Rhenium(I)‐Catalyzed Generation of α,β‐Unsaturated Carbene Complex Intermediates from Propargyl Ethers for the Preparation of Cycloheptadiene Derivatives

The rhenium(I)‐catalyzed generation of α,β‐unsaturated carbene complex intermediates from easily available propargyl ethers was achieved for the concise construction of cycloheptadiene derivatives through the formal [4+3] cycloaddition reaction with siloxydienes.     

Total Synthesis of (±)‐Englerin A Using An Intermolecular [3+2] Cycloaddition Reaction of Platinum‐Containing Carbonyl Ylide

Total synthesis of (±)‐Englerin A has been achieved starting from γ,δ‐ynone 5 in 14 steps. The key feature of this synthesis is the highly efficient and stereoselective preparation of 8‐oxabicyclo[3.2.1]octane derivative 6 , a core skeleton of Englerin A, based on an inverse electron‐demand [3+2] cycloaddition reaction of the platinum‐containing carbonyl ylide, which was developed in our laboratory.     

Acid-base bifunctional catalysis of silica-alumina-supported organic amines for carbon-carbon bond-forming reactions

Acid-base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica-alumina (SA) surface with silane-coupling reagents possessing amino functional groups. The obtained SA-supported amines (SA-NR2) were characterized by solid-state 13C and 29Si NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. The solid-state NMR spectra revealed that the amines were immobilized by acid-base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA-NR2 catalysts for various carbon-carbon bond-forming reactions, such as cyano-ethoxycarbonylation, the Michael reaction, and the nitro-aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA-NR2 catalysts showed much higher catalytic activities for the carbon-carbon bond-forming reactions than heterogeneous amine catalysts using other supports, such as SiO2 and Al2O3. On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA-NR2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid-base dual-activation mechanism for the carbon-carbon bond-forming reactions is proposed.     

Collection of trace heavy metals complexed with ammonium pyrrolidinedithiocarbamate on surfactant-coated alumina sorbents

Surfactant aggregates were formed on alumina surfaces by mixing 100 mg of sodium dodecyl sulfate (SDS) and 1.5 g of gamma-alumina in 50 ml of water. The SDS-coated alumina incorporated water-insoluble metal-ammonium pyrrolidinedithiocarbamate complexes over the pH range 2-8 with a recovery of > 97%. The metals were quantitatively desorbed from the alumina with 4 mol 1(-1) nitric acid, leaving > 99% of SDS on the solid phase. They were determined by inductively coupled plasma mass spectrometry or graphite furnace atomic absorption spectrometry. The proposed method was successfully applied to the determination of traces of iron, cobalt, nickel, copper, cadmium and lead in high-purity alumina.     

Total Synthesis of (±)‐Integrifolin

The total synthesis of (±)‐integrifolin has been achieved for the first time through the stereoselective preparation of the bicyclo[5.3.0]decane skeleton based on the tungsten‐catalyzed cyclization of acyclic trienynes under photoirradiation conditions. Further key transformations of the cyclized product are the Tamao oxidation through cyclic silyl ether, the introduction of two oxygen functionalities by the oxidation of the diene and the construction of three exo‐methylene moieties.     

Controlled self-assembly of multiple diastereomeric macrocyclic boronic esters composed of two chiral units

Controlled construction of four out of five diastereomers of macrocyclic boronic ester was achieved in high yield by utilizing the self-assembly of two chiral components with the proper choice of reaction conditions. Three diastereomers could be constructed as enantiopure forms by properly changing the chirality combination between the two building blocks. Furthermore, the methodology could be applicable to the three-component self-assembly of enantiopure macrocyclic boronic esters having two different diboronic acid moieties.