Theoretical and experimental 1H, 13C and 15N NMR spectra of monomethyl substituted tetramethyl 9aH- and 4H-quinolizine-1,2,3,4-tetracarboxylate

Since our previous review article (Curr. Org. Chem. 2002, 6, 35), significant improvements and an array of 15 N NMR applications in structural analysis have been published. This report aims to update coverage of improvements in methodology and various types of applications published over the period 2001 -2005. Substantial progress in cryogenic probe technology and the commercial availability of cryoprobes have facilitated the measurement of 15 N NMR parameters.The number of solid-state applications has increased significantly during the past few years. In contrast to our previous review, this article covers 15 N solid-state studies. The 15 N NMR chemical shifts of organic molecules are routinely measured by using cross-polarization magic-angle spinning (CP/MAS) techniques. The principal values of the chemical shift tensors can also be determined. 1 H-15 N and 2 H-15 N distance measurements made by means of 1 H detection are currently used in NMR crystallography.User friendly quantum chemical programs allow for the routine calculation of 15 N chemical shielding and indirect spinspin coupling constants, especially using density functional theory (DFT).Applications of 15 N NMR spectroscopy in various fields of chemistry are summarized here. Major sections represent tautomerism, complexation, protonation, and hydrogen bonding. The other topics comprise N-alkylation, N-oxidation, regioisomerism, and changes in configuration or conformation.

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“…Bednarek et al [289] have studied derivatives of 9aH-(A) and 4H-(B) quinolizine-1,2,3,4-tetracarboxylate (18).…”

Section: -Di(pyridin-2-yl)ethene-12-diol (A) Over 2-hydroxy-12-di(mentioning

confidence: 99%

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

Marek¹,

Lyčka²,

Kolehmainen³

et al. 2007

COC

133

110

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¹H chemical shifts in NMR. Part 21—Prediction of the ¹H chemical shifts of molecules containing the ester group: a modelling and ab initio investigation

Abraham

Bardsley

Mobli

et al. 2004

Magnetic Reson in Chemistry

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The 1H NMR spectra of 24 compounds containing the ester group are given and assigned. These data were used to investigate the effect of the ester group on the 1H chemical shifts in these molecules. These effects were analysed using the CHARGE model, which incorporates the electric field, magnetic anisotropy and steric effects of the functional group for long-range protons together with functions for the calculation of the two- and three-bond effects. The effect of the ester electric field was given by considering the partial atomic charges on the three atoms of the ester group. The anisotropy of the carbonyl group was reproduced with an asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond with values of Deltachi(parl) and Deltachi(perp) of 10.1 x 10(-30) and -17.1 x 10(-30) cm3 molecule(-1). An aromatic ring current (=0.3 times the benzene ring current) was found to be necessary for pyrone but none for maleic anhydride. This result was confirmed by GIAO calculations. The observed 1H chemical shifts in the above compounds were compared with those calculated by CHARGE and the ab initio GIAO method (B3LYP/6-31G**). For the 24 compounds investigated with 150 1H chemical shifts spanning a range of ca 10 ppm, the CHARGE model gave an excellent r.m.s. error (obs - calc) of <0.1 ppm. The GIAO calculations gave a very reasonable r.m.s. error of ca 0.2 ppm although larger deviations of ca 0.5 ppm were observed for protons near to the electronegative atoms. The accurate predictions of the 1H chemical shifts given by the CHARGE model were used in the conformational analysis of the vinyl esters methyl acrylate and methyl crotonate. An illustration of the use of the CHARGE model in the prediction of the 1H spectrum of a complex organic molecule (benzochromen-6-one) is also given.

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Bicyclic 6-6 Systems with One Bridgehead (Ring Junction) Nitrogen Atom: No Extra Heteroatom

Avendaño

Menéndez

2008

Comprehensive Heterocyclic Chemistry III

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Theoretical and experimental 1H, 13C and 15N NMR spectra of monomethyl substituted tetramethyl 9aH- and 4H-quinolizine-1,2,3,4-tetracarboxylate

Cited by 4 publications

References 14 publications

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

¹H chemical shifts in NMR. Part 21—Prediction of the ¹H chemical shifts of molecules containing the ester group: a modelling and ab initio investigation

Bicyclic 6-6 Systems with One Bridgehead (Ring Junction) Nitrogen Atom: No Extra Heteroatom

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Theoretical and experimental 1H, 13C and 15N NMR spectra of monomethyl substituted tetramethyl 9aH- and 4H-quinolizine-1,2,3,4-tetracarboxylate

Cited by 4 publications

References 14 publications

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

1H chemical shifts in NMR. Part 21—Prediction of the 1H chemical shifts of molecules containing the ester group: a modelling and ab initio investigation

Bicyclic 6-6 Systems with One Bridgehead (Ring Junction) Nitrogen Atom: No Extra Heteroatom

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¹H chemical shifts in NMR. Part 21—Prediction of the ¹H chemical shifts of molecules containing the ester group: a modelling and ab initio investigation