Investigation of ortho carboxylic acid effect in ullmann reaction of halothiophenes and halobenzenes

Abstract

The foundation of modern crosscoupling chemistry was built at the newlinebeginning of the twentieth century with the pioneering work of Fritz Ullmann newlineand Irma Goldberg Their explorations into new methods for the synthesis of newlinearyl CC CN and CO bonds provided the conceptual breakthrough that newlineallowed for the use of unactivated aryl halides to supplant the electronpoor newlinearyl halides typically required for the classical nucleophilic aromatic newlinesubstitution reaction Classical Ullmann and Goldberg protocols typically newlinerequire harsh conditions such as high temperature extended reaction time newlineand in some cases stoichiometric amount of copper The use of chelating newlineligands has provided the major driving force behind the evolution of Cucatalyzed newlinearyl C N and C O bondforming processes Copper I newlinethiophene2carboxylate in particular has been found to bring about the cross newlinecoupling very rapidly at ambient conditions The classical copper mediated newlineUllmann coupling provided a practical alternate to Pd mediated approach for newlinelarge scale synthesis newlineS urprisingly Ullmann cross coupling of aryl halides or heteroaryl newlinehalides with metal bisulphite or sulphite had received only scanty attention newlinedespite the fact that the resulting sodium or potassium salts of sulphonic acids newlinecan be useful precursors for sulphonamides some of which have been found newlineto exhibit useful biological activity Sulphonyl chlorides are also used for newlinederivatization and protection of primary and secondary amines With scanty newlinereferences in the literature specifically under aqueous conditions and high newlineutility of these classes of compounds it was of interest to explore the aromatic newlinenucleophilic substitution by sodium bisulphite using copper catalyst on newlineactivated aromatic and heteroaromatic halides newlineThe present thesis comprises of four chapters The first chapter deals newlinewith the introduction and review of earlier work reported in the literature newlinepertaining to each topic mentioned under the objectives The second chapter newlinedescribes the experimental procedures and analytical information newline