Aurimas Bieliauskas

On the Tautomerism of N-Substituted Pyrazolones: 1,2-Dihydro-3H-pyrazol-3-ones versus 1H-Pyrazol-3-ols

The tautomerism of 1-phenyl-1,2-dihydro-3H-pyrazol-3-one was investigated. An X-ray crystal structure analysis exhibits dimers of 1-phenyl-1H-pyrazol-3-ol units. Comparison of NMR (nuclear magnetic resonance) spectra in liquid state (1H, 13C, 15N) with those of “fixed” derivatives, as well as with the corresponding solid state NMR spectra reveal this compound to exist predominantly as 1H-pyrazol-3-ol molecule pairs in nonpolar solvents like CDCl3 or C6D6, whereas in DMSO-d6 the corresponding monomers are at hand. Moreover, the NMR data of different related 1H-pyrazol-3-ol derivatives are presented.

L-Proline and related chiral heterocyclic amino acids as scaffolds for the synthesis of functionalized 2-amino-1,3-selenazole-5-carboxylates

A series of methyl 2-amino-1,3-selenazole-5-carboxylates possessing a chiral pyrrolidin-2-yl, piperidin-2-yl, or piperidin-3-yl substituent at the C-4 atom of the heteroaromatic ring was designed and synthesized. In the first stage of the synthesis, the carboxylic acid functional group of the L-proline or related chiral heterocyclic amino acid was converted to the corresponding β-keto ester, which was then α-brominated with N-bromosuccinimide. The subsequent reaction of the α-brominated β-keto ester with selenourea afforded the target methyl 2-amino-1,3-selenazole-5-carboxylate. The structures of the novel heterocyclic compounds were confirmed by 1H, 13C, and 77Se NMR spectroscopy and HRMS.

10a,11,11-Trimethyl-10a,11-dihydro-8H-benzo[e]imidazo[1,2-a]indol-9(10H)-one

The alkylation of 1,1,2-trimethyl-1H-benzo[e]indole with 2-chloroacetamide, followed by work-up of the reaction mixture with a base and the subsequent treatment of a crude product with acetic acid gives 10a,11,11-trimethyl-10a,11-dihydro-8H-benzo[e]imidazo[1,2-a]indol-9(10H)-one. The structure assignments were based on data from 1H, 13C, and 15N-NMR spectroscopy. The optical properties of the obtained compound were studied by UV–Vis and fluorescence spectroscopy.