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SYNTHESIS OF NHETEROARYL SUBSTITUTED

CHAPTER ONE

1.1       INTRODUCTION

The basic sulphonamide group –SO2NH- occurs in various biological active compounds including antimicrobial drugs, antithyroid agents, antitumor antibiotics and inhibitors of carbonic anhydrase1,2.  Sulphonamides are widely used to treat microbial infection by inhibiting the growth of gram-negative and gram-positive bacteria, some protozoa and fungi3. Clinically, sulphonamides are used to treat several urinary tract infections and gastrointestinal infections4. Sulphonamides that are aromatic or hetroaromatic are responsible for the inhibition of the growth of tumor cells. They act as antitumor agents by inhibiting carbonic anhydrase. Sulphonamides are structurally similar to p-aminobenzoic acid (PABA) which is a cofactor that in needed by the bacteria for the synthesis of folic acid. Sulphonamides antibiotics inhibit the synthesis of purine and DNA in the microorganism. Sulphonamide antibiotics are used as veterinary medicines to treat infections in livestock herds5,6. Sulphonamides are extremely useful pharmaceutical compounds because they exhibit a wide range of biological activities such as anticancer, anti-inflammatory and antiviral functions7-11. The sulphonylation of amines with sulphonyl chlorides in the presence of a base is still being used as the method of choice because of high efficiency and simplicity of the reaction12. However, this approach is limited by the formation of undesired disulphonamides with primary amines and by the need of harsh reaction conditions for less nucleophilic amines such as anilines13. Additionally, side reactions take place in the presence of a base. Sulphonamides have been used as protecting groups of OH or NH functionalities for easy removal under mild conditions14-15. In recent years, molecular iodine has been extensively used for a plethora of organic transformations as an inexpensive, nontoxic, readily available catalyst under very mild and convenient conditions to afford the corresponding products in excellent yields with high selectivity16-22. This can be seen in the case of efficient molecular iodine catalyzed method developed for preparing sulphonamides (Scheme 1).

 

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