New synthetic methods in organic chemistry

Abstract

Synthetic organic chemistry has witnessed exponential growth in recent years due to the discovery of new synthons, reagents, principles and concepts, Suitable functionalisation of carbonyl groups, for example, can cause a reversal of the usual polarization, which has been exploited in a variety of ways, the synthesis of cis-Jammone being one such application. Double insertions of carbenes generated from carbon tetrabromide and methyl lithium can aid the elaboration of complex molecules such as Ishwarane. Acid or base treatment of lactams and lactones with pendant alcohol or amine side chains can lead to very large rings in a thermodynamic cally favoured ring expansion. The inacrocyclic lactone, carpaine arises from one such reaction, while kapa {potassium aminopropylamide) brings about the zipper reaction leading to macrocyclic lactams. Dimsyl anion and nitromethane have been used as synthons in reactions with isatoic anhydride to afford new synthesis of indigo, which has also become available in two steps from styrene oxide by nitration and reduction. The use of crown ethers for solubilisation of inorganic salts has enormously facilitated reactions like nucleophilic displacement and oxidation in organic chemistry. Reactions with many promising industrial applications have become available with the advent of new inorganic reagents, benzene for instance, being acetoxy-methylated by tellurium dioxide and acetic acid. Liquid paraffin appears to have good potential in the economic reduction of nitroaromatics. Cycloaddition reactions of acetylenedicarboxylic esters to a variety of dinucleo-philes offer efficient synthesis of large variety of heterocycles. The use of synthons such as mono or diaminonitroethylene has resulted in the direct construction of nitroheterocycles. Photosynthesis has achieved industrial prominence, as evidenced by the large scale manufacture of lauryl or caprolactam (nylon monomers) by photo nitrosation of alicyclic ketones. Simple petrochemicals can be efficiently used for a variety of synthesis including many drugs. The construction of the sintamil molecules from o-aminophenol and o-chlorobenzoic acid will-be one of the several examples cited.