Chemiluminescence of 6-aryl-2-methylimidazo[1,2-a]pyrazin-3(7H)-ones in DMSO/TMG and in diglyme/acetate buffer: support for the chemiexcitation process to generate the singlet-excited state of neutral oxyluciferin in a high quantum yield in the Cypridina (Vargula) bioluminescence mechanism

The chemiluminescence of 6-aryl-2-methylimidazo[1,2-a]pyrazin-3(7H)-ones (Cypridina luciferin analogues) in DMSO/1,1,3,3-tetramethylguanidine and in diglyme/acetate buffer was investigated. The results indicate that the reaction mechanism that produces a high chemiluminescence quantum yield involves a chemiexcitation process from a neutral dioxetanone intermediate possessing an electron-donating aryl group (σ_Ar <−0.6) to the singlet-excited state of neutral acetamidopyrazine. This result may be applied to the reaction mechanism for Cypridina (Vargula) bioluminescence.     

(1)H-NMR study of ternary platinum(II) complexes with N-(1-Naphtyl)methyl-1,2-ethanediamine or N-(9-anthrylmethyl)-1,2-ethanediamine and bipyridine or phenanthroline and restricted single bond rotation due to aromatic-aromatic ring interaction

(1)H-NMR spectra of square-planar complexes with the formula [Pt(L(1))(L(2))]X(2) where L(1) is 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) and L(2) is N-(1-naphthyl)methyl-1,2-ethanediamine (Npen) or N-(9-anthryl)methyl-1,2-ethanediamine (Aten) indicate that the N-naphthylmethyl and N-anthrylmethyl groups are forced to adopt a pseudo axial disposition due to intramolecular repulsion of hydrogen atoms of the aromatic diimines. The aromatic-aromatic interactions in the N-arylmethyl-1,2-ethanediamine complexes and aromatic diimines caused them to undergo intramolecular stacking. (1)H-NMR spectra of these complexes showed a significant concentration and temperature dependence. The monomer-dimer equilibrium was estimated, based on the concentration dependency. Restricted single bond rotation was estimated from temperature dependency data. The rotation of the anthracene ring of the [Pt(bpy)(Aten)](2+) complex showed an activation energy of ca. 38 kJ mol(-1), which is in good agreement with a mechanism involving successive rotations about single bonds with restriction by intramolecular aromatic-aromatic ring interactions.     

Rhodium-catalyzed Reformatsky-type reaction for asymmetric synthesis of difluoro-β-lactams using menthyl group as a chiral auxiliary

We developed a new methodology for the asymmetric Reformatsky-type reaction of (−)-menthyl bromodifluoroacetate (2) with imine in the presence of RhCl(PPh₃)₃. Ester 2 with the cost-effective chiral auxiliary gave (S)-difluoro-β-lactams in moderate to good yields and high diastereoselectivities through spontaneous removal of the auxiliary.     

A potential of fuzzy relations with a linear structure: The contractive case

In this paper we develop a potential theory of fuzzy relations on the positive orthant in a Euclidean space. By introducing a linear structure for fuzzy relations, the existence of a potential and its characterization by fuzzy relational equation are derived under the assumption of contraction and compactness. In the one-dimensional unimodal case, a potential is given explicity. Also, a numerical example is shown to illustrate our approaches.