A synthesis of 6-functionalized 4,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidines

6-Unsubstituted 7-R-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines (R = H or Me) were synthesized via two pathways: (a) deacylation of the corresponding 5-acetyl Biginelli-like precursors in KOH/H₂O and (b) reduction of the corresponding 1,2,4-triazolo[1,5-a]pyrimidines using LiAlH₄. The products could be easily formylated at position 6, which is promising for the further synthesis of functionalized 6-substituted derivatives of 4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines. In contrast, 6-acetyl-7-(4-(N,N-dimethylaminophenyl))-5-methyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine undergoes a cascade process in KOH/H₂O, leading to the formation of a 4,5,8,9-tetrahydro[1,2,4]triazolo[5,1-b]quinazoline derivative.     

Cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with hydroxylamine and hydrazine

The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine ( 4a ) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine ( 4b ), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane ( 5 ). The structure determination of the compounds obtained is based on ¹H and ¹³C nmr spectra including NOE measurements.     

Aminoazoles in the three-component synthesis of 7-substituted 6-ethoxycarbonyl-5-methyl-4,7-dihydroazolo[1,5-a]pyrimidines

The three-component synthesis of 7-substituted 6-ethoxycarbonyl-5-methyl-4,7-dihydroazolo[1,5-a]pyrimidines was carried out for the first time by the reactions of aminoazoles (3-aminopyrazole, 3-amino-1,2,4-triazole, or 5-aminotetrazole) with acetoacetic ester and aliphatic, aromatic, or heteroaromatic aldehyde.     

Synthesis of 8,9-dihydro[1,2,4]triazolo[1,5-a]-quinazolin-6(7H)-one derivatives

Regioselectivity of the reactions of 1H-1,2,4-triazol-3-amines with 2-acyl-5,5-dimethylcyclohexane-1,3-diones and 2-dimethylaminomethylidene-5,5-dimethylcyclohexane-1,3-dione was studied. In all cases, the products were substituted 8,9-dihydro[1,2,4]triazolo[1,5-a]quinazolin-6(7H)-ones whose structure was determined by ¹H and ¹³C NMR spectroscopy.     

Thermolysis of [1,2,4]triazolo[1,5-a]pyrimidine n-ylides

5,7-Dimethyl[1,2,4]triazolo[1,5-a]pyrimidinio-3-phenacylide ($\text{3}$) generated by the reaction of an iminium salt ($\text{2}$) with 1 eq. of triethylamine, underwent a new thermal ring cleavage of the triazole moiety to give the pyrimidine derivative. However reaction of $\text{2}$ with 2 eq. of triethylamine afforded the 2-iminooxazoline derivative. The iminooxazoline reacted with nucleophiles such as alcohols or amines to give imidazoles.     

Synthesis of (7-Aryl-5-methyl-4,7-dihydrotetrazolo[1,5-a]pyrimidin-6-yl)(phenyl)methanones

Russian Journal of Organic Chemistry - (7-Aryl-5-methyl-4,7-dihydrotetrazolo[1,5-a]pyrimidin-6-yl)(phenyl)methanones were synthesized by three-component condensation of 1-phenylbutane-1,3-dione...     

Molecular and crystal structure of 5,7-diphenyl-7-methyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine

The molecular and crystal structures of 5,7-diphenyl-7-methyi-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine have been studied by X-ray structural methods. The crystal is monoclinic,a=16.112(3),b=13.489(3),c=14.480(3)Å, =101.62(2)°,Z=8, space groupC2/c,R=0.071. The presence of short intermolecular contacts indicates considerable steric strain in the molecule. The dihydropyrimidine ring exists in an unevenly planar boat conformation. Increasing the steric strain of the dihydrocycle leads to a twisted conformation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1912–1914, November, 1993.     

Synthesis of N,7-diaryl-5-methyl-4,7-dihydro-1,2,4-triazolo[1,5-a]-pyrimidine-6-carboxamides

Reaction of N-arylamides of acetoacetic acid with aromatic aldehyde and 3-amino-1,2,4-triazole derivatives has resulted in N,7-diaryl-5-methyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxamides.     

New protocols for the synthesis of 5-amino-7-(4-phenyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate esters using an efficient additive

This work introduces a new additive named 4,4’-trimethylenedipiperidine for the practical and ecofriendly preparation of ethyl 5-amino-7-(4-phenyl)-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate derivatives. This chemical is commercially available and easy to handle. It also possesses a low melting point and a broad liquid range temperature, high thermal stability, and good solubility in water. Based on green chemistry principles, the reaction was performed in a) a mixture of green solvents i.e. water and ethanol (1:1 v/v) at reflux temperature, and b) the additive was liquefied at 65 °C and the reaction was conducted in the liquid state of the additive. High yields of the desired triazolo-pyrimidines were obtained under both aforementioned conditions. Our results demonstrated that this additive, containing 2 Lewis base sites and able to act as an acceptor-donor hydrogen bonding group, is a novel and efficient alternative to piperidine, owing to its unique properties such as its reduced toxicity, nonflammable nature, nonvolatile state, broad liquid range temperature, high thermal stability, and ability to be safely handled. Furthermore, this additive could be completely recovered and exhibited high recyclability without any change in its chemical structure and no significant reduction in its activity. The current methodology has several advantages: (a) it avoids the use of hazardous materials, as well as toxic, volatile, and flammable solvents, (b) it does not entail tedious processes, harsh conditions, and the multistep preparation of catalysts, (c) it uses a metal-free and noncorrosive catalyst, and (d) reduces the generation of hazardous waste and simple work-up processes. The most important result of this study is that 4,4’-trimethylenedipiperidine can be a promising alternative for toxic, volatile, and flammable base reagents in organic synthesis owing to its unique properties.     

Palladium(II) and platinum(II) organometallic complexes with 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine. Antitumor activity of the platinum compounds

Palladium and platinum complexes with HmtpO (where HmtpO=4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine, an analogue of the natural occurring nucleobase hypoxanthine) of the types [M(dmba)(PPh3)(HmtpO)]ClO4[dmba=N,C-chelating 2-(dimethylaminomethyl)phenyl; M=Pd or Pt], [Pd(N-N)(C6F5)(HmtpO)]ClO4[N-N=2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), or N, N, N', N'-tetramethylethylenediamine (tmeda)] and cis-[M(C6F5)2(HmtpO)2] (M=Pd or Pt) (head-to-head atropisomer in the solid state) have been obtained. Pd(II) and Pt(II) complexes with the anion of HmtpO of the types [Pd(tmeda)(C6F5)(mtpO)], [Pd(dmba)(micro-mtpO)] 2, and [NBu4]2[M(C6F5)2(micro-mtpO)]2(M=Pd or Pt) have been prepared starting from the corresponding hydroxometal complexes. Complexes containing simultaneously both the neutral HmtpO ligand and the anionic mtpO of the type [NBu4][M(C6F5)2(HmtpO)(mtpO)] (M=Pd or Pt) have been also obtained. In these mtpO-HmtpO metal complexes, for the first time, prototropic exchange is observed between the two heterocyclic ligands. The crystal structures of [Pd(dmba)(PPh 3)(HmtpO)]+, cis-[Pt(C6F5)2(HmtpO)2].acetone, [Pd(C6F5)(tmeda)(mtpO)].2H2O, [Pd(dmba)(micro-mtpO)]2, [NBu4]2[Pd(C6F5)2(micro-mtpO)]2.CH2Cl2.toluene, [NBu4]2[Pt(C6F5)2(micro-mtpO)](2).0.5(toluene), and [NBu4][Pt(C6F5)2(mtpO)(HmtpO)] have been established by X-ray diffraction. Values of IC50 were calculated for the new platinum complexes cis-[Pt(C6F5)2(HmtpO)2] and [Pt(dmba)(PPh3)(HmtpO)]ClO4 against a panel of human tumor cell lines representative of ovarian (A2780 and A2780 cisR), lung (NCI-H460), and breast cancers (T47D). At 48 h incubation time, both complexes were about 8-fold more active than cisplatin in T47D and show very low resistance factors against an A2780 cell line, which has acquired resistance to cisplatin. The DNA adduct formation of cis-[Pt(C6F5)2(HmtpO)2] and [Pt(dmba)(PPh3)(HmtpO)]ClO4 was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by these platinum complexes on plasmid DNA pB R322 were also obtained.     

Tautomeric forms of 5-(2-hydroxyphenyl)-7-phenyldihydro-1,2,4-triazolo[1,5-a]pyrimidine

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1000–1001, July, 1989.     

A synthesis of 6-functionalized 7-unsubstituted- and 7-methyl[1,2,4]azolo[1,5-a]pyrimidine derivatives

6-Functionalized 7-R-4,7-dihydro[1,2,4]azolo[1,5-a]pyrimidines (R?=?H or Me) were synthesized by Biginelli-like reaction of formaldehyde or acetaldehyde, aminoazoles, and corresponding β-dicarbonyl precursor. Alkylation of the obtained compounds proceeds smoothly at position 4, while oxidation leads to 7-R-[1,2,4]azolo[1,5-a]pyrimidines formation. 6-Ethoxycarbonyl derivatives could be reduced to the corresponding alcohols by LiAlH₄ and hydrolyzed to the acids.     

2-aryl(hetaryl)-4H-[1,2,4]triazolo[1,5-a]benzimidazoles

2-(4-Methylphenyl)-4H-[1,2,4]triazolo[1,5-a]benzimidazole and its previously unknown 2-(2-furyl)- and 2-(2-thienyl)-substituted analogs were synthesized by cyclization of benzimidazole-1,2-diamine with the corresponding carboxylic acid chlorides. The IR, ¹H, ¹³C, and ¹⁵N NMR, and mass spectra of the cyclization products in combination with the results of quantum-chemical calculations of NMR chemical shifts showed radical differences of [1,2,4]triazolo[1,5-a]benzimidazoles having no substituent on N⁴ from the recently reported low-melting products of oxidation of 2-amino-1-arylmethylideneaminobenzimidazoles with (diacetoxy-λ³-iodanyl)benzene, which, as we believe, were erroneously assigned analogous structure.     

2-苄硫(砜)基-5-甲基-7-取代苄氧基-1,2,4-三唑并[1,5-a]嘧啶类衍生物的合成及抑菌活性研究

以2-苄硫基-5-甲基-7-羟基-1,2,4-三唑并[1,5-a]嘧啶为起始原料,经过醚化、氧化反应分别合成了12个新型的2-苄硫基-5-甲基-7-取代苄氧基-1,2,4-三唑并[1,5-a]嘧啶类化合物5a～5l及其砜基类似物6a～6l,并通过1H NMR,IR,MS和元素分析对所有目标化合物进行了结构表征.初步生物活性测试结果表明,在50μg/mL浓度下,部分化合物表现出了一定的抑菌活性,其中化合物5c,5k和5l对黄瓜灰霉病菌的抑制率分别为61%,69%和85%.