Synthesis Of Chiral Jolunidine Derivatives Via Ru(Diamine)-Catalyzed Asymmetric Cascade Hydrogenation/Reductive Amination

Julolidine and their derivatives,as one of the important classes of hetero-polycyclic compounds,have attracted continued attention from the scientific community because of their many applications in photochemical industry as fluorescent dyes and also in biological systems.Over the past several decades,numerous strategies and methods have been developed for the synthesis of julolidine derivatives.However,the catalytic asymmetric synthesis of optically active julolidine derivatives is less studied.Therefore,the development of step-efficient asymmetric approaches for rapid and direct construction of structurally diverse chiral julolidine derivatives is highly desirable and still a big challenge.To address this issue and based on our research work on catalytic asymmetric hydrogenation of N-containing heteroarenes and asymmetric cascade recations,herein,this dissertation focuses on the asymmetric hydrogenation cascade reaction of nitrogen-containing aromatic heterocyclic compounds by using chiral Ru(diamine)catalytic system.The main research results are as follows:A direct and facile construction of optically pure jolunidine derivatives via ruthenium-catalyzed enantioselective cascade hydrogenation and reductive amination of4-(quinolin-8-yl)ketones has been developed.Using this protocol,various chiral julolidine compounds were obtained in high isolated yields with excellent diastereoselectivity(up to >20:1 dr)and enantioselectivity(up to 99% ee)under mild conditions.Furthermore,the synthetic practicality of this cascade strategy was further illustrated by a gram-scale reaction and the preparation of hexahydrojulolidine derivatives.A new luminogenic molecule derived from the resulting chiral julolidine derivative was synthesized and fully characterized.Its photophysical properties were characterized by UV-vis and fluorescence spectra.Our preliminary results indicated that this compound shows a significant aggregation-induced emission(AIE)phenomenon.