Organoiodines in the Synthesis and Functionalization of Some Novel Bioactive Heterocycles

Abstract

Over the past decade, there has been unparalleled growth in the use of rganoiodine reagents in the construction of various heterocycles due to their inherent low toxicity, high stability and commercial newlineavailability. The highly selective oxidizing properties associated with organoiodine reagents, make them superior to toxic heavy metal-based oxidants to carry out many useful organic transformations. The present thesis deals with the utilization of organoiodine reagents for the functionalizations and newlineconstruction of diverse five- and six-membered azaheterocycles. newlineThe first chapter briefly highlights structures and properties of organoiodine reagents. Up-to-date review of recent advances in the chemistry of organoiodine reagents, particularly in the construction of various natural and synthetic bioactive heterocycles has been provided in this chapter. newlineChapter two deals with the organoiodine-promoted synthesis of 1,3,4-oxadiazoles. The chapter is divided into two parts. Part A provides an efficient protocol for the preparation of and#945;-keto-1,3,4-oxadiazoles has been developed in good to excellent yield via the IBX-TEAB mediated oxidative cyclization of in-situ generated hydrazide-hydrazones prepared from the reaction of aryl glyoxal and hydrazides. Identified one-pot protocol is fairly general to prepare and#945;-keto-1,3,4-oxadiazoles in high yields and short reaction times. Part B of this chapter describes a facile one-pot and solvent-free synthesis of 2-arylamino-1,3,4-oxadiazoles. The methodology involves simple grinding of aryl hydrazides with arylthiosemicarbazides in presence of iodobenzene diacetate. The reaction proceeds through in situ formation of acyl thiosemicarbazides at room temperature. Highlights of the protocol are mild reaction conditions, use of easily accessible starting materials, solvent-free greener synthetic approach, simple work ups and excellent yields. newlineIn third chapter, copper-catalyzed direct C-H arylation of azaheterocycles including oxadiazoles, thiadiazoles, benzoxazoles and benzothiazoles has