The Tribological Effect of Mechanically Produced Micro-dents by a Micro Diamond Pyramid on Medium Carbon Steel Surfaces in Rolling-sliding Contact

In order to evaluate the effects of micro-pockets on the lubrication and the pitting durability of medium carbon steel surfaces, in the present paper, using the roller with a small number of micro-dents marked by a diamond pyramid whose total area was, to minimize the effect of work-hardening, set negligibly small compared to the contact area as the follower in a two-roller testing machine, the pitting durability was tested under poor lubrication conditions and/or severe loading levels. The results successfully demonstrate the effect of such micro-pockets on the pitting durability and scuffing resistance of surfaces in rolling-sliding contact.     

Cross-coupling reaction of chloropyrazines with ethylenes

Various chloropyrazines and their N-oxides were submitted to the cross-coupling reaction with ethylenes, such as styrene, ethyl acrylate and acrylonitrile. While the chloro-phenylpyrazines and 2-chloropyrazine 1-oxides were slugglish in this reaction system, the expected products were obtained from almost all the 2-chloro-3,6-dialkylpyrazines and their 4-oxides in moderate to good yields.     

Reduction of nitroolefin using microorganisms

Microbial reduction of 1-phenyl-2-nitro-1-propene (3) was carried out using 57 strains of yeast, 40 strains of aerobic and facultatively anaerobic bacteria and 40 strains of strictly anaerobic bacteria. Nine strains of yeast (Candida tropicalis, etc.,) had the ability to reduce (3) to 1-phenyl-2-nitropropane (1) (94.1%-60.3% yield). The ability of the aerobic and anaerobic bacteria was weaker than yeast (35.6%-14.0% and less than 5%, respectively). When 11 strains of strictly anaerobic bacteria (Clostridium innocuum etc.,) were used, a final reduced product like amphetamine (2) was detected, although the efficiency of reduction was very poor.     

Acid-promoted rearrangement of drimane type epoxy compounds and their application in natural product synthesis

The reactions of (±)-α-epoxy drimenol (4) and (±)-α-epoxy drimenyl cyanide (6) with acids (proton acid or Lewis acid) selectively gave the rearranged aldehyde (±)-13 and (±)-15 having the hydroindane skeleton, respectively, while the reactions of (±)-4 and (±)-6 with Dibal-H selectively afforded the allyl alcohol (±)-14 and (±)-16, respectively. The reactions of (8aR)-6 and (8aS)-6 with Dibal-H were applied for the determination of the absolute structure of natural 7β-acetoxy-ent-labda-8(17),13(14)E-dien-15-ol (18). The reaction of (±)-α-epoxy bicyclofarnesol (5) and (8aS)-5 with proton acid selectively provided the rearranged ketol (±)- and (8aS)-31 having the hydroindane skeleton, respectively. The optically active (8aS)-31 was converted to the natural (9S)-austrodoric acid (33).     

Photochromic metal complexes: photoregulation of both the nonlinear optical and luminescent properties

A series of dithienylethene (DTE)-containing 2,2'-bipyridine ligands and their zinc(II) diacetate, zinc(II) dichloro, rhenium(I) tricarbonyl bromo, and ruthenium(II) bis(bipyridine) complexes have been designed and synthesized, and their photochromic, photophysical, and quadratic nonlinear optical properties have been studied. Upon UV irradiation at 350 nm, the ligands and complexes undergo ring closure of the DTE units, with a good to excellent photocyclization yield. In the case of the Re(I) and Ru(II) complexes, the photocyclization of the DTE units can also be triggered using visible light, upon excitation into the metal-to-ligand charge-transfer (MLCT) bands at 400 and 490 nm, respectively. Molecular quadratic nonlinear optical (NLO) responses of the complexes have been determined by using either the electrical field induced second harmonic generation (EFISH) or harmonic light scattering (HLS) technique at 1910 nm. These studies reveal a large increase of the second-order NLO activity after UV irradiation and subsequent formation of the ring-closed isomers. This efficient enhancement clearly reflects the delocalization of the π-electron system and the formation of strong push-pull chromophores in the closed forms. The combination of the photochromic DTE-based bipyridine ligand with luminescent Re(I) and Ru(II) fragments also allows the photoregulation of the emission, leading to an efficient quenching of the ligand-based 77 K luminescence and demonstrating that the photocontrol of two optical properties, linear and nonlinear, could be achieved by using the same photochromic ligand.