Brønsted Acid-Catalyzed, Asymmetric Allenoate Claisen Reaction.

An auxiliary-based protocol is described for an asymmetric allenoate Claisen rearrangement. Silicated tosic acid (10 mol %) was used as an inexpensive, user-friendly catalyst. Stereochemical analysis revealed a preferential attack at the face of prostereogenic olefin.

Climate policies that achieved major emission reductions: Global evidence from two decades.

Meeting the Paris Agreement's climate targets necessitates better knowledge about which climate policies work in reducing emissions at the necessary scale. We provide a global, systematic ex post evaluation to identify policy combinations that have led to large emission reductions out of 1500 climate policies implemented between 1998 and 2022 across 41 countries from six continents. Our approach integrates a comprehensive climate policy database with a machine learning-based extension of the common difference-in-differences approach.

Silver-Catalyzed, -Formylation of Amines Using Glycol Ethers.

A silver-catalyzed protocol was found to afford the -formylation of amines in moderate-to-good yields. Ethylene glycol-derived, oligomeric ethers were found to function as the formylating agent, with 1,4-dioxane affording the best results. This reaction does not require the use of stoichiometric activating reagents, and avoids the use of explosive reagents or toxic gases, such as CO, as the C1 synthon.

Auricular stimulation vs. expressive writing for exam anxiety in medical students - A randomized crossover investigation.

Objective: Auricular stimulation (AS) is a promising method in the treatment of situational anxiety. Expressive writing (EW) is an established psychological method, which reduces test anxiety and improves exam results. The aim of this crossover trial was to compare AS with EW, and with the no intervention (NI) condition, for treatment of exam anxiety.

"Click" and Olefin Metathesis Chemistry in Water at Room Temperature Enabled by Biodegradable Micelles.

The two laboratory reactions focus on teaching several concepts associated with green chemistry. Each uses a commercial, nontoxic, and biodegradable surfactant, TPGS-750-M, to promote organic reactions within the lipophilic cores of nanoscale micelles in water. These experiments are based on work by K.

Characterization and dynamics of substituted ruthenacyclobutanes relevant to the olefin cross-metathesis reaction.

The reaction of the phosphonium alkylidene [(H(2)IMes)RuCl(2)=CHP(Cy)(3))](+) BF(4)(-) with propene, 1-butene, and 1-hexene at -45 °C affords various substituted, metathesis-active ruthenacycles. These metallacycles were found to equilibrate over extended reaction times in response to decreases in ethylene concentrations, which favored increased populations of α-monosubstituted and α,α'-disubstituted (both cis and trans) ruthenacycles. On an NMR time scale, rapid chemical exchange was found to preferentially occur between the β-hydrogens of the cis and trans stereoisomers prior to olefin exchange.

Decomposition of ruthenium olefin metathesis catalysts.

The decomposition of a series of ruthenium metathesis catalysts has been examined using methylidene species as model complexes. All of the phosphine-containing methylidene complexes decomposed to generate methylphosphonium salts, and their decomposition routes followed first-order kinetics. The formation of these salts in high conversion, coupled with the observed kinetic behavior for this reaction, suggests that the major decomposition pathway involves nucleophilic attack of a dissociated phosphine on the methylidene carbon.

Ruthenium metallacycles derived from 14-electron complexes. New insights into olefin metathesis intermediates.

Ruthenium(IV) metallacycles derived from both ethylene and propene are reported. The propene-derived metallacycles represent the first observed examples of substituted ruthenacyclobutanes and offer new insight into the preferred stereochemical orientation about metathesis intermediates. In addition, a metallacycle possessing an unsymmetrical N-heterocyclic carbene (NHC) ligand was prepared and investigated to ascertain the dynamics of the NHC relative to the metallacycle ring.

Asymmetric catalytic Mannich reactions catalyzed by urea derivatives: enantioselective synthesis of beta-aryl-beta-amino acids.

Highly enantioselective addition reactions between silyl ketene acetals and N-Boc aldimines are catalyzed by the thiourea-based catalyst 1c. Extraordinary scope is observed in this methodology with regard to the imine substrate, with aryl and heteroaromatic derivatives generally affording nearly quantitative yields of beta-amino ester product in up to 98% enantioselectivity.