Highly enantioselective carbon-carbon bond formation by Cu-catalyzed asymmetric [2,3]-sigmatropic rearrangement: application to the syntheses of seven-membered oxacycles and six-membered carbocycles

A concise route for the syntheses of enantioenriched functionalized scaffolds of medium-sized oxacycles and carbocycles employing the chiral auxiliary-mediated Cu-catalyzed ylide formation/[2,3]-sigmatropic rearrangement as a key step was developed.     

Selective iron-catalyzed transfer hydrogenation of terminal alkynes

A novel iron-catalyzed transfer hydrogenation of alkynes to the corresponding alkenes applying formic acid as a hydrogen donor is reported. An in situ combination of Fe(BF(4))(2)·6H(2)O and tetraphos allows for highly selective hydrogenation of a broad range of aromatic and aliphatic alkynes tolerating different functional groups.     

Ruthenium complex catalyzed oxidative conversion of aliphatic amines to carboxylic acids using bromamine-T: Kinetic and mechanistic study

Ruthenium(III) complex catalyzed oxidation of aliphatic amines with bromamine-T under alkaline condition proceeds efficiently to afford carboxylic acids in high conversion. Hexa-coordinated ruthenium(III) complex of the type [RuCl₂(PPh₃)(L)] (L, tridentate ligand derived by the condensation of o-phenylene diamine with salicylaldehyde) has been synthesized and it was used as a catalyst for the oxidative conversion of amines to carboxylic acids. The detailed mechanistic and kinetic investigations have been made for the oxidation reactions. Under similar experimental conditions all the amines proceed with a common oxidation mechanism and follows an identical kinetics with first-order dependence each on [Oxidant]_o and [Amine]_o, and fractional order with respect to [Catalyst] and [OH⁻]. To understand the detailed kinetics and mechanism of the reactions, the reactions have been subjected to changes in (i) dielectric permittivity, (ii) primary salt effect, (iii) halide ions and (v) temperature. The reactions were carried out at different temperature and the activation parameters have been calculated. From enthalpy–entropy relationships and Exner correlations, the isokinetic temperature (β) of 382 K, calculated is much higher than the experimental temperature (313 K), indicating that, the enthalpy factor controls the rate. The observed results have been explained by a plausible mechanism and the related rate law has been deduced. The present method developed for the oxidation of amines to carboxylic acids by bromamine-T offers several advantages including high conversion, short reaction times, and stable, cost effective and relatively non-toxic reagents which make the reaction process simple and smooth.     

Quantum chromodynamics: Working group report

This is the report of the QCD working group at WHEPP-6. Discussions and work on heavy ion collisions, polarized scattering, and collider phenomenology are reported.     

Azine-N-oxides as effective controlling groups for Rh-catalysed intermolecular alkyne hydroacylation

Heterocycle-derived aldehydes are challenging substrates in metal-catalysed hydroacylation chemistry. We show that by using azine N-oxide substituted aldehydes, good reactivity can be achieved, and that they are highly effective substrates for the intermolecular hydroacylation of alkynes. Employing a Rh(i)-catalyst, we achieve a mild and scalable aldehyde C–H activation, that permits the coupling with unactivated terminal alkynes, in good yields and with high regioselectivities (up to >20 : 1 l:b). Both substrates can tolerate a broad variety of functional groups. The reaction can also be applied to diazine aldehydes that contain a free N-lone pair. We demonstrate conversion of the hydroacylation products to the corresponding azine, through a one-pot hydroacylation/deoxygenation sequence. A one-pot hydroacylation/cyclisation, using N-Boc propargylamine, additionally leads to the synthesis of a bidentate pyrrolyl ligand.

Heterocycle-derived aldehydes are challenging substrates in metal-catalysed hydroacylation chemistry; using the N-oxide derivatives allows efficient reactions to be achieved.     

On the Existence of XOR-Based Codes for Private Information Retrieval with Private Side Information

We consider the problem of Private Information Retrieval with Private Side Information (PIR-PSI), wherein the privacy of the demand and the side information are jointly preserved. Although the capacity of the PIR-PSI setting is known, we observe that the underlying capacity-achieving code construction uses Maximum Distance Separable (MDS) codes therefore contributing to high computational complexity when retrieving the demand. Pointing at this drawback of MDS-based PIR-PSI codes, we propose XOR-based PIR-PSI codes for a simple yet non-trivial setting of two non-colluding databases and two side information files at the user. Although our codes offer substantial reduction in complexity when compared to MDS-based codes, the code-rate marginally falls short of the capacity of the PIR-PSI setting. Nevertheless, we show that our code-rate is strictly higher than that of XOR-based codes for PIR with no side information. As a result, our codes can be useful when privately downloading a file especially after having downloaded a few other messages privately from the same database at an earlier time-instant.     

Reusable Co-nanoparticles for general and selective N-alkylation of amines and ammonia with alcohols

A general cobalt-catalyzed N-alkylation of amines with alcohols by borrowing hydrogen methodology to prepare different kinds of amines is reported. The optimal catalyst for this transformation is prepared by pyrolysis of a specific templated material, which is generated in situ by mixing cobalt salts, nitrogen ligands and colloidal silica, and subsequent removal of silica. Applying this novel Co-nanoparticle-based material, >100 primary, secondary, and tertiary amines including N-methylamines and selected drug molecules were conveniently prepared starting from inexpensive and easily accessible alcohols and amines or ammonia.

A general cobalt-catalyzed N-alkylation of amines with alcohols by borrowing hydrogen methodology to prepare different kinds of amines is reported.     

Development of a General and Selective Nanostructured Cobalt Catalyst for the Hydrogenation of Benzofurans,Indoles and Benzothiophenes

The selective hydrogenation of benzofurans in the presence of a heterogeneous non-noble metal catalyst is reported. The developed optimal catalytic material consists of cobalt-cobalt oxide core–shell nanoparticles supported on silica, which has been prepared by the immobilization and pyrolysis of cobalt-DABCO-citric acid complex on silica under argon at 800 °C. This novel catalyst allows for the selective hydrogenation of simple and functionalized benzofurans to 2,3-dihydrobenzofurans as well as related heterocycles. The versatility of the reported protocol is showcased by the reduction of selected drugs and deuteration of heterocycles. Further, the stability, recycling, and reusability of the Co-nanocatalyst are demonstrated.