S. Selvaraj

Kinetics and mechanism of oxidation of substituted phenyl methyl sulphides by n-bromoacetamide

Abstract The kinetics of oxidation of several substituted phenyl methyl sulphides by N-bromoacetamide (NBA) in 80%acetonitrile-20%water (v/v) mixture are presented. The reaction is first order with respect to both sulphide and NBA and second order in Hg(II). The rate of the reaction exhibits inverse dependence on both [acetamide] and [NBA]. Electron-releasing substituents present in the phenyl ring of the sulphides accelerate the rate while electron-withdrawing ones retard it. The results are in accord with a mechanism involving the reaction between NBA-Hg(II) and sulphide-Hg(II) complexes in the slow rate-limiting step affording a sulphoniumion which hydrolyses in a subsequent fast step to the sulphoxide.

DIASTEREOSELECTIVE SYNTHESIS OF 2,2'-THIOBIS- AND 2,2'-SULFONYLBIS- (2-AROYL-3-ARYLOXIRANES)

Abstract Epoxidation of 2,2′-thiobis(1,3-diarylprop-2-en-1-ones) with H 2 O 2 NaOH in THF afforded a mixture of diastereomeric 2,2′-thiobis(2-aroyl-3-aryloxiranes) while the same reaction with its sulfonyl counterpart gave a single diastereomer.

1H, 13C and 17O NMR study of substituent effects in 4‐substituted phenylthiol esters

The 1H and 13C NMR spectra of 4‐substituted phenylthiol acetates, benzoates and cinnamates and the 17O NMR spectra of a few thiol acetates were measured. The 13C chemical shifts of C‐1 of the thiol esters when correlated with appropriate substituent‐induced chemical shifts (SCS) of monosubstituted benzenes reveal an enhancement of substituent effect at C‐1. Several good dual substituent parameter (DSP) correlations of 13C chemical shifts with σ1 and σR parameters were obtained for the carbons para to the substituent and the carbonyl carbons of all the three series of thiol esters display inverse substituent effects, indicating π‐polarization of the thiol ester functionality by the dipole of the substituent.

Novel tandem reactions of 2,2′-sulfonylbis(1,3-diarylprop-2-en-1-ones) with hydrazine: formation of 3,6-diarylpyridazines and 3,5-diarylpyrazoles

Abstract The 2,2′-sulfonylbis(1,3-diarylprop-2-en-1-ones) undergo tandem reactions with hydrazine affording 3,6-diarylpyridazines and 3,5-diarylpyrazoles unexpectedly, the latter predominating.

2,6-DIAROYL-3,5-DIARYL-4-METHYLTETRAHYDRO-1,4-THIAZINE-1,1-DIOXIDES - A SYNTHETIC AND STEREOCHEMICAL STUDY

Abstract Conjugate addition of methy lamine over 2,2′-sulfonylbis(1.3-diarylprop-2-en-1-ones) in dimethylformamide gave the hitherto unknown 2.6-diaroyl-3,5-diaryl-4-methyltetrahydro- 1.4-thiazine-1,1-dioxides in very good yields. The same thiazines were also obtained by condensation of bis(aroylmethyl)sulfones with aromatic aldehydes and methylamine. The structure and stereochemistry of the compounds were deduced from elemental analysis and spectral data.

DIASTEREOSELECTIVE SYNTHESIS OF 2,2′-THIOBIS- AND 2,2′-SULFONYLBIS- (1,3-DIARYLPROP-2-EN-1-ONES)—AN OXIDATIVE CONFIGURATIONAL SWITCH

Synthesis of some heretofore unknown 2,2′-thiobis(1,3-diarylprop-2-en-1-ones) and their oxidation to new 2,2′-sulfonylbis(1,3-diarylprop-2-en-1-ones) are reported. The stereochemistry of the sulfides and sulfones assigned as (Z,Z)- and (E,E)- respectively by X-ray diffraction studies reveals a configurational switch from (Z,Z)- to (E,E)-during oxidation.

Synthesis and multinuclear NMR study of (E)-s-trans -1-acetyl-5-aryl-3-styryl-2-pyrazolines

The reaction of triarylideneacetylacetones with hydrazine hydrate in acetic acid affords an excellent yield of (E)‐s‐trans‐1‐acetyl‐5‐aryl‐3‐styryl‐2‐pyrazolines via decinnamoylation. The structures of these compounds were elucidated using 1H, 13C and two‐dimensional NMR techniques such as H,H‐COSY, C,H‐COSY, NOESY and HMBC. 15N NMR data for these compounds were also obtained and the results are discussed. Copyright

SYNTHESIS AND NMR SPECTRAL STUDIES OF 2E, 6E-DIAROYL-3E, 5E-DIARYL -1,4-DITHIANE-1,1-DIOXIDES

The synthesis of some 2,6-diaroyl-3,5-diaryl-1,4-dithiane-1,1-dioxides was carried out by the conjugate addition of hydrogen sulphide to 2,2′-sulphonylbis(1,3-diarylprop-2-en-1-ones) and the complete assignment of their 1H and 13 C NMR chemical shifts made. The stereochemistry is found to be 2e,6e-diaroyl-3e,5e-diaryl-1,4-dithiane-1,1-dioxides from the NMR spectral data.

CONDENSATION REACTION OF BIS(AROYLMETHYL) SULFIDES WITH AROMATIC ALDEHYDES AND AMMONIUM ACETATE

Abstract Condensation reaction of bis(aroylmethyl) sulfides with aromatic aldehydes and ammonium acetate has been studied. The product obtained in each case is identified as 2,6-diaroyl-3,5-diaryltetrahydro-1,4thiazines by their analytical and spectral data. The stereochemistry of the products is also discussed. It is interesting to note that in most cases the only isomer isolable has the benzoyl group axially oriented.

A Simple and Efficient One-Step Synthesis of 2,4,10a-Triaryl-1,10a-Dihydro-2H-Pyrazino[2,1-b][1,3] Benzothiazoles Catalyzed by p-Toluene Sulfonic Acid

A series of 2,4,10a-triaryl-1,10a-dihydro-2H-pyrazino[2,1-b][1,3]benzothiazoles were prepared in good yields by the reaction of 2-[(2-oxo-2-arylethyl) anilino]-1-aryl-1-ethanones with 2-aminothiophenol in the presence of p-toluenesulfonic acid under solventless conditions. The products were characterized by 1H NMR and 13C NMR spectroscopy.