Recoverable and Recyclable Catalysts for Reduction of Azides and Asymmetric Organic Transformations

Pagoti, Sreenivasarao (2016) Recoverable and Recyclable Catalysts for Reduction of Azides and Asymmetric Organic Transformations. PhD thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

The present work starts with a description the reduction of a broad range of organic azides to the corresponding amines using hydrazine hydrate as the hydrogen source in the presence of reusable Fe3O4-MNPs in aqueous medium. This chapter demonstrates the scope and limitations for the aromatic or heteroaromatic azides with both electron rich and deficient functional groups to give the corresponding amine products in high yields. It then discusses a modular synthetic approach for the synthesis of a new magnetic chiral imidazolidinone catalyst using Cu(I)-catalyzed Huisgene cycloaddition which was used for the first time for an asymmetric 1,3 dipolar cycloaddition of various nitrones with α,β-unsaturated aldehydes. The desired isoxazolidines were obtained in high yields with excellent endo diastereoselectivity and enantioselectivity. Moreover the catalyst could be magnetically recovered and recycled for four times without any significant loss in yields and enantioselectivities of the endo adducts. Thereafter it explores different strategies for the preparation of supported chiral tbutyl imidazolidinones using MNP and polystyrene support for Friedel-Crafts alkylation of indoles with α,β-unsaturated aldehydes. The corresponding adducts were obtained in high yields and enantioselectivities. The MNP-catalyst was recycled and reused for five consecutive runs without observing significant loss in yields and enantioselectivities of the products. It concludes by describing the synthesis of ionic tagged chiral tbutyl imidazolidinones. The synthesised catalysts were used for the Friedel-Crafts alkylation of indoles with the α,β-unsaturated aldehydes. The corresponding adducts were obtained in high yields and enantioselectivities. Moreover, the catalyst was recycled and reused for five consecutive runs maintaining the same catalytic activity and selectivity.

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