A STUDY ON HETEROCYCLIC SYNTHESIS VIA CYCLIZATION AS A KEY REACTION FROM HETERO ATOM-CONTAINING UNSATURATED COMPOUNDS

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1. Highly diastereoselective and enantioselective hetero Diels-Alder reactions of a variety of thiabutadienes such as thiochalcones, α, β-unsatturated dithioesters, α-arylmethylenethiotetralones, and alkyl-substituted and camphor-derived thiabutadienes with a chiral or achiral N-propenoyloxazolidinone dienophile, using chiral Lewis acids (e.g., copper triflate)-bis(oxazoline) and bis(imine) complex catalysts for the latter, have been developed. A homochiral cyclic sulfide derived from the cycloadduct catalyzed the enantioselective Corey-Chaykovsky epoxidation and aziridination of aldehydes and imines with halides in the presence of base.2. Stereoselective, diene-transmissive hetero Diets-Alder ractions of cross-conjugated heterotrienes (N, O, S) to give ringfused heterocycles have been developed. The azatrienes reacted for the initial cycloaddition with reactive dienophiles such as tosylisocyanates, ketenes and vinyl ethers, depending on the substituents on the azatrienes. The second cycloaddition underwent normal electron-demanding Diels-Alder reaction with a variety of dienophiles.3. Tandem cyclizations strategy of functionalized carbodiimides bearing an alkene, a Michael acceptor, a carboxy ester, an acetal or an epoxy ring, which were prepared by the aza-Wittig reaction of iminophosphoranes with isocyanates, have been developed for facile synthesis of a variety of ring-fused nitrogen-heterocyclic compounds such as imidazo-quinolines, imidazoimidazoles, imidazopyrimidines, imidazoquinazolines, imidazothiazines, pyrimidobenzothiazines, quinazolinobenzothiazines, and diazepinoquinolines. The method includes the initial annulation of an intramolecular amine-nucleophilic addition to the cumulene carbon, followed by the second cyclization of a newly formed amine by reacting with an inner functional group.