No abstract

The kinetic resolution of racemic 2,3-allenoates was realized via 1,3-dipolar cycloaddition by using a bisphosphoric acid catalyst, affording the optically active 2,3-allenoates and 3-methylenepyrrolidine derivatives in high yields and enantioselectivities.

α-Aminonitriles inaccessible by traditional Strecker chemistry are obtained in redox-neutral fashion by direct amine α-cyanation/N-alkylation or alternatively, α-aminonitrile isomerization. These unprecedented transformations are catalyzed by simple carboxylic acids.

The first use of vicinal diols, ketols, or diones as 2 2π components in metal-catalyzed [2+2+2] cycloaddition is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthenacyclopentadienes that engage transient diones in successive carbonyl addition. Transfer hydrogenolysis of the resulting ruthenium(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione.

5 10 15 20 25 30 35 45 50 55 60 65In this work, a surfactant-free emulsion RAFT polymerization of methyl methacrylate (MMA) without any hydrophilic macro-RAFT agent was successfully carried out in a continuous tubular flow reactor with the mixed solvent of water and dimethyl formamide (DMF), which allowed the system to form emulsion in situ, using 4-cyano-4-(thiobenzoylthio)pentanoic acid (CTBCOOH) as the chain transfer agent and emulsion stabilizer under the synergistic effect of sodium hydroxide (NaOH), and 2,2′-azobisisobutyronitrile (AIBN) as the initiator. The resultant latexes showed good stability and the polymerization demonstrated typical "living"/controlled characteristic of RAFT polymerization: first-order kinetics, linear increase of molecular weights with monomer conversion and narrow molecular weight distributions for the resultant PMMA. NMR spectroscopy and chain-extension experiments confirmed the attachment and livingness of RAFT terminal group in the obtained polymer chain ends.

An efficient, mild and redox‐neutral iridium(III)‐catalyzed C−H annulation of N‐phenoxyacetamides for the regioselective synthesis of benzofurans has been developed by employing tertiary propargyl alcohols as the versatile coupling partners. The computed results together with the experimental data revealed that the hydroxyl group of tertiary propargyl alcohols acts as the key factor in controlling the regioselectivity and tuning the reactivity.magnified image

Cp*Rh(III)-catalyzed [4 + 3] annulation of N-methoxy amides for the direct assembly of seven-numbered 2H-azepin-2-one frameworks has been realized with gem-difluorocyclopropenes acting as innovative β-monofluorinated three sp 2 carbon sources. Either annular arylamides or linear acrylamides with the embedment of various functional groups, including DNA-tagged substrates, were found to be compatible with the established [4 + 3] reaction mode. A redox-neutral Rh(III)−Rh(V)−Rh(III) catalytic cycle, specifically via HOAc-assisted tandem site-/regioselective oxidative addition/reductive elimination/ C−F bond cleavage-enabled ring-scission involving the unprecedented olefinic C(sp 2 )−C(sp 2 ) bond cleavage, has been deduced based on experimental and computational mechanistic studies. Taken together, our findings not only identified gem-difluorocyclopropenes as potent and efficient coupling partners for C−H activation development but also provided a sound basis for the organic integration of transition-metal-catalyzed C−H functionalization with cyclopropene and fluorine chemistries.

Benzo[a]quinolizine-2-one derivatives are readily assembled from 1,2,3,4-tetrahydroisoquinoline and β-ketoaldehydes by means of a new intramolecular redox-Mannich process. These reactions are promoted by simple acetic acid and are thought to involve azomethine ylides as reactive intermediates.