Amit Saha

A simple and facile Heck-type arylation of alkenes with diaryliodonium salts using magnetically recoverable Pd-catalyst

The Heck-type arylation of alkenes was achieved in aqueous polyethylene glycol using a magnetically recoverable heterogenized palladium catalyst employing diaryliodonium salts under ambient conditions. The benign reaction medium and the stability of the catalyst are the salient features of this simple and facile protocol.

Remarkable influence of substituent in ionic liquid in control of reaction: simple, efficient and hazardous organic solvent free procedure for the synthesis of 2-aryl benzimidazoles promoted by ionic liquid, [pmim]BF4

A simple and efficient procedure for the synthesis of 2-substituted benzimidazoles has been developed by a one-pot reaction of o-phenylenediamine with aromatic aldehydes in the presence of an ionic liquid, 1-methyl-3-pentylimidazolium tetrafluoroborate, [pmim]BF4 at room temperature in open air without any organic solvent. The ionic liquid is recycled. A remarkable influence of the substituent on the imidazolium unit of the ionic liquid on the outcome of the reaction is observed.

One-pot copper nanoparticle-catalyzed synthesis of S-aryl- and S-vinyl dithiocarbamates in water: high diastereoselectivity achieved for vinyl dithiocarbamates

A convenient, green and efficient procedure for the synthesis of aryl and vinyl dithiocarbamates has been developed by a simple one-pot three component condensation of an amine, carbon disulfide, and an aryl iodide or a styrenyl bromide catalyzed by copper nanoparticles in water. Significantly, the (E)- and (Z)-styrenyl bromides provide the corresponding (E)- and (Z)-styrenyl dithiocarbamates in high diastereoselectivities. The catalyst is recycled.

O-Allylation of phenols with allylic acetates in aqueous media using a magnetically separable catalytic system

Allylic ethers were synthesized in water using magnetically recoverable heterogeneous Pd catalystvia O-allylation of phenols with allylic acetates under ambient conditions. The aqueous reaction medium, easy recovery of the catalyst using an external magnet, efficient recycling, and the high stability of the catalyst renders the protocol economic and sustainable.

Inside-out core–shell architecture: controllable fabrication of Cu2O@Cu with high activity for the Sonogashira coupling reaction

Inside-out core-shell architectures (Cu(2)O@Cu) with a Cu(2)O core and a Cu shell, which are in contrast to the normally reported Cu(2)O-outside structure (Cu@Cu(2)O), were fabricated. This strategy can also be applied to construct square and hexapod Cu(2)O@Cu. The obtained Cu(2)O@Cu composite exhibits excellent catalytic activity for the Sonogashira coupling reactions.

Metal nanoparticles as efficient catalysts for organic reactions

Pd(0) nanoparticles have been demonstrated to be very efficient catalysts for C–C bond-forming reactions. These include coupling of vicinal-diiodoalkenes and acrylic esters and nitriles leading to the stereoselective synthesis of 2-alkene-4-yn-esters and nitriles, allylation of active methylene compounds by allyl acetate, and Hiyama cross-coupling of aryliodides with arylsilanes. Cu(0) nanoparticles catalyze aryl-sulfur bond formation, accomplishing the synthesis of functionalized aryl sulfides and aryl- and vinyl dithiocarbamates. Cu nanoparticles have also been used for the chemoselective reduction of aromatic nitro compounds.

A modular synthesis of dithiocarbamate pendant unnatural α-amino acids

Unnatural α-amino acids containing dithiocarbamate side chains were synthesized by a one-pot reaction of in situ generated dithiocarbamate anions with sulfamidates. A wide range of these anions participated in the highly regio- and stereo-selective ring opening of sulfamidates to produce the corresponding dithiocarbamate pendant α-amino acids in high yields.

Ruthenium(III)-catalysed phenylselenylation of allyl acetates by diphenyl diselenide and indium(I) bromide in neat: isolation and identification of intermediate

A fast and efficient phenylselenylation of allyl acetates by diphenyl diselenide and indium(I) bromide has been achieved in neat under the catalysis of Ru(acac)(3). The intermediate complex of diphenyl diselenide and indium has been isolated and identified as a polymeric pentacoordinated In(III) selenolate complex, [In(SePh)(3)](n).

Mechanism of Inducible Nitric-Oxide Synthase Dimerization Inhibition by Novel Pyrimidine Imidazoles

Background: Overproduction of nitric oxide by dimeric inducible nitric-oxide synthase (iNOS) is physiologically harmful. Results: Pyrimidine imidazole derivative (PID) binds to both the iNOS dimer and monomer causing irreversible monomerization and inhibition of dimerization, respectively. Conclusion: PID can physiologically inhibit iNOS both during and after its assembly into active enzyme. Significance: Our study reveals PIDs dual ability to inhibit iNOS as well as their kinetic mechanisms. Overproduction of nitric oxide (NO) by inducible nitric-oxide synthase (iNOS) has been etiologically linked to several inflammatory, immunological, and neurodegenerative diseases. As dimerization of NOS is required for its activity, several dimerization inhibitors, including pyrimidine imidazoles, are being evaluated for therapeutic inhibition of iNOS. However, the precise mechanism of their action is still unclear. Here, we examined the mechanism of iNOS inhibition by a pyrimidine imidazole core compound and its derivative (PID), having low cellular toxicity and high affinity for iNOS, using rapid stopped-flow kinetic, gel filtration, and spectrophotometric analysis. PID bound to iNOS heme to generate an irreversible PID-iNOS monomer complex that could not be converted to active dimers by tetrahydrobiopterin (H4B) and l-arginine (Arg). We utilized the iNOS oxygenase domain (iNOSoxy) and two monomeric mutants whose dimerization could be induced (K82AiNOSoxy) or not induced (D92AiNOSoxy) with H4B to elucidate the kinetics of PID binding to the iNOS monomer and dimer. We observed that the apparent PID affinity for the monomer was 11 times higher than the dimer. PID binding rate was also sensitive to H4B and Arg site occupancy. PID could also interact with nascent iNOS monomers in iNOS-synthesizing RAW cells, to prevent their post-translational dimerization, and it also caused irreversible monomerization of active iNOS dimers thereby accomplishing complete physiological inhibition of iNOS. Thus, our study establishes PID as a versatile iNOS inhibitor and therefore a potential in vivo tool for examining the causal role of iNOS in diseases associated with its overexpression as well as therapeutic control of such diseases.

Ruthenium catalysed one-pot synthesis of S-allyl and cinnamyl dithiocarbamates using allyl and cinnamyl acetates in water

A convenient and efficient procedure for the synthesis of S-allyl/cinnamyl dithiocarbamates has been developed by a one-pot reaction of allyl/cinnamyl acetate, carbon disulfide and amine in presence of Ru(acac)3 in water. A variety of functionalized dithiocarbamates have been obtained by this procedure in high yields. The reaction proceeds via a catalytic Ru(II) species, generated in situ during the reaction.