Aryl-substituted 6,7-dihydropyrazolo[1,5-a]pyrimidine

Synthesis and antitumor evaluation of some new derivatives and fused heterocyclic compounds derived from thieno[2,3‐b]pyridine

“…The later intermediate has subjected to intramolecular cyclization via elimination of one molecule of water. [47,49] The appearance of a doublet at δ 1.24 ppm and a triplet at δ 4.14 ppm integrated for one and two protons corresponding to pyrimidine-C 4 -H and pyrimidine-C 5 -H, respectively, in the 1 H NMR spectrum confirmed the predicated structure.…”

“…The cyclocondensation mechanism was illustrated to proceed via initial Michael addition of the nucleophilic endocyclic pyrazole–NH to the electrophilic carbons in chalcone to yield an intermediate. The later intermediate has subjected to intramolecular cyclization via elimination of one molecule of water . The appearance of a doublet at δ 1.24 ppm and a triplet at δ 4.14 ppm integrated for one and two protons corresponding to pyrimidine–C 4 –H and pyrimidine–C 5 –H, respectively, in the 1 H NMR spectrum confirmed the predicated structure.…”

“…The 1 H NMR spectrum of compound 27 revealed a singlet signal at δ 3.89 ppm corresponding to OCH 3 protons. Many research workers reported the reaction of aminopyrazole derivatives with different chalcones to yield either dihydro [47,48] or aromatized [22,46,49] pyrazolo[l,5-a]pyrimidine derivatives depending on the reaction conditions. In this work, we synthesized 2,4-di(thiophen-2-yl)-3,4dihydropyrazolo[1,5-a]pyrimidine derivative 28 through treating of 3-amino-2H-pyrazole derivative 18 with 1,3di(thiophen-2-yl)-2-propen-1-one [50] in the presence of N,N-dimethylformamide.…”

Mini Review on The Synthesis and Biological Impact of Thiazoles

“…Cyclization of α-halocarbonyl compounds 9 with N-monosubstituted thioamides 10 afforded the corresponding thiazolium salt in promising yields 11. (Scheme 3) [22][23][24][25][26] Sarkis et al, has developed 2-monosubstituted aminothiazoles 13 via cyclization reaction of N-substituted thioureas 13 with halocarbonyl compounds 10. (Scheme 4) [27] On the other hand, 2-disubstituted aminothiazoles 16 can be obtained but in poor yield approximately ranging from 30 % to 70 % when N,N-disubstituted thioureas 15 was submitted to react with α-halocarbonyl 14 (Scheme 5).…”

Synthesis of structural analogues of Reversan by ester aminolysis: an access to pyrazolo[1,5-a]pyrimidines from chalcones

“…, β-diketones such as diaroylmethane), enones are rarely used because mixtures of products with the dihydro derivative (or perhaps some regioisomer) are obtained; more rigorous conditions or further steps are required to obtain the aromatic ring (Scheme 1a). 8,14–18…”