Selective Catalytic Dehydrogenative Oxidation of Bio-Polyols to Lactic Acid.

The global demand for lactic acid (LA) is increasing due to its successful application as monomer for the manufacture of bioplastics. Although N-heterocyclic carbene (NHC) iridium complexes are promising molecular catalysts for LA synthesis, their instabilities have hindered their utilization especially in commercial applications. Here, we report that a porous self-supported NHC-iridium coordination polymer can efficiently prevent the clusterization of corresponding NHC-Ir molecules and can function as a solid molecular recyclable catalyst for dehydrogenation of bio-polyols to form LA with excellent activity (97 %) and selectivity (>99 %). A turnover number of up to 5700 could be achieved in a single batch, due to the synergistic participation of the Ba2+ and hydroxide ions, as well as the blockage of unwanted pathways by adding methanol. Our findings demonstrate a potential route for the industrial production of LA from cheap and abundant bio-polyols, including sorbitol.

Efficient Hydrogenation of Biomass Oxoacids to Lactones by Using NHC-Iridium Coordination Polymers as Solid Molecular Catalysts.

A series of NHC-iridium coordination polymers have proven to be robust, efficient and recyclable solid molecular catalysts toward the hydrogenation of biomass levulinic acid (LA) to γ-valerolactone. Along with quantitative yields attained at 0.01 mol % catalyst loading under 50 atm of H2 , the solid molecular catalyst was readily recovered and reused for 12 runs without obvious loss of the selectivity and activity. Remarkably, up to 1.2×105  TON, an unprecedented value could be achieved in this important transformation. In addition, a number of LA homologues, analogues and derivatives were well tolerated to deliver various intriguing and functional lactones in good to excellent yields, which further confirmed the feasibility of the solid molecular catalysts.

Tunable reversible metallo-hydrogels: a new platform for visual discrimination of biothiols.

By using metallo-hydrogel as a new platform, a simple and straightforward selective visual discrimination of cysteine, homocysteine and glutathione from each other as well as from other amino acids has been realized.

Suzuki-Miyaura cross-coupling of bulky anthracenyl carboxylates by using pincer nickel N-heterocyclic carbene complexes: an efficient protocol to access fluorescent anthracene derivatives.

A series of fluorescent (hetero)-aryl substituted anthracene derivatives were readily accessible from the corresponding bulky anthracen-9-yl carboxylates via Suzuki-Miyaura cross-coupling reactions by using pincer nickel N-heterocyclic carbene complex even at the catalyst loading as low as 0.1 mol% in the presence of catalytic amounts of PCy3.

Visual-size molecular recognition based on gels.

Since their discovery, stimuli-responsive organogels have garnered considerable and increasing attention from a broad range of research fields. In consideration of an one-dimensional ordered relay in anisotropic phase, the assembled gel networks can amplify various properties of the functional moieties possessed by the gelator molecules. Recently, substantial efforts have been focused on the development of facile, straightforward, and low-cost molecular recognition approaches by using nanostructured gel matrices as visual sensing platforms. In this research news, the recent progresses in macroscopic or visual-size molecular recognition for a number of homologues, isomers, and anions, as well as extremely challenging chiral enantiomers, using polymer and molecular gels are reviewed. Several strategies--including guest molecular competition, hydrogen-bonding blocking, and metal-coordination--for visual discrimination are included. Finally, the future trends and potential application in facile visual-size molecular recognition based on organogel matrices are highlighted.

Mild Negishi cross-coupling reactions catalyzed by acenaphthoimidazolylidene palladium complexes at low catalyst loadings.

Considering that the strong σ-donor property of ylidenes derived from π-extended imidazolium salts is conducive to increasing the catalytic activity of the resulting palladium N-heterocyclic carbene complexes, robust acenaphthoimidazol-ylidene palladium complexes 3a-c with varying bulky substituted groups were prepared from the corresponding acenaphthoimidazolium chlorides by heating with PdCl2 and K2CO3 in neat 3-chloropyridine in satisfactory yields. Even at a catalyst loading as low as 0.25 mol %, complex 3a exhibited extremely high catalytic activity toward Negishi cross-coupling of alkylzinc reagents with a wide range of (hetero)aryl halides under mild reaction conditions within 30 min. Besides a great number of bromoarenes, various less expensive and inactive (hetero)aryl chlorides were coupled successfully with the alkyl- and arylzinc reagents, in which active functional groups (such as -NH2) were well tolerated even in one-pot dicoupling transformations without protection. In addition, in the case of coupling with secondary alkylzinc reagents, undesired ß-hydride elimination leading to isomerized linear products was efficaciously suppressed. The catalyst system also displayed superiority in the construction of heterobiaryls through the coupling of heteroarylzinc reagents and heterocylic chloroarenes which were hardly accessible from the corresponding organoboron reagents by Suzuki-coupling reactions. Therefore, the protocol described in this paper represents a mild, general, and scalable approach to access various structurally intriguing and functionalized (hetero)aryls.

Robust acenaphthoimidazolylidene palladium complexes: highly efficient catalysts for Suzuki-Miyaura couplings with sterically hindered substrates.

Robust acenaphthoimidazolylidene palladium complexes have been demonstrated as highly efficient and general catalysts for the sterically hindered Suzuki-Miyaura cross-coupling reactions in excellent yields even with low catalyst loadings under mild reaction conditions. The high catalytic activity of these complexes highlights that, besides the "flexible steric bulky" concept, σ-donor properties of the NHC ligands are also crucial to accelerate the transformations.

Elaboration of 2-(trifluoromethyl)indoles via a cascade coupling/condensation/deacylation process.

CuI/l-proline-catalyzed coupling of 2-halotrifluoroacetanilides with beta-keto esters in anhydrous DMSO under the action of Cs2CO3 at 40-80 degrees C produces polysubstituted 2-(trifluoromethyl)indoles in good to excellent yields. This reaction is suggested to occur via a novel coupling/condensation/deacylation mechanism, and many functional groups are tolerated under these conditions.