Kyosuke Satake

Facile synthesis of picene from 1,2-di(1-naphthyl)ethane by 9-fluorenone-sensitized photolysis.

A facile formation of picene was achieved by photosensitization of 1,2-di(1-naphthyl)ethane using 9-fluorenone as a sensitizer. This sensitized photoreaction is the first photochemical cyclization of ethylene-bridged naphthalene moieties to afford the picene skeleton. 5,8-Dibromopicene, prepared by this procedure using 1,2-di[1-(4-bromonaphthyl)]ethane as the substrate, was readily converted to novel functionalized picenes by conventional substitution and cross-coupling reactions.

Fluorescence response of a 4-trifluoroacetylaminophthalimide to iodide ions upon 254 nm irradiation in MeCN.

The title trifluoroacetylaminophthalimide derivative produced a violet fluorescence (lambdaFLmax 392 nm) in MeCN, and it displayed a green emission (lambdaFLmax 506 nm) after irradiation at 254 nm in the presence of iodide ions. The corresponding amidate ion of the trifluoroacetamide was identified as the green fluorescence emitter. The deprotonation reaction may be caused by proton-abstracting solvated electrons generated by a photochemical charge--transfer-to-solvent process from I(-) to MeCN.

Fluorescence response of 3-trifluoroacetylaminophthalimide to a Li+–I− ion pair induced by 254 nm photolysis in acetonitrile

A 3-trifluoroacetylaminophthalimide selectively distinguished LiI from other alkaline-metal iodides and lithium halides by a marked fluorescence colour change, from orange-yellow to sky-blue, subsequent to 254 nm photolysis.

Spectroscopic properties of meso-substituted cyanine dyes: evidences for intramolecular charge transfer from a julolidine moiety as a meso-substituent to the cyanine chromophore

Abstract Synthesis and spectral properties of cyanine dyes 1 and 2, having julolidinylethenyl and α-methyl julolidinylethenyl moieties respectively at the meso position, are described. In comparison with planer 1, the methyl group of the julolidinylethenyl group in 2 prevents the coplanarity of the whole dye system. Their characteristic electronic absorption spectra are analyzed based on the molecular orbital calculations, and the calculations well reproduce the observed data. Analysis of 1H NMR spectrum of 1 indicates that the π-electrons in the julolidinylethenyl group shift toward the cyanine main chromophore through the π-conjugation. Intramolecular charge transfer from the julolidine moiety to the cyanine main chromophore contributes to lightfastness of dyes. These findings make it possible to design a new type of stable cyanine dyes against photoirradiation with new functionalities such as intramolecular charge transfer system.

Preparation of a crown-ether-modified lophine peroxide as a guest-sensitive novel chemiluminophore and modulation of its chemiluminescence by metal cations

Abstract A guest-sensitive chemiluminophore, a novel crown-ether-modified lophine peroxide 1 , has been prepared, and its chemiluminescent behavior has been investigated in the presence of alkaline and alkaline earth metal cations. In the presence of Na+, the λmax of the chemiluminescence of peroxide 1 was blue-shifted (505 nm) compared to the case without a metal cation (566 nm). The chemiluminescent intensity was enhanced by addition of Na+ while that of Mg2+ decreased the intensity.

Plausible mechanism for the formation of 2-methoxy-2h-azepine derivatives from 3H-azepines using bromine and NBS

Formation of 2-bromo-4-t-butyl-7-methoxy-2H-azepine and 4-t-butyl-7-methoxy-2-succinimidyl-2H-azepine by the respective reactions of 5-t-butyl-2-methoxy-3H-azepine with bromine and NBS suggests a plausible mechanism for the conversion of 3H-azepine to 2H-azepine as 1,4-addition of an electrophile and a consequent 1,2-dehydrobromination. Different from the case of cycloheptatriene, reaction of 3H-azepine with bromine did not give any delocalized ionic species.

The synthesis of 3H-azepines: Thermal reorganization of 2,4- and 3,5-di-t-butyl-3a,5a-dihydro-3H-cyclobuta[b]pyrroles to 2,5- and 3,6-di-t-butyl-3H-azepines

Thermal reaction of cyclobuta [b] pyrroles, which derived by photochemical cyclization of methyl 2,5- and 3,6-di-t-butyl-1H-azepine-1-carboxylate gave di-t-butyl substituted 3H-azepines. The kinetics of the reaction were measured and the activation energy of the reorganization to 3H-azepines was estimated

Demethoxycarbonylation of methyl 2,5- and methyl 3,6-dialkyl-1H-azepine-1-carboxylates: formation and characterization of 2H-, 3H- and 4H-azepines

Demethoxycarbonylation of methyl 2,5-di-tert-butyl-1H-azepine-1-carboxylate using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) gave 3H-azepines. Under similar conditions, methyl 3,6-di-tert-butyl-1H-azepine-1-carboxylate gave not only the 3H-azepine but also the isomerized 2H- and 4H-azepines. Application of the reaction to dimethyl and diisopropyl substituted 1H-azepines showed that bulky alkyl group substitution stabilizes the seven-membered azatriene system. The thermal behaviour of the di-tert-butyl substituted azepines is discussed.

Synthesis and photochemistry of 3,6-difluoro-10,11-benzopentacyclo [6,4,0.0,0.0]dodeca-4,10-diene

9,1 2- Difluoro- and 9,12-dichlorotetracyclo[6.4.2.2.0] hexadeca-2,4,6,13,15-pentaene-1 0,1 1-dicarboxylic anhydrides (2a) and (2b) were prepared by 4πs+ 4πs photocycloaddition between cis-3,6-difluoro- or cis-3,6-dichloro-1,2-dihydrophthalic anhydride and naphthalene, respectively. 12,15-Difluoro- and 12,15-dichlorohexacyclo[8.6.0.0.0.0.0]hexadeca-3,5,7-triene-13,14-dicarboxylic anhydrides (6a) and (6b) were obtained by 2πs+ 2πs intramolecular photocycloaddition of adducts (2a) and (2b), respectively. 12,15-Difluorohexacyclo[8.6.0.0.0.0.0]hexadeca-3,5,7,13-tetraene (7a) has been synthesized by the electro-oxidative decarboxylation of anhydride (6a) and the excited singlet naphthalene has been observed on irradiation of adduct (7a), and is presumably formed via an adiabatic pathway.

Nucleophilic substitution reaction of 5-t-butyl-2-methoxy-3H-azepine with alkoxides and alkyllithium reagents: A formation of bis(5-t-butyl-3H-azepin-2-yl)-methane having a vinamidine conjugation

Reaction of 5-t-butyl-2-methoxy-3H-azepine (2) with nuclephiles (alkoxides or t-butyllithium) gave respective substitution product at 2-position of the ring. Unexpectedly, when methyllithium was used as a nucleophile, bis(5-t-butyl-3H-azepin-2-yl)methane (7), the structure of which found to be tautomeric vinamidine (7a,b), was formed. Tautomerization between 7 and 7a,b was characterized spectroscopically and theoretically based on the levels of B3LYP/6-31G(d).