Study of Intramolecular C-N, C-O and C-S Cross-Coupling Reactions and Application of Self-Assembled Chiral Copper(II) Complexes for Asymmetric Acylation Reaction

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The thesis contains four chapters. The first three chapters describe the synthesis of 2- substituted benzimidazoles, benzoxazoles and benzothiazoles by intramolecular C-N, C-O and C-S cross-coupling reactions using CuO nanoparticles as a recyclable catalyst. The fourth chapter describes the synthesis of self-assembled chiral copper(II) complexes and their application for the asymmetric acylation of secondary alcohols. Chapter I. CuO Nanoparticles Catalyzed Intramolecular CDN Cross- Coupling Reaction: Synthesis of 2-Substituted Benzimidazoles Benzimidazoles are privileged organic compounds due to their recognition in biological and therapeutic activities. This chapter describes CuO nanoparticles catalyzed synthesis of 2-substituted benzimidazoles from 2-bromoarylamidines and 2-bromoarylguanidines by intramolecular CDN cross-coupling reactions (Scheme 1). A variety of substrates undergo reactions to give the target products in high yield. The procedure is general and the catalyst is recyclable without loss of activity. N R2 HN R3 N N R2 5 mol % CuO nanoparticles 2.0 equiv KOH/K2CO3 X X = Br, I R1 = H, Br, Cl, Me, OMe R2 = Me, phenyl R3 R3 = alkyl, aryl, Bn DMSO,110 DC R1 R1 upto 96% yield Scheme 1 Chapter II. CuO Nanoparticles Catalyzed Intramolecular CDO Cross- Coupling Reaction: Synthesis of 2-Alkyl and 2-Arylbenzoxazoles Benzoxazoles are an important structural motif found in wide range of natural products and therapeutically active agents. This chapter focuses on the synthesis of 2-substituted benzoxazoles from 2-haloarylamides using CuO nanoparticles (Scheme 2). The substrates undergo intramolecular CDO cross-coupling reaction in presence of 5 mol % CuO nanoparticles and 1.5 equiv of K2CO3 or Cs2CO3 at 110 DC to give the corresponding 2- aryl or alkylbenzoxazoles in high yield. The reactions are simple, general and the catalyst can be recovered and recycled without loss of activity and selectivity..
Supervisor: T. Punniyamourthy