-cyanomethoxy-s-triazine) are subsequently converted into triazolo[4.5-d]pyrimidines 6 in nearly quantitative yields after a short period of heating. Hydrazine 1 is transformed into the 2,4,7,9-tetramethyl-1,2,3,4,7,8,9,10-octahydropyrimido[4,5-c]-pyridazino[3,4-d]pyrimidin-1,3,8,10-tetrone 7 under diazo-transfer conditions.