ChemInform Abstract: Structure and Ambident Reactivity of Phenylpemoline.

Рамш, С. М.; Храброва, Е. С.; Гинак, А. И.

doi:10.1002/chin.198942139

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“…Experimental studies on the amino-imino tautomerism of 2-aminothiazolidine-4-one have been reported in several papers. [2][3][4][5][6][7][8][9][10][11][12][13][14] However, the opinions of the authors are contradictory. Amirthalingam and Muralidharan 7 have confirmed by X-ray the existence of the imino form of pseudothiohydantoin.…”

Section: Introductionmentioning

confidence: 99%

“…By means of IR spectroscopy, Khovratovich and Chizhevskaya 5 have shown that in chloroform solution the amino form exists. According to Ramsh et al 11 (IR and NMR data), in DMSO and in water solutions pseudothiohydantoin exists as amino tautomer. Studies 13 of 2-aminothiazolidine-4one and its isomer 4-aminothiazolidine-2-one have been carried out by IR and 1 H and 13 C NMR spectroscopy in DMSO solution and have shown that 2AT exists in amino form while 4AT in imino form.…”

Section: Introductionmentioning

confidence: 99%

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Ab Initio Study of 2,4-Substituted Azolidines. II. Amino−Imino Tautomerism of 2-Aminothiazolidine-4-one and 4-Aminothiazolidine-2-one in Water Solution

2005

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The relative stabilities of the tautomers of 2-aminothiazolidine-4-one and 4-aminothiazolidine-2-one were calculated at the MP2/6-31+G(d,p) level by considering their mono- and trihydrated complexes. Single-point calculations at the MP4/6-31+G(d,p)//MP2/6-31+G(d,p) level of theory were performed to obtain more accurate energies. The values of proton transfer barriers in the isolated, mono- and trihydrated tautomers of 2-aminothiazolidine-4-one (2AT) and 4-aminothiazolidine-2-one (4AT) were calculated for two different mechanisms of tautomerisation. In the absence of water, the process of proton transfer should not occur. Addition of water molecules decreases the barrier making the process faster, as the participation of two water molecules in a proton transfer reaction is more favorable than the participation of only one water molecule. To estimate the effect of the medium (water) on the relative stabilities of the tautomers of the studied compounds we applied the polarizable continuum model (PCM). (13)C NMR chemical shieldings were calculated using the GIAO approach at MP2/6-31+G(d,p) optimized geometries. HF and the DFT B3LYP functional with 6-31+G(d,p) basis set were employed. The quantum chemical results for the chemical shifts in gas phase and in polar solvents (water and DMSO) were compared with experimental data. TD DFT B3LYP/aug-cc-pVTZ calculations were performed to predict the absorption maxima of tautomers A and B of 2AT and 4AT.

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