Hammett spectral correlations in some aryl 1,3-oxazine-4-thione derivatives

A series of some aryl 1,3-oxazine-4-thione derivatives have been synthesized by 1-methyl imidazole catalyzed three component one pot synthetic method in room temperature. The purities of these thiones were studied by their physical constants and spectroscopic data. The infrared and 13 C NMR spectral data of CN and CS were correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis. From the results of statistical analysis, the effect of substituent on the spectral data was studied.


1. General
All chemicals and solvents used in this present study were procured from Sigma-Aldrich and Merck companies. The infrared spectra of all oxazine imines have been recorded in SHIMADUZ Fourier Transform IR spectrophotometer using KBr disc. The NMR spectra of all compounds were recorded in BRUKER AV 400 type spectrometer, Using CDCl 3 as a solvent, 100 MHz frequency was applied for recording 13 C NMR spectra, taking TMS as standard.
where ν is the frequency for the substituted system, ρ is the reaction constants in terms of intercept, σ is the substituent constants and ν o is the frequency for the parent member of the series.
In 13 C nuclear magnetic resonance spectral correlations, the Hammett equation was used in the form as shown in (2): Log δ= Log δ 0 + ρσ …… (2) where δ 0 is the chemical shift of the corresponding parent compound.
Some of the individual correlations were fail in the statistical analysis for the correlation of chemical shifts (ppm) of δC=N, C=S. while seeking this with multi-parameter correlation with Swain-Lupton's [42] parameters, they gave satisfactory correlations. The generated multi-regression analysis equations are shown in (3-10).

CONCLUSIONS
There are nine aryl 1,3-oxazine-4-thione derivatives have been synthesized by 1-methyl imidazole catalyzed three component one pot synthetic method in room temperature. The purities of these thiones were studied by their physical constants and spectroscopic data. The infrared and 13 C NMR spectral data of CN and CS were correlated with Hammett substituent constants, F and R parameters using single and multi-linear regression analysis. The infrared νCN and νCS stretches (cm -1 ) were correlated satisfactorily with Hammett substituent constants, F and R parameters. Satisfactory correlation was obtained for the 13 C chemical shifts of δCN(ppm) of thiones with Hammett substituent constants, F and R parameters. The δCS(ppm) of thiones were failed in correlation. In multiple correlation all spectral frequencies gave satisfactorily correlation with Swain-Lupton's constants.