Application of Branching Double Annulation Cascade (BDAC) and Ring Opening Cyclization (ROC) Strategies: Access to Diverse fused Tetrahydroisoquinoline, Quinazolinone derivatives and Rutaecarpine Alkaloid

Nitrogen-containing compounds are the most common structural architectures in drug candidates, natural and biological products, and small-molecule therapeutics. Nheterocyclic containing natural product synthesis has been a very challenging area due to the structural complexity inherent in these molecules. The nitrogen atoms contained in these molecules are essential for their biological activity, as nitrogen can hold a positive charge as well as act as both hydrogen-bond donor and hydrogen-bond acceptor. These features are significant for the interaction between medicinal agents and their molecular targets. Although synthetic chemists have long been fascinated by natural products, for the most part they have focused on developing the chemistry in order to make precise replicates of the compounds purified from natural sources. Recently, synthetic targets concerning natural products have not been limited to precise replication of the naturally occurring compounds. The accumulation of insights and learning in total synthesis over the last few decades should enable organic chemists to “aim higher” to integrate natural products more closely with advance in biomedical research. Today, chemists can develop synthetic strategies to make both natural products and natural product-like compounds that are comparable to true natural products in size and complexity. The ability to synthesize in vitro complex natural products, combined with strategy of diversity-oriented synthesis (DOS) of natural product-like molecules, which allows very large numbers of natural product-based compound libraries to be made quickly, has made it possible for chemists to accelerate evolution in vitro in this process. Herein, we report a novel BDAC strategy for rapid access to diverse molecular library containing unprecedented THIQ fused skeletons by using 2-(2-bromoethyl)benzaldehyde 19 as a common substrate and variety of N,C-, N,O- and N,N-1,5-bisnucleophiles as SBAs. Apart from that we also successfully developed a facile methodology for Copper-catalyzed intramolecular α-C‒H amination via ring-opening cyclization strategy to quinazolin-4-one derivatives and application in Rutaecarpine synthesis

Scaffold Diversity through a Branching Double Annulation Cascade Strategy: An Iminium Induced One-pot Synthesis of Diverse Fused Tetrahydroisoquinoline (THIQ) Scaffolds

A branching double annulation cascade (BDAC) strategy for diverse and complex fused THIQ scaffolds via a highly reactive iminium induced one-pot double cyclization sequence involving Pictect-Spengler type cyclization has been developed for the first time. The salient features of this protocol are direct and rapid access to unprecedented diverse fused THIQ skeletons, metal/catalyst free, cleaner reaction profile, good to excellent yields and convenient approach. This catalyst-free domino process facilitates the double annulation with variety of scaffold building agents via two C-N and one C-X (X = C, N, O) bonds formation in a single step, under uniform reaction conditions. Furthermore, we reveal an unusual dual BDAC sequence leading to N-N linked isoquinoline dimer

A highly efficient synthesis of imidazo-fused polyheterocycles via Groebke–Blackburn–Bienaymè reaction catalyzed by LaCl3·7H2O

A highly efficient and mild protocol for the synthesis of imidazo-fused polyheterocycles via Groebke–Blackburn–Bienaymè reaction under the influence of catalytic amount of lanthanum chloride heptahydrate has been described. A wide range of nitrogen-enriched polyheterocycles are synthesized with high yields under neat conditions

A facile one-pot protocol for the synthesis of tetrazolyl-tetrahydroisoquinolines via novel domino intramolecular cyclization/Ugi-azide sequence

A facile one-pot, four-component domino reaction between 2-(2-bromoethyl)benzaldehyde, isocyanide, amine, and azide for the synthesis of tetrazolyl-tetrahydroisoquinoline derivatives has been developed. The reaction sequence involves intramolecular replacement of halide by iminium nitrogen followed by Ugi-azide reaction. The reaction is catalyst/additive free and takes place under ambient conditions with short reaction times to furnish products in good to excellent yields

Design and Synthesis of Novel Indole and Carbazole Based Organic Dyes for Dye Sensitized Solar Cells: Theoretical Studies by DFT/TDDFT

We herein report the design and synthesis of three new indole and carbazole based dyes (D1, D2 and D3) with a donor-(π-spacer)-acceptor (D-π-A) configuration with N-methylindole and carbazole as donors, barbituric acid and N-acyloxindole as acceptors/anchoring groups. DFT calculations of three dyes D1, D2 and D3 by using the B3LYP/6-31+G(d) basis set provided the optimized ground-state molecular geometries. Theoretical light harvesting efficiencies (LHE), of all the dyes were studied by time dependent density functional theory (TD-DFT) method in order to shed the light on how the π-conjugation order influence the performance of the dyes. Along with the TD-DFT calculations photophysical and electrochemical properties of the dyes were investigated by UV spectroscopy and cyclic voltammetry (CV), which indicates that D3 could show the best performance among the three dye