Project description:A copper-catalyzed domino reaction between itaconate esters and diethyl zinc (or silane) is developed, affording itaconate dimerization products, multi-ester-substituted cyclopentanones, in moderate to high yields.
Project description:Despite major advances in T cell receptor (TCR) biology and structure, how peptide-MHC complex (pMHC) ligands trigger ?? TCR activation remains unresolved. Two views exist. One model postulates that monomeric TCR-pMHC ligation events are sufficient while a second proposes that TCR-TCR dimerization in cis via C? domain interaction plus pMHC binding is critical. We scrutinized 22 known TCR/pMHC complex crystal structures, and did not find any predicted molecular C?-C? contacts in these crystals that would allow for physiological TCR dimerization. Moreover, the presence of conserved glycan adducts on the outer face of the C? domain preclude the hypothesized TCR dimerization through the C? domain. Observed functional consequences of C? mutations are likely indirect, with TCR microclusters at the immunological synapse driven by TCR transmembrane/cytoplasmic interactions via signaling molecules, scaffold proteins, and/or cytoskeletal elements.
Project description:Orthogonal self-assembly represents a useful methodology to construct supramolecular polymers with AA- and AB-type monomers, as commonly used for covalently linked polymers. So far, the design of such monomers has relied heavily on three-dimensional macrocycles, and the use of two-dimensional shape-persistent macrocycles for this purpose remains rather rare. Here, we demonstrate a dimerization motif based on a hydrogen-bonded macrocycle that can be effectively applied to form orthogonal supramolecular polymers. The macrocycle-mediated connectivity was confirmed by single-crystal X-ray diffraction, which revealed a unique 2:2 binding motif between host and guest, bridged by two cationic pyridinium end groups through π-stacking interactions and other cooperative intermolecular forces. Zinc ion-induced coordination with the macrocycle and a terpyridinium derivative enabled orthogonal polymerization, as revealed by 1H NMR, DLS, and TEM techniques. In addition, viscosity measurements showed a transition from oligomers to polymers at the critical polymerization concentration of 17 μM. These polymers were highly concentration-dependent. Establishing this new dimerization motif with shape-persistent H-bonded macrocycles widens the scope of noncovalent building blocks for supramolecular polymers and augurs well for the future development of functional materials.
Project description:A nickel-catalyzed reductive dimerization of bromocyclobutenes to produce unusual and unprecedented cyclobutene dimers was developed. In a stereoconvergent procedure, various bromocyclobutenes were readily dimerized in good yields, with good diastereoselectivities and broad functional group tolerance. Notably, the presence of a carbonyl group in the starting material appears to dictate diastereoselectivity.
Project description:We report the synthesis of a tellurophene-containing low-bandgap polymer, PDPPTe2T, by microwave-assisted palladium-catalyzed ipso-arylative polymerization of 2,5-bis[(α-hydroxy-α,α-diphenyl)methyl]tellurophene with a diketopyrrolopyrrole (DPP) monomer. Compared with the corresponding thiophene analog, PDPPTe2T absorbs light of longer wavelengths and has a smaller bandgap. Bulk heterojunction solar cells prepared from PDPPTe2T and PC71 BM show PCE values of up to 4.4%. External quantum efficiency measurements show that PDPPTe2T produces photocurrent at wavelengths up to 1 µm. DFT calculations suggest that the atomic substitution from sulfur to tellurium increases electronic coupling to decrease the length of the carbon-carbon bonds between the tellurophene and thiophene rings, which results in the red-shift in absorption upon substitution of tellurium for sulfur.
Project description:A gold-catalyzed regioselective homodimerization of aliphatic terminal alkynes is described. Bulky and less Lewis acidic tBuXPhosAuNTf(2) is the preferred catalyst, and the additive, anhydrous NaOAc, substantially facilitates the reaction.
Project description:The first C5 polymerization is reported, where the main-chain is growing by five carbon atoms of the monomer at a time. Three dienyltriphenylarsonium ylide monomers were synthesized and polymerized with triethylborane as an initiator, leading to random terpolymers (C1, C3, C5) with mainly C5 repeating units (up to 84.1 %). It has been found that the methyl group (electron-donating substituent) on the conjugated double bond of the ylides facilitates the formation of C5 segments. A mechanism was proposed based on NMR characterization and DFT calculations. The high C5 content ensures that things are on the right track for pure C5 homopolymerization.
Project description:Inflammation, a characteristic physiological response to infections and tissue damage, commences with processes involving tissue repair and pathogen elimination, contributing to the restoration of homeostasis at affected sites. Hence, this study presents a comprehensive analysis addressing diverse aspects associated with this phenomenon. The investigation encompasses the synthesis, spectral characterizations (FT-IR, 1H NMR, and 13C NMR), and molecular modeling of p-phenylenediamine-phenylhydrazine-formaldehyde terpolymer (PPHF), a potent agent in promoting inflammation. To explore the reactivity, bonding nature, and spectroscopy, as well as perform molecular docking for in-silico biological evaluation, density functional theory (DFT) utilizing the def2svp/B3LYP-D3BJ method was employed. The results reveal significant biological activity of the tested compound in relation to anti-inflammatory proteins, specifically 6JD8, 5TKB, and 4CYF. Notably, upon interaction between PPHF and 6JD8, a binding affinity of -4.5 kcal/mol was observed. Likewise, the interaction with 5TKB demonstrated an affinity of -7.8 kcal/mol. Furthermore, a bonding affinity of -8.1 kcal/mol was observed for the interaction with 4CYF. Importantly, these values closely correspond to those obtained from the interaction between the proteins and the standard drug ibuprofen (IBF), which exhibited binding affinities of -5.9 kcal/mol, -7.0 kcal/mol, and -6.1 kcal/mol, respectively. Thus, these results provide compelling evidence affirming the tremendous potential of p-phenylenediamine-phenylhydrazine-formaldehyde (PPHF) as a highly promising anti-inflammatory agent, owing to the presence of nitrogen-a heteroatom within the compound.
Project description:A number of first-row transition metal salts catalyze deprotonative dimerization of acidic arenes. Under the atmosphere of oxygen, nickel, manganese, cobalt, and iron chlorides have been shown to dimerize five- and six-membered ring heterocycles as well as electron-poor arenes. Both tetramethylpiperidide and dicyclohexylamide bases can be employed; however, the former afford slightly higher yields.
Project description:A general method for a highly regioselective copper-catalyzed cross-coupling of two aromatic compounds using iodine as an oxidant has been developed. The reactions involve an initial iodination of one arene followed by arylation of the most acidic C-H bond of the other coupling component. Cross-coupling of electron-rich arenes, electron-poor arenes, and five- and six-membered heterocycles is possible in many combinations. Typically, a 1/1.5 to 1/3 ratio of coupling components is used, in contrast to existing methodology that often employs a large excess of one of the arenes. Common functionalities such as ester, ketone, aldehyde, ether, nitrile, nitro, and amine are well-tolerated.