Hydrogen Bond Donor-Catalyzed One-Pot Transformations of 2,2-Disubstituted Epoxides: Synthesis of Functionalized Nitrile-Rich Derivatives.

A practically intriguing catalytic domino methodology has been developed for the synthesis of highly functionalized pyran and ethene-1,1,2-tricarbonitrile derivatives in a single-pot operation. The -dicyano olefins and the corresponding epoxide were taken as the reactive partners in the presence of a hydrogen bond donor (HBD)-catalyzed condition. The reaction was found to be highly efficient in terms of the formation of sequential C-C and O-C bonds along with an exceptional C-C coupling step through a metal-free organocatalytic pathway.

Structural and Synthetic Aspects of Small Ring Oxa- and Aza-Heterocyclic Ring Systems as Antiviral Activities.

Antiviral properties of different oxa- and aza-heterocycles are identified and properly correlated with their structural features and discussed in this review article. The primary objective is to explore the activity of such ring systems as antiviral agents, as well as their synthetic routes and biological significance. Eventually, the (SAR) of the heterocyclic compounds, along with their salient characteristics are exhibited to build a suitable platform for medicinal chemists and biotechnologists.

Synthesis of Functionalized Five-Membered Heterocycles from Epoxides: A Hydrogen-Bond Donor Catalytic Approach.

The synthesis of highly functionalized five-membered oxa- and aza-heterocycles has been reported utilizing hydrogen-bond donor (HBD) catalysis. In this method, an epoxide was taken as a substrate and reacted with functionalized arylidene/alkylidene malononitrile derivatives in the presence of a newly designed HBD catalyst. In all the cases, the products 2,5-disubstituted tetrahydrofurans (2,5-THFs) were obtained in good to excellent yields (up to 86%) with high diastereoselectivity (dr up to 99:1) as a single regioisomer.

Domino Michael-Michael and Aldol-Aldol Reactions: Diastereoselective Synthesis of Functionalized Cyclohexanone Derivatives Containing Quaternary Carbon Center.

A simple strategy for the synthesis of highly functionalized cyclohexanone derivatives containing an all-carbon quaternary center from α-(aryl/alkyl)methylidene-β-keto esters or β-diketones via a K-enolate mediated domino Michael-Michael reaction sequence with moderate to good yield and excellent diastereoselectivity (de > 99%) is described. Interestingly, Li-base mediated reaction of α-arylmethylidene-β-diketones affords functionalized 3,5-dihydroxy cyclohexane derivatives as the kinetically controlled products via a domino aldol-aldol reaction sequence with excellent diastereoselectivity. Li-enolates of the β-keto esters or β-diketones undergo facile domino Michael-Michael reaction with nitro-olefins to afford the corresponding nitrocyclohexane derivatives in good yields and excellent diastereoselectivity (de > 99%).

A new pyrene based highly sensitive fluorescence probe for copper(II) and fluoride with living cell application.

A new pyrene based fluorescence probe has been synthesized for fluorogenic detection of Cu(2+) in acetonitrile-aqueous media (7 : 3 CH3CN-HEPES buffer, v/v, at pH 7.5) with bioimaging in both prokaryotic (Candida albicans cells) and eukaryotic (Tecoma stans pollen cells) living cells. The anion recognition properties of the sensor have also been studied in acetonitrile by fluorescence methods which show remarkable sensitivity toward fluoride over other anions examined.

Hydroxylated HMPA enhances both reduction potential and proton donation in SmI₂ reactions.

HMPA is known to increase the reduction potential of SmI2. However, in many cases, the transferred electron returns from the radical anion of the substrate back to the Sm(3+). This could be avoided by an efficient trapping of the radical anion: e.

A highly selective and sensitive probe for colorimetric and fluorogenic detection of Cd2+ in aqueous media.

A new rhodamine-quinoline based dyad has been synthesized. It shows a highly selective response to Cd(2+) in the presence of other competing metal ions in aqueous media (pH = 7.1).

Memory of chirality (MOC) concept in imino-aldol reaction: enantioselective synthesis of α,β-diamino esters and aziridines.

A simple strategy for the synthesis of chiral α,β-diamino- and α-amino,β-hydroxy ester derivatives in high yields with moderate to high ee has been developed via asymmetric imino-aldol and aldol reactions, respectively, starting from protected aminoesters employing memory of chirality concept for chiral induction. This strategy has been extended for the enantioselective synthesis of aziridines (ee up to 92%). The absolute configuration of the imino-aldol adducts has been determined.

Domino imino-aldol-aza-Michael reaction: one-pot diastereo- and enantioselective synthesis of piperidines.

Addition of α-arylmethylidene- or α-alkylidene-β-keto ester enolate to N-activated aldimines via the imino aldol pathway followed by intramolecular aza-Michael reaction in a domino fashion has been developed, and a highly diastereoselective route to substituted piperidines is reported. Enantiopure piperidines are synthesized from chiral sulfinyl imines. Formation and the observed stereoselectivity of the products have been rationalized by mechanistic and computational studies.