¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• complicated the subsequent NMR analysis. Meanwhile, the application of [2,3-15N2]-5-aminotetrazole 7-15N2 provided the single double-labelled products in the tetrazolo[1,5-a]pyrimidine series [33]. Thus, in the current work, [2,3-15N2]-5-aminotetrazole 7-15N2 (98% enrichment for each of the labelled 15N atoms

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

• Elisandra Scapin,
• Paulo R. S. Salbego,
• Caroline R. Bender,
• Alexandre R. Meyer,
• Anderson B. Pagliari,
• Tainára Orlando,
• Geórgia C. Zimmer,
• Clarissa P. Frizzo,
• Helio G. Bonacorso,
• Nilo Zanatta and
• Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 2396–2407, doi:10.3762/bjoc.13.237

• theory (DFT) for energetic and molecular orbital (MO) calculations. Keywords: 5-aminotetrazol; azide–tetrazole equilibrium; 2-azidopyrimidine; β-enaminones; tetrazolo[1,5-a]pyrimidine; trifluoromethylatedtetrazolo[1,5-a]pyrimidines; Introduction Tetrazolo[1,5-a]pyrimidines have attracted attention in

• using ultrasound irradiation promoted shorter reaction times, high regioselectivity, and excellent yields, when compared with conventional thermal heating [30]. Presently, we demonstrate an eco-friendly synthesis of 5- and 7-substituted tetrazolo[1,5-a]pyrimidine isomers, in good to excellent yields

• the β-enaminone precursor and (iii) elucidate the azide–tetrazole equilibrium when the compound is in solid form or dissolved in distinct solvents. The tetrazolo[1,5-a]pyrimidine synthesis was conducted from a cyclocondensation reaction of the type [CCC + NCN], in which the CCC block is a series of β

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles

• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess and
• Viktor I. Saloutin

Beilstein J. Org. Chem. 2015, 11, 385–391, doi:10.3762/bjoc.11.44

• tetrazolylaminomethylidene derivative B. As a result of regiospecific addition of NH-group to acyl fragment, the intermediate B gives dihydrotetrazolo[1,5-a]pyrimidine C, which is further transformed into tetrazolo[1,5-a]pyrimidine D after elimination of water. Because of the ability of tetrazole to ring opening at the N1

• –N8 bond, tetrazolo[1,5-a]pyrimidine D undergoes azide–tetrazole isomerism to form isomeric 2-azidopyrimidines 2a–c. The electron-withdrawing substituents in the heterocycle are known to facilitate the opening of the fused tetrazole ring because of decreased electron density at the bridgehead nitrogen

• derivative 6 was not observed even after refluxing for 48 h. Cyclization of compound 6 into tetrazolopyrimidine 7 was performed under prolonged heating without the base. The structure of tetrazolo[1,5-a]pyrimidine 7 was confirmed by IR, 1H, 13C, 2D 1H,13C and 2D 1H,15N HMBC NMR spectra. Thus, the IR spectrum