Cobalt-catalyzed conjugate addition of silylacetylenes to α,β-unsaturated ketones

Catalytic addition of silylacetylenes to α,β-unsaturated ketones proceeded in the presence of a cobalt complex coordinated with a bisphosphine ligand to give high yields of β-alkynylketones.     

A new entry of nucleophiles in rhodium-catalyzed asymmetric 1,4-addition reactions: addition of organozinc reagents for the synthesis of 2-aryl-4-piperidones

A rhodium-catalyzed asymmetric 1,4-addition reaction has been applied to the synthesis of 2-aryl-4-piperidones. While other conventional nucleophiles fail, organozinc reagents have been successfully utilized for the construction of these useful compounds in very good yield and enantiomeric excess.     

A model to determine the trajectory of soil motion on a moldbroad plow surface

A mathematical model was developed to determine the soil trajectory of motion on the moldboard plow surface. With the use of the model, trajectory lines of soil particle travel were calculated based on the shape of the moldboard plow surface. Also, with the use of the values of soil properties, soil-metal coefficient of friction, the travel speed of plow and the soil modulus of elasticity, equations of forces were solved for equilibrium condition of the furrow slice passing over the moldboard surface. The use of the model can be xtended to the approximation of the soil reaction forces occurring the plowing operation. Laboratory experiments were conducted to verify the validity of the model. the moldboard shape factors used were derived from the coordinates of points describing the contours of the plow surface as measured by a profilograph.     

Ruthenium-catalyzed reaction of alkenyl triflates with zinc thiolates

A ruthenium complex coordinated with 3,4,7,8-tetramethyl-1,10-phenanthroline catalyzed the reaction of alkenyl triflates with zinc dithiolates to give alkenyl sulfides.     

Determination of peroxidase encapsulated in liposomes using homogentisic acid y-lactone chemiluminescence.

Homogentisic acid gamma-lactone (HAL) chemiluminescence (CL) was applied to the determination of horseradish peroxidase (HRP) encapsulated in liposomes. HRP was detected after the lysis of HRP-trapped liposomes with Triton X-100. CL response rate, detection limit and linear range of calibration curve for HRP in HAL CL were compared with those in piodophenol (p-IP)-enhanced luminol CL. Maximal light emission in HAL CL appeared more rapidly compared to that in p-IP enhanced luminol CL, thus resulting in remarkable reduction of CL measurement time. The detection limit for HRP in HAL CL was the same as that in p-IP-enhanced luminol CL. The linear range of calibration curve for HRP in HAL CL was improved by a factor of 50 compared with that in p-IP-enhanced luminol CL. From these results, it was found that HAL CL were superior to p-IP-enhanced luminol CL for the determination of HRP encapsulated in liposomes.     

Rhodium-catalyzed kinetic resolution of tertiary homoallyl alcohols via stereoselective carbon-carbon bond cleavage

A nonenzymatic kinetic resolution of tertiary homoallyl alcohols has been developed through a rhodium-catalyzed retro-allylation reaction under simple conditions. Selectivity factors of up to 12 have been achieved by employing (R)-H8-binap as the ligand, and the reaction can be conducted on a preparative scale.     

Simple chiral diene ligands provide high enantioselectivities in transition-metal-catalyzed conjugate addition reactions

Chiral dienes possessing the bicyclo[2.2.2]octadiene framework were prepared readily through the [4 + 2] cycloaddition of ( R)-alpha-phellandrene with methyl propiolate as the key step. Diene 9, substituted with a tertiary alcohol on one of the two double bonds, is prepared in just one step from the cycloadduct and is highly effective as a chiral ligand for rhodium-catalyzed asymmetric conjugate addition reactions, giving the corresponding addition products with higher enantioselectivity than other chiral dienes.