Catalytic Synthesis of Branched Ketones, and N-Heteroaromatic Compounds Using Acceptorless Dehydrogenative Coupling and Hydrogen Transfer Strategies
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The present thesis, entitled as “Catalytic Synthesis of Branched Ketones, and N-Heteroaromatic Compounds Using Acceptorless Dehydrogenative Coupling and Hydrogen Transfer Strategies” is divided into six chapter based on the obtained results of experimental works performed during the complete course of the PhD research period. Chapter-1 includes a brief introduction about the basic concepts of acceptorless dehydrogenation, borrowing hydrogen catalysis via metal-ligand cooperation, and a general background of transfer hydrogenation reactions. Chapter-2 reports the synthesis and characterization of new phosphine-free triazine-based NNN pincer ligands and their ruthenium (III) complexes and its application in the catalytic synthesis of β-branched ketones via α-alkylation of ketones using secondary alcohols. Chapter-3 demonstrates catalytic cross-coupling of primary and secondary alcohols to α–substituted ketones and two different secondary alcohols to β–disubstituted ketones with good to excellent yield under aerobic condition with catalytic amount of base and high selectivity in the C-C bond formation. Chapter-4 describes an atom-economic acceptorless dehydrogenative coupling of alcohols using a simple phosphine-free Ru(III) complex with low catalyst and base loading under aerial condition to form a wide variety of substituted quinolines and quinazolines in moderate to good yields. Chapter-5 reports boric acid-catalyzed chemoselective reduction of quinolines to synthetically versatile 1,2,3,4-tetrahydroquinolines under mild reaction conditions using Hantzsch ester as an organic hydrogen source. The synthetic utility of the present protocol was explored towards several bioactive molecules. Chapter-6 illustrates arylboronic acid-catalyzed one-pot reduction of quinoline to N-arylated tetrahydroquinoline by external base-free Chan-Lam-Evans amination under air. The methodology proved to be useful alternative for the construction of bio-relevant N-heterocycles.
Supervisor: Animesh Das