Synthesis and conformational properties of 1,3-dimethyl-3-phenyl-1,3-azasilinane. Low temperature dynamic NMR and computational study

Abstract

1,3-Dimethyl-3-phenyl-1,3-azasilinane was synthesized and its conformational behavior was studied by the low temperature NMR spectroscopy and quantum chemical calculations. The compound was shown to exist as an equilibrium mixture of the Ph ax Me eq and Ph eq Me ax chair conformers with the N-methyl substituent in equatorial position. The barrier to ring inversion was also determined.

1,3-Dimethyl-3-silapiperidine: Synthesis, Molecular Structure, and Conformational Analysis by Gas-Phase Electron Diffraction, Low Temperature NMR, IR and Raman Spectroscopy, and Quantum Chemical Calculations

“…The advantage of the use of urea instead of tertiary amines as a scavenger of HCl in the second step is that the formed urea hydrochloride is easily separated from the substitution product 4 . Finally, because of a high lability of the Si–H bond, the target product in the last step was isolated without water workup, according to a modified procedure . Because of formation of hardly separable byproducts, the intermediate products 3 , 4 were used in the next step without further purification.…”

“…As follows from the literature data, the only two compounds that allow correct estimation of the conformational energy of the methyl group attached to silicon are 1-methyl-1-silacyclohexane and 3-methyl-1,3-thiasilinane. Recently we have studied a series of 3-silapiperidines (1,3-azasilinanes) bearing two substituents at silicon and different N -alkyl groups. − However, the lack of a reference point (here, 1,3-dimethyl-3-silapiperidine) does not allow us to analyze the conformation energies A in various silaheterocyclohexanes as a function of the nature of the heteroatom and the substituent at silicon. With this in mind, the goal of the present study was to synthesize the first Si–H-containing azasilaheterocycle, 1,3-dimethyl-3-silapiperidine 1 , and to investigate its structure and conformational behavior experimentally (gas-phase electron diffraction, low temperature NMR, IR and Raman spectroscopy) and theoretically (DFT, MP2, CCSD(T), NBO analysis).…”

Molecular Structure and Conformational Analysis of 1-Phenyl-1-X-1-Silacyclohexanes (X = F, Cl) by Electron Diffraction, Low-Temperature NMR, and Quantum Chemical Calculations

“…The analogues of 1 , 3,3-disubstituted 1-aza­(oxa,thia)-3-silacyclohexanes ZC 4 H 8 SiXY ( 2 ), have also been synthesized and studied, such as azasilacyclohexanes ( 2 , Z = NR; X, Y = Ph, Me; , X, Y = Me, OR), oxasilacyclohexanes ( 2 , Z = O; X, Y = Ph, Me; X, Y = Me, OR), and thiasilacyclohexanes ( 2 , Z = S; X, Y = Ph, Me; X, Y = Me, F).…”

“…2 The structurally and conformationally investigated 1,1disubstituted 1-silacyclohexanes C 5 H 10 SiXY (1) are so far limited to five pairs of substituents X and Y: Me, F; 3 Me, Cl; 4 Me, CF 3 ; 3 Cl, SiCl 3 ; 5 and Me, Ph. 2 The analogues of 1, 3,3-disubstituted 1-aza(oxa,thia)-3silacyclohexanes ZC 4 H 8 SiXY (2), have also been synthesized and studied, such as azasilacyclohexanes (2, Z = NR; X, Y = Ph, Me; 6,7 X, Y = Me, OR 8 ), oxasilacyclohexanes (2, Z = O; X, Y = Ph, Me; 9 X, Y = Me, OR 10 ), and thiasilacyclohexanes (2, Z = S; X, Y = Ph, Me; 2 X, Y = Me, F 11 ).…”

Synthesis, Reactivity, Functionalization, and ADMET Properties of Silicon-Containing Nitrogen Heterocycles

“…Most known procedures report the construction of rings bearing kinetically stable endocyclic silicon–heteroatom bonds, which we sought to avoid. Syntheses of silaheterocycles containing carbon-flanked silicon are more relevant, but only a few construct rings bearing sites for functionalization, which necessitated either the development of new synthetic procedures or optimization of existing methods for multi-gram-scale preparations.…”