Structure and spectra of 1,3-dioxanes. II. Microwave spectrum, structural parameters, and ab initio calculations of 2-methyl-1,3-dioxane

Mamleev, A. Kh.; Gunderova, L. N.; Galeev, R. V.; Shapkin, A. A.; Faizullin, M. G.; Nikitina, A. P.; Shornikov, D. V.; Kantor, E. A.

doi:10.1007/s10947-007-0167-9

Cited by 6 publications

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“…In particular the great possibilities should be mentioned of the industrial application of cyclic acetals in the production of isoprene, 1,3-diols, and a number of drugs [1], and also in the synthesis of other six-membered 1,3,2-heterocyclic compounds [8], aminoalcohols and their derivatives [9]. The microwave spectroscopic studies established the geometrical characteristics of the most stable conformers of 2-methyl- [10], 4-methyl- [11], and 5-methyl-1,3-dioxanes [12]. The recent stereochemical studies actively utilized the quantum-chemical methods.…”

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Comparative conformational analysis of 1,3-dioxane and 1,3-dithiane

Кузнецов

2010

Russ J Org Chem

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It was shown by ab initio quantum-chemical approximations HF/6-31G(d) and MP2/6-31G(d)// HF/6-31G(d) that the conformational isomerization of 1,3-dioxane and 1,3-dithiane proceeded along common routes. The potential energy surface of both compounds contains six minima including the chair invertomers and enantiomeric fl exible forms. They are separated by several potential barriers. It was established by molecular dynamics method that the fl exible conformers at heating and keeping at 295-300 K transformed into each other and in the chair conformer.The interest to the structural investigation of 1,3-dioxanes and 1,3-dithianes originates from the features of their structure, their application in the industrial and fi ne organic synthesis, and also their promising physiologically active properties [1][2][3][4][5][6][7][8][9]. In particular the great possibilities should be mentioned of the industrial application of cyclic acetals in the production of isoprene, 1,3-diols, and a number of drugs [1], and also in the synthesis of other six-membered 1,3,2-heterocyclic compounds [8], aminoalcohols and their derivatives [9]. The microwave spectroscopic studies established the geometrical characteristics of the most stable conformers of 2-methyl-[10], 4-methyl- [11], and 5-methyl-1,3-dioxanes [12]. The recent stereochemical studies actively utilized the quantum-chemical methods. Thus in the framework of nonempirical approximations the minima on the potential energy suface (PES) were thoroughly studied for 1,3-dioxane [13] and 1,3-dithiane [14]. In the latter study also some transition states were investigated on the route of the conformational isomerization chairtwist and twist-twist. However up till now the general picture of the conformational transformations of the studied heterocyclic systems is absent in the literature. We formerly by the computer simulation established the main routes of the conformational isomerization both of the proper 1,3-dioxane [15] and its 2-methyl [16], 4-methyl [17], 4-phenyl [18], 4-trifl uoro methyl [19], 5-methyl [20], 5-isopropyl [21], and 2,5-dimethyl analogs [22]. This study concerns the comparative characteristic of the conformational isomerization of the molecules 1,3-dioxane (I) and 1,3-dithiane (II) by the use of ab initio approximations HF/6-31G(d) and МР2/6-31G(d)// HF/6-31G(d) calculated with HyperChem software [23]. O O I S S II According to 1 Н NMR data the molecules of the studied compounds at the room temperature undergo fast interconversion of the ring [2, 3, 24]. X X X X C inv CWe established that the PES of formals (I) and (II) contained six minima: invertomers of the chair and of fl exible forms. The routes of the conformational isomerization chair-chair (C-C inv) are identical in both compounds and suggest the interconversions by four independent routes through the conformers of flexible forms 2,5-twist-(2,5-Т) and 1,4-twist (1,4-Т). The

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