Heterocycles. CXVIII. Pyridazines. LXVI. Novel method of annelation of the 1,2,4-triazole ring of the N2-C3 bond to azines

New Method for the General Synthesis of [1,2,4]Triazolo[1,5‐a]pyridines

“…The synthesis of this type of heterocycles has been previously reported in the literature by several synthetic methods such as amination of 2-aminopyridine with hydroxylamine-Osulfonic acid (HSA), followed by cyclization with formic acid (18-27 % overall yield); [1] reaction of 2-aminopyridines with DMF-dimethyl acetal, (DMF-DMA) followed by cyclization with HSA (26-87 % yield); [2] cyclization of N-iminopyridine with HCN (2 % yield); [3] isomerization of [1,2,4]-triazolo [4,3-a]pyridines in the presence of formic acid; [4] reaction of 2-aminopyridines with DMF-DMA and hydroxylamine, followed by cyclization with polyphosphoric acid (PPA) (54 % overall yield); [5] and acetylation of formamidoximes followed by heating in aqueous solution (2 steps, 25 % overall yield). [6] There are a number of significant disadvantages to these methods, including low yields and scope limitation.…”

“…[5] Several dehydrating agents were screened as leaving groups to evaluate whether they could promote the cyclization reaction more efficiently (Table 1).…”

Effects of civil war: scientific cooperation in the republics of the former Yugoslavia and the province of Kosovo

“…Thus, the case of a croatian scientist in Belgrade (Serbia) who cooperates with a croatian institution is treated as a cooperation between Serbia and Croatia. Polanc et al 1974;Berkowitz et al 1987). Additionally four papers from Belgrade and Novi Sad (both in Serbia) of this time period had ''Serbia Monteneg'' in their address field.…”

Synthesis of [1,2,3]triazolo[1,5-a][1,2,4]triazolo[5,1-c]pyrazines

“…We focused on the formation of 1,2,4-triazole ring fused to the N(5)=C(4)(NH 2 ) unit of the amine 1, 5 ( Figure 1), by the general synthetic method that use N,Ndimethylformamide dimethyl acetal (DMFDMA), hydroxylamine hydrochloride, and polyphosphoric acid (PPA) as the main required reagents, 7,8 thinking that this procedure could be extended to the heterocyclic system 1. …”