Reactions of 4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidines with α,β‐unsaturated carbonyl compounds

Abstract

Reactions of 4,7-Dihydro-1,2,4-triazolo [1,5-a]pyrimidines with α,β-Unsaturated Carbonyl Compounds Victoria V. Lipson[a], Irina V. Ignatenko[a], Sergey M. Desenko[b], Svetlana V. Shishkina[b], OlegThe reaction of 5,7-diphenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine (1) with α,β-unsaturated carbonyl compounds 2a-f led to the formation of the alkylated heterocycles 3a-f (Figure 1). However, the reaction of 5-methyl-7-phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine (5) with 2a-c yielded under the same conditions the triazolo[5,1-b]quinazolines 6a-c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, 1 H and 13 C nmr measurements and on an X-ray diffraction study.

Unusual heterocyclization of chalcone podands with 3-amino-1,2,4-triazole

“…In addition, the structural similarity (X ray diffraction data) of crownophanes 7 and 11 is obvious and comes to the ) is identical to that of similar fragment in crownophane 11 and differs from that described earlier for the β adduct with chalcone. 34 Another indirect confirmation of the initial sequence of intermolecular and intramolecular Michael additions (see Scheme 2, path A) can be the antiparallel stereoorien tation of the terminal chalcone groups in the starting com pound 1, which is observed in the geometry of crowno phanes 7 and 11 (see Fig. 4, b, c).…”

Synthesis and chemical transformations of partially hydrogenated [1,2,4]triazolo[5,1-b]quinazolines

“…The synthesis of this compound has been described recently. 15 It appeared that compound 12, unlike dihydrotriazolo pyrimidine 1 studied earlier, 16 is stable to aqueous and alcoholic solutions of HCl (1 : 1). Even prolonged reflux ing of triazoloquinazoline 12 under the above mentioned conditions did not lead to hydrolysis of this compound.…”

“…An alternative approach to the desired compounds is associated with the formation of the five membered azole ring based on the already present quinazoline moiety, but this method is synthetically more limited. 14 Recently, 15 we have described yet another procedure for the synthesis of [1,2,4]triazolo [5,1 b]quinazolines, which differs from the above mentioned methods in that the carbocycle closure occurs on the basis of the already present partially hydro genated 5 methyl 7 phenyl 1,2,4 triazolo[1,5 a]pyrimi dine system with the involvement of 1,3 diaryl 2 propen 1 ones in an alcoholic medium in the presence of MeONa.…”

“…The yield was 0.21 g (53%). 7 Hydroxy 5,6,8 triphenyl 6,7 dihydro[1,2,4]triazo lo[5,1 b]quinazoline (15). Selenium dioxide (0.26 g, 2.5 mmol) was added to a solution of compound 12 (0.8 g, 2 mmol) in AcOH (10 mL).…”

“…This is consistent with the pathway of the reaction of dihydro 1,2,4 triazo lo[1,5 a]pyrimidines with benzylideneacetophenones de scribed earlier. 15 We studied the chemical properties of partially hydro genated triazoloquinazolines, such as the ability to undergo hydrolysis, oxidation, reduction, and alkyla tion (Scheme 2), using 5,6,8 triphenyl 5,6,7,10 tetra hydro [1,2,4] (12) as an ex ample. The synthesis of this compound has been described recently.…”