Suman Srivastava

Natural Product Inspired Diversity Oriented Synthesis of Tetrahydroquinoline Scaffolds as Antitubercular Agent

An efficient natural product inspired diversity oriented syn thesis of tetrahydroquinoline analogues has been developed using the natural carbohydrate derived solid acid catalyst via multicomponent aza-Diels-Alder reaction of imine (generated in situ from aromatic amine and aldehyde) with dienophile in acetonitrile in a diastereoselective manner. The use of water as solvent reverses the diastereoselectivity toward the cis isomer. Interestingly, tricyclic pyrano/furano benzopyran with cis diastereoselectivity is obtained when salicylaldehyde is used as an alternative of aromatic aldehyde under the same condition. These synthesized quinolines and benzopyrans analogues have been evaluated for their Antitubercular activity against M. tuberculosis H₃₇Ra, and M. tuberculosis H₃₇Rv, and some of the analogues shows better activity profile than their natural product analogues. The protocol is not only mild, efficient, ecofriendly, but also involves reusable and biodegradable catalyst and provides route for both the diastereoisomer.

Synthesis of New Class of Alkyl Azarene Pyridinium Zwitterions via Iodine Mediated sp3 C–H Bond Activation

An efficient and conceptually different approach toward C-H bond activation by using iodine mediated sp(3) C-H functionalization for the synthesis of alkyl azaarene pyridinium zwitterions is described. This work has the interesting distinction of being the first synthesis of a new class of alkyl azaarene pyridinium zwitterion via transition-metal-free sp(3) C-H bond activation of an alkyl azaarene.

Functional ionic liquid mediated synthesis (FILMS) of dihydrothiophenes and tacrine derivatives

Natural amino acid-based functional ionic liquid [Bz-His(n-propyl)2-OMe+Br−] promoted diastereoselective synthesis of dihydrothiophenes is described. Further this functional ionic liquid was efficiently utilized to form tacrine derivatives from dihydrothiophenes using microwave irradiation. The functional ionic liquid exhibits organocatalytic as well as medium engineering capability, thus we named this synthetic protocol functional ionic liquid mediated synthesis (FILMS).

Diversity oriented synthesis of pyrrolidines via natural carbohydrate solid acid catalyst.

Natural carbohydrate scaffold catalyzed diastereoselective synthesis of functionalized pyrrolidines have been developed via 1,3-dipolar cycloaddition of azomethine ylides derived from alpha-imino esters with dienes or dipolarophiles. Naturally most abundant carbohydrates, like cellulose and starch, were converted into their sulfuric acid derivative, which are exhibiting efficient catalytic properties, along with excellent cost effectivity and recyclability. The advantages of this methodology are diversity oriented metal free synthesis of functionalized pyrrolidines, mild reaction condition, high diasteroselectivity and yield.

Cascade [4 + 1] annulation via more environmentally friendly nitrogen ylides in water: synthesis of bicyclic and tricyclic fused dihydrofurans

A novel imidazolium ylide activated [4 + 1] annulation approach is described for the diastereoselective synthesis of bicyclic and tricyclic fused dihydrofurans in water. This cascade annulation presumably proceeds via a Michael reaction triggered zwitterion enolate followed by concomitant intramolecular cyclization. The methodology has distinction of being the first report on imidazolium ylide mediated [4 + 1] annulation in water as a unified greener approach involving an in situ base regeneration system and an alternative to pyridine ylide.

A novel access to indole-3-substituted dihydrocoumarins in artificial sweetener saccharin based functional ionic liquids

An efficient new multicomponent protocol for the C-3 functionalization of indoles with dihydrocoumarin has been developed using an artificial sweetener (saccharin)-based functional ionic liquid (imidazolium saccharinate). The reaction consists of the Knoevenagel coupling of salicylaldehyde and Meldrums acid followed by a Michael type reaction with indole, resulting in concomitant lactonization via decarboxylative elimination to yield indole-3-dihydro-coumarins in good to excellent yields at room temperature.

Functional ionic liquid [bmim][Sac] mediated synthesis of ferrocenyl thiopropanones via the “dual activation of the substrate by the ionic liquid”

An artificial sweetener saccharin based functional ionic liquid [bmim][Sac] mediated synthesis has been explored for the first time in the organometallic field. The ionic liquid plays a critical role as the catalyst for substrate activation by directly facilitating the “solvent-free” Michael addition of thiol to ferrocenyl enone. The key to the present methodology is the dual hydrogen bonding of the saccharinate anion that is believed to play a crucial role in thiol activation. All the synthesized ferrocene thiopropanones were examined for their in vitro anti-proliferative activity.

Novel diastereoselective synthesis of spiropyrrolidine-oxindole derivatives as anti-breast cancer agents

A novel class of diastereoselective spiropyrrolidine-oxindole derivatives were synthesized from isatin, 2-phenylthiazolidine-4-carboxylic acid and chalcone in a one-pot multicomponent reaction via 1,3-dipolar cycloaddition. The advantages of this methodology are the mild reaction conditions, high diastereoselectivity and high yield. These derivatives exhibited promising anti-cancer activity against the human breast cancer cell lines.