Transient Metallo-Lipidoid Assemblies Amplify Covalent Catalysis of Aqueous and Non-Aqueous Reactions

Dissipative supramolecular assemblies are hallmarks of living systems, contributing to their complex, dynamic structures and emerging functions. Living cells can spatiotemporally control diverse biochemical reactions in membrane compartments and condensates, regulating metabolite levels, signal transduction or remodeling of the cytoskeleton. Herein, we constructed membranous compartments using self-assembly of lipid-like amphiphiles (lipidoid) in aqueous medium. The new double-tailed lipidoid features Cu(II) coordinated with a tetravalent chelator that dictates the binding of two amphiphilic ligands in cis-orientation. Hydrophobic interactions between the lipidoids coupled with intermolecular hydrogen bonding led to a well-defined bilayer vesicle structure. Oil-soluble S_NAr reaction is efficiently upregulated in the hydrophobic cavity, acting as a catalytic crucible. The modular system allows easy incorporation of exposed primary amine groups, which augments the catalysis of retro aldol and C−N bond formation reactions. Moreover, a higher-affinity chelator enables consumption of the Cu(II) template leveraging the differential thermodynamic stability, which allows a controllable lifetime of the vesicular assemblies. Concomitant temporal upregulation of the catalytic reactions could be tuned by the metal ion concentration. This work offers new possibilities for metal ion-mediated dynamic supramolecular systems, opening up a massive repertoire of functionally active dynamic “life-like” materials.     

Unconditionally-secure key pre-distribution for triangular grid based wireless sensor network

We present an unconditionally-secure key pre-distribution scheme for a wireless sensor network using t-degree bivariate polynomials. The proposed scheme is proven to be perfectly resilient against both node disconnection and link failure. The memory requirements, computation and communication overheads of our scheme are also favorable. Our scheme demonstrates superior performance compared to the existing similar schemes.     

Total Synthesis of an Immunomodulatory Phosphoglycolipid from Thermophilic Bacteria

A method for the stereocontrolled synthesis of a bacterial phosphoglycolipid (PGL 1 ) isolated from thermophilic bacteria is described. The key features of the synthesis include a highly α‐selective glycosylation reaction between a trichloroacetimidate donor and a D ‐lyxose‐derived primary alcohol acceptor and the late‐stage incorporation of the phospholipid.     

Synthesis and Characterization of Novel Surfactant Molecules Based on Amphiphilic Polymers

Twelve amphiphilic polymers were synthesized using poly(ethylene glycols) (PEGs) of different molecular weights, viz. 300, 600 and1000 as hydrophilic block and aliphatic diacids namely glutaric acid, adipic acid, pimelic acid and suberic acid as hydrophobic block in presence of catalyst Conc. H₂SO₄. Synthesized polyesters were characterized by using ¹H-NMR, ¹³C-NMR and IR spectroscopy. Micellar sizes of the polymers were determined using Dynamic Light Scattering (DLS) which ranged from 127.5–354 nm. Transmission Electron Microscope (TEM) results confirm the findings of DLS. Critical Micelle Concentrations (CMC) of the synthesized polymers were determined using electrical conductivity meter which ranged from 112 to 155 mg L^?1.     

Iodine/CuI-mediated alkyne–carbonyl metathesis reaction: synthesis of 1-aryl-1,2-dihydrochromeno[2,3-b]azepine-3,6-dione

Iodine/cuprous iodide-mediated intramolecular alkyne–carbonyl metathesis reaction has been developed using 2-(N-aryl-N-propargyl)aminochromone-3-carbaldehyde as the substrate. It led to the synthesis of hitherto unreported chromeno[2,3-b]azepine-3,6-dione. The special features of this methodology are mild reaction conditions, 100% atom economy and use of inexpensive reagents. This is the first example of I₂/CuI-mediated alkyne–carbonyl metathesis reaction.     

Fock space multireference coupled cluster theory: Study of shape resonance

The complex absorbing potential along with correlated independent particle potential (CIP) Fock space multireference coupled cluster method is used for the study of resonances. We have studied shape resonance of e^?‐ F₂, e^?‐ N₂O and e^?‐CO molecules. In particular, we have studied e^?‐ F₂ scattering at different bond lengths to know whether is bound at the equilibrium bond length of F₂. © 2013 Wiley Periodicals, Inc.     

DBU-CH3I,a Potential Substitute for CH2N2 in the Preparation of Methyl Esters and Methyl Aryl Ethers: Studies with Assorted Acids

DBU-CH₃I has been poised to be a substitute for diazomethane in the preparation of methyl esters from carboxylic acids. The reactions can be carried out in commercial untreated acetone and acetonitrile, which have been exemplified with several methyl esters, otherwise it is difficult to prepare. Bis-esterification using diiodomethane can also be achieved in a similar fashion. Sufficiently acidic phenols are also conveniently O-methylated by the method.     

Metal-Stabilized [B8H8]2− Derivatives with Dodecahedral Structure in the Solid and Solution States: [(Cp2MBH3)2B8H6] (Cp=η5-C5H5; M=Zr (1-Zr) and Hf (1-Hf)).

Despite the synthesis and structural characterization of closo-hydroborate dianions, [B_nH_n]²⁻ (n=6–12) more than 50 years ago, some ambiguity remains about the structure of [B₈H₈]²⁻. Although the solid-state structure of [B₈H₈]²⁻ was established by single-crystal X-ray studies in 1969, fast rearrangements in solution at accessible temperatures prevented its detailed characterization. We therefore stabilized a derivative of [B₈H₈]²⁻ by using Cp₂MBH₃ and structurally characterized two new octaborane analogues, [(Cp₂MBH₃)₂B₈H₆] (Cp=η⁵-C₅H₅; M=Zr ( 1-Zr ) and Hf ( 1-Hf )), so that the dynamics of the B₈ skeleton were arrested. The solid-state structures of both 1-Zr and 1-Hf comprise a dodecahedron core protected by {Cp₂MBH₃} moieties on both sides of the cluster. Spectroscopic characterization (¹¹B NMR) validates the intactness of the B₈ dodecahedron core in solution as well. Theoretical calculations establish that the two exo-{Cp₂MBH₃} fragments provide structural and electronic structural stability to the B₈ core and its intact dodecahedral dianionic nature. Furthermore, we propose isodesmic equations for the formation of higher analogues of the B_n core (n>8) guarded by different group 4 transition metals. Our analysis suggests that, as we move to higher polyhedra (n>10), the formation becomes unfavourable irrespective of metal.     

Pyrazine Based Type-I Sensitizing Assemblies for Photoreduction of Cu(II) in ‘One-Pot Three-Component’ CuAAC Reaction Under Aerial Conditions

Photosensitizing assemblies of pyrazine derivative PDA have been developed which exhibit a high photostability, ‘lighted’ excited state, balanced redox potential, high transportation potential and activate oxygen via type-I pathway only. These PDA assemblies in combination with Cu(II) ions catalyze the CuAAC reaction via in situ reduction of Cu(II) ions without any reducing or stabilizing agent. The present protocol has wide substrate scope with recyclability of the catalytic system up to six catalytic cycles and is applicable to gram-scale synthesis.     

Macrocycles in dual role: ancillary ligands in metal complexes and organocatalysts for the ring-opening polymerization of lactide

Journal of Inclusion Phenomena and Macrocyclic Chemistry - In the twenty-first century, one of the central focus of polymer research in academia and industries is directed towards the design of...