Current Organic Chemistry - Volume 22, Issue 28, 2018

Benzothiazole (BOT), the heterocyclic system consists of five-membered thiazole ring fused with the benzene ring. It is a very potent molecule because of its numerous pharmacological activities like anti-tumor, anti-microbial, anti-inflammatory, anticonvulsant, anti-diabetic, neuroprotective, calcium channel antagonist etc. Due to its extensive biological activities, it is still an interested area of research. Many scientists have discovered various methodologies for the synthesis of 2-aryl benzothiazoles and its derivatives by using different reaction conditions. 2-aryl benzothiazoles were synthesized via condensation of o-aminothiophenol with aldehydes. Previously, it had been synthesized using different types of catalysts to improve the selectivity, purity, and yield of the products. This review article mainly focuses on the synthesis of 2-arylbenzothiazoles using different reaction conditions from 2006 to 2018. This article is the detailed study of progressive environmental benign pathways for the synthetic strategies of 2-arylbenzothiazoles involving microwave assisted methods, ultra-sonication, use of nanoparticles, photo-assisted methods, metal catalysts, ionic liquids, mechanochemical grinding etc.

[1,2,3]-Benzotriazines represent an interesting category of heterocyclic compounds. Various synthetic methods, key reactions and biological aspects have been highlighted. In particular, some analogues have shown antitumor activity. [1,2,3]- Benzotriazin-4-one derivatives are applied extensively as herbicides, insecticides and nematicides. Incorporation of these compounds into the human food chain is a cause of concern, since their toxicity to man is well documented. This review is an attempt to discuss synthesis, chemical reactions, applications and pharmacological aspects of [1,2,3]- benzotriazine analogues from 1957 till date.

This review collects for the first time enantioselective domino reactions promoted by chiral green copper catalysts, covering the literature since the beginning of 2006. It is divided into two parts dealing successively with asymmetric two-component domino reactions and three-component processes. The first part is dedicated to twocomponent asymmetric domino reactions, including Michael-initiated processes, domino reactions based on cyclizations, domino reactions initiated by aldol-type condensations and Friedel–Crafts-initiated domino processes. The second part collects asymmetric threecomponent processes, such as Michael-initiated domino reactions, domino reactions between alkynes, aldehydes and amines, domino reactions based on 1,3-dipolar cycloadditions among the other three-component reactions.

Background: The synthesis of 6-membered pyrrololactams has been studied extensively over the past two decades, in particular because of the diverse biological activities ascribed to many marine-derived alkaloids with pyrrololactam structure. Consequently, many efforts to develop routes of synthesis for the preparation of a large variety of functionalized pyrrololactams have been reported. Objective: A summary of the progress made over the last 15 years is presented in this review. Eight different isomers of pyrrolopyridinone and the pyrrolopyrazinone bicyclic system are described. Major methods of forming the pyrrololactam system are divided into three general approaches, depending on whether they are based on: (1) derivatization of an existing pyrrole ring followed by cyclization; (2) the formation of a pyrrole framework on the existing 2-piperidinone scaffold; (3) the demethylation of 7-methoxy-azaindole. Special focus is placed on the new methods that have not been covered in other reviews and which mostly describe total synthesis of marine derived secondary metabolites. Conclusion: A broad range of modern synthetic methods is already available for the preparation of all eight regioisomers of the cyclic 6-membered pyrrolecarboxamide moiety. By presenting this review, we hope that the scientific community will be encouraged in developing novel synthetic routes for the preparation of this resourceful heterocyclic system and to include them as building blocks in the design of novel pharmacologically active compounds.

A reaction of 2-amino-N'-arylbenzamidines with triethyl orthoformate, orthoacetate and orthopropionate leads to quinazolin-4(3H)- imines. These compounds transform to 4-arylaminoquinazolines by heating in acetic acid according to the Dimroth rearrangement mechanism. Unexpectedly, these imines heated in ethanol gave mixtures of 4-arylaminoquinazolines and 4- ethoxy-quinazoline.