A new synthetic method for α-ketosilanes employing methoxy(phenylthio)trialkylsilylmethane as an α-silylacyl anion equivalent

Development of a new synthetic method for α-ketosilanes can be achieved by a sequence of alkylation of methoxy(phenylthio)trialkylsilylmethane and oxidation with NaIO₄.     

Stereoisomers of selenilimines: isolation and reactions of 9-phenylselenoxanthene-N-arylsulfonylselenilimines

The isolates cis- and trans-9phenylselenoxanthene-N-arylsulfonylselenilimines were not interconverted thermally. cis-Isomers were converted to trans-isomers by chloramine-T or -B in a fashion of S_N2 type substitution. cis-Isomers did not rearrange but trans-isomers rearranged thermally to 9-arylsulfonamido-9-phenylselenoxanthenes, whereas both isomers underwent the base-catalyzed intermolecular rearrangement.     

Non-stereospecific ring expansions of benzothiazoline sulfoxides

Non-stereospecific ring expansions of 3-acetylbenzothiazoline sulfoxides to benzothiazines from the reaction with acetic anhydride are reported.     

Kinetics of the phosphorescent triplet states of tetracyanobenzene complexes as studied by microwave induced delayed phosphorescence

Using microwave induced delayed phosphorescence techniques we determined the populating and depopulating rate constants for the individual spin-sublevels of the phosphorescent states of tetracyanobenzene (TCNB) and its charge-transfer complexes with benzene and hexamethylbenzene (HMB) in n-hexane at 1.25 K. It was shown that the non-radiative decay process from the shortest lifetime sublevel is most responsible for the previously observed shortening in the phosphorescence lifetime of the TCNBHMB complex.     

Electron spin resonance of phosphorescent triplet molecules observation of the proton hyperfine structure of Δm = ±2 transitions in stretched poly (vinyl alcohol) films

By applying a microwave magnetic field parallel to an external magnetic field, ESR of naphthalene, quinoxaline, quinoline and isoquinoline in their phosphorescent triplet states has been studied at 77 K. The proton hyperfine structures in the Δm = ± 2 transitions were distinctly resolved, especially when the stretched film was used as a host, compared with observations in ethanol glasses. The assignment of these ESR signals was carried out with the aid of the stretched-film method.     

Palladium-catalyzed rearrangement of α-cyanoallylic acetates application to a new synthetic method for furans

Various types of α-cyanoallylic acetates were undergone the palladium-catalyzed rearrangement to give the γ-acetoxy-α,β-unsaturated nitriles in high yields. These rearranged acetates were conveniently transformed into the furan derivatives often encountered in natural products by the reduction using diisobutylaluminum hydride.     

Chemoenzymatic synthesis of naturally occurring benzyl 6-O-glycosyl-beta-D-glucopyranosides

Direct beta-glucosidation between benzyl alcohol and D-glucose (5) using the immobilized beta-glucosidase from almonds with the synthetic prepolymer ENTP-4000 gave a benzyl beta-D-glucoside (1) in 53% yield. The coupling of the benzyl beta-D-glucopyranoside congener (8) derived from 1 with phenyl 2,3,4-tri-O-acetyl-1-thio-beta-D-xylopyranoside (9), ethyl 2,3,4-tri-O-acetyl-1-thio-alpha-L-rhamnopyranoside (13), and 2,3,4-tri-O-acetyl-alpha-L-arabinopyranosyl bromide (15) afforded 10, 14, and 16, respectively, as coupled products. Deprotection of 10, 14, and 16 provided the synthetic benzyl beta-D-xylopyranosyl-(1-->6)-beta-D-glucopyranoside (2), benzyl alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranoside (3), and benzyl alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranoside (4), respectively.     

Almost-regular factorization of graphs

For integers a and b, 0 ? a ? a ? b, an [a, b]-graph G satisties a ? deg(x, G) ? b for every vertex x of G, and an [a, b]-factor is a spanning subgraph F such that a ? deg(x, F) ? b for every vertex x of F. An [a, b]-factor is almost-regular if b = a + 1. A graph is [a, b]-factorable if its edges can be decomposed into [a, b]-factors. When both K and t are positive integers and s is a nonnegative integer, we prove that every [(12K + 2)t + 2ks, (12k + 4)t + 2ks]-graph is [2k,2k + 1]-factorable. As its corollary, we prove that every [r.r + 1]-graph with r ? 12k² + 2k is [2k + 1]-factorable, which is a partial extension of the two results, one by Thomassen and the other by Era.