Mesomeric Betaines Based on Adamantylated 1,2,4-Triazolo[4,3-a]pyrimidin-5-ones: Synthesis, Structure and Conversion into Anionic N-Heterocyclic Carbenes

Ekaterina S Sheina; Tatyana S Shestakova; Sergey L Deev; Igor A Khalymbadzha; Pavel A Slepukhin; Oleg S Eltsov; Alexander S Novikov; Vadim A Shevyrin; Valery N Charushin; Oleg N Chupakhin

doi:10.1002/asia.202201306

Mesomeric Betaines Based on Adamantylated 1,2,4-Triazolo[4,3-a]pyrimidin-5-ones: Synthesis, Structure and Conversion into Anionic N-Heterocyclic Carbenes

Chem Asian J. 2023 Mar 1;18(5):e202201306. doi: 10.1002/asia.202201306. Epub 2023 Jan 30.

Authors

Ekaterina S Sheina¹, Tatyana S Shestakova¹, Sergey L Deev¹, Igor A Khalymbadzha^{1

2}, Pavel A Slepukhin^{1

2}, Oleg S Eltsov¹, Alexander S Novikov^{3

4}, Vadim A Shevyrin¹, Valery N Charushin^{1

2}, Oleg N Chupakhin^{1

2}

Affiliations

¹ Department of Organic and Biomolecular Chemistry, Ural Federal University, 19 Mira Str., Yekaterinburg, 620002, Russia.
² Postovsky Institute of Organic Synthesis, Ural Division of the Russian Academy of Sciences, 22 S. Kovalevskoy Str., Yekaterinburg, 620219, Russia.
³ Institute of Chemistry, Saint Petersburg State University, 7/9 Universitetskaya Nab., Saint Petersburg, 198504, Russia.
⁴ Рeoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya Str., Moscow, 117198, Russia.

PMID: 36662627
DOI: 10.1002/asia.202201306

Abstract

The C-N coupling of 1,2,4-triazolo[1,5-a]pyrimidin-7-ones with 1-adamantanol/1-bromoadamantane leads to 1,2,4-triazolo[4,3-a]pyrimidinium-5-olates, which are represented as mesomeric betaines (MBs). The formation of MBs involves not only N-alkylation of heterocyclic framework but also the rearrangement leading to a change in the type of fusion between pyrimidine and 1,2,4-triazole fragments. The structures of the obtained products were confirmed by the X-ray analysis and measurements of ¹³ C-¹³ C (J_CC ) coupling constants in the 1D ¹³ C NMR spectra of selectively ¹³ C-labeled samples. Treatment of the betaines with lithium bis(trimethylsilyl)amide (LiHMDS) gave anionic carbenes, which were detected by ¹³ C NMR spectroscopy and were trapped by reactions with phenyl isothiocyanate and sulfur. Density functional theory (DFT) and the quantum theory of atoms in molecules (QTAIM) analyses allowed for an insight into the electronic structure of the obtained betaines and N-heterocyclic carbene derivatives.

Keywords: NMR spectroscopy; alkylation; betaines; carbenes; heterocycles; isotopes; zwitterions.

Abstract

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