Jiban Kumar Chakrabarti

Five-membered heterocyclic amines as potential anti-rheumatoid arthritis agents.

Abstract 5-Amino-3-substituted-1,2,4-thiadiazoles have been found to reduce the inflammatory and arthritic symptoms in the adjuvant arthritis model of rheumatoid arthritis.

A new route to nitriles. Dehydration of aldoximes using 2,4,6-trichloro-s-triazine (cyanuric chloride)

Nitriles are produced in good yields when aldoximes are treated with 2,4,6-trichloro-s-triazine in the presence of pyridine under mild conditions.

Heteroarene-fused benzodiazepines. Part 1. Synthesis of thieno-[2,3-b][1,5]-, -[3,2-b][1,5]-, and -[3,4-b][1,5]-benzodiazepinones

The synthesis of the 4H-thieno-[2,3-b][1,5]-, -[3,2-b][1,5]-, and -[3,4-b][1,5]-benzodiazepinone ring systems is described. Sodium methylsulphinylmethanide was used for the intramolecular cyclisation of the intermediate amino-esters (5), (9), and (14). However, attempted cyclisation of ethyl 2-(2-amino-4-fluoroanilino)-5-ethyl-thiophen-3-carboxylate (5b) with sodium hydride at a higher temperature caused rearrangement to a benzimidazolone (12).

Rearrangement of 2-[1(3h)-oxodihydrobenzo[c]furan-3-yl] quinuclidin-3-ones to tetrahydrobenzo[b]quinolizines. A novel synthesis of benzo[b]quinolizine ring systems.

Abstract A new two step synthesis of benzo[b]quinolizine ring systems via the rearrangement of 2-[1(3H)-oxodihydrobenzo[c]furan-3-yl] quinuclidin-3-ones is described.

s-Triazines. Part V. Synthesis and hydrolytic stability of 2,4-dihalogeno-6-heteroaryl-s-triazines

The first and second hydrolysis rate coefficients for the title compounds are discussed in terms of variation of the heteroaryl substituent (substituted phenyl, furyl, pyrrolyl, or thienyl) and of the halogen substituents (X = F, Cl, I, or CCl3). Electron-withdrawing substituents in the aryl rings enhance the rate coefficients, which are linearly related to the pKa values of the analogous dioxo-products (III) for phenyl, thienyl, or pyrrolyl substituents. Evidence is presented to show that the rate-determining step in the hydrolysis is nucleophilic attack on the triazine rather than carbon–halogen bond rupture.

Study of hydrolysis of amido-substituted γ-butyrolactones by pH-stat titration and ultraviolet spectroscopic analyses

pH-Stat titration and ultraviolet absorption spectroscopy have been used to study the rates of ring-opening in a series of gamma-butyrolactones and their analogues. The half-lives for the lactones can be related to Hammett inductive and steric parameters.

Chemistry of adamantane. Part IX. 1,2-Difunctional adamantanes; synthesis and reactions of protoadamantane-4-spiro-oxiran

The synthesis of protoadamantane-4-spiro-oxiran {octahydrospiro[2,5-methano-1H-indene-7,2′-oxiran]} and its isomerisation to protoadamantane-4-carbaldehyde are described. Electrophilic cleavage of the oxiran ring with simultaneous rearrangement gives 1,2-difunctional adamantane derivatives. Reactions of lithium carbenoids, from benzylidyne chloride and benzylidene bromide, with protoadamantan-4-one mainly lead to protoadamantan-4-yl phenyl ketone. 4-Phenylprotoadamantan-4-ols on treatment with acid preferentially undergo elimination to give 4-phenylprotoadamantene.

s-Triazines. Part I. Synthesis and reactions of dihalogeno-heteroaryl-s-triazines

Metallated derivatives of substituted or unsubstituted furans, thiophens, and pyrroles react with 2,4,6-trichloro-s-triazine (cyanuric chloride) to produce the corresponding 2,4-dichloro-6-(heteroaryl)-s-triazines. The effect of electrophilic substitution (nitration and bromination) on such ring systems is described.

Chemistry of adamantane. Part III. The synthesis and reactions of 1,2-disubstituted adamantane derivatives

Intramolecular reactions involving reactive species (e.g., acylnitrene and oxocarbene) have been applied to effect substitution at non-activated methylene-groups to obtain 1,2-difunctionalised adamantanes. The syntheses of tetrahydroadamantano[2,1-d]pyrimidin-2-one, a number of 2H-adamantano[1,2-e]pyridazin-3(4H)-ones, and their fully reduced derivatives are also reported.

2-Benzamido-4-phenylthiazoles as unexpected products of a novel rearrangement from the reaction of 2-bromo-1,3-bis(4-substituted)phenylpropane-1,3-diones and thiourea

A rearrangement leading to 2-benzamido-4-phenylthiazoles from the Hantzsch reaction under basic conditions is reported.