Excited State Reactions of Oxazoles and Their Derivatives. Part I: Phototranspositions in the Ring

Heterociklički spojevi važan su dio organske kemije. Oksazol je peteročlani heterociklički spoj s dušikom i kisikom u prstenu te je dio struktura koje se izučavaju i primjenjuju u medicinskoj kemiji, kemiji farmaceutika kao i u kemiji materijala. Oksazolski prsten u pobuđenom stanju reagira pregrađivanjima prstena, za što je predloženo više reakcijskih mehanizama. U ovom dijelu pregleda detaljno je pokrivena literatura koja se odnosi na fotoizomerizacije (fototranspozicije) u prstenu izoksazola, oksazola i benzizoksazola te fototransformacije prstena uz prisutnost kisika (fotooksigenacije). Također je opisano formiranje oksazolskog prstena fotokemijskim putem. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Heterocyclic compounds are a very important part of organic chemistry. Oxazole is a five-membered heterocycle with nitrogen and oxygen atoms in the ring. Oxazole is part of complex structures used in medicinal chemistry, pharmacology, and material chemistry. In the excited state, the oxazole ring can rearrange itself via several reaction mechanisms. In this paper, an extensive literature overview is given for photoisomerisations (phototranspositions) in oxazole, isoxazole, and benzisoxazole ring. A literature review is also given for phototransformations of the ring in the presence of oxygen (photooxygenation reactions), as well as for photoformation of the oxazole ring. This work is licensed under a Creative Commons Attribution 4.0 International License

Synthesis and Photochemistry of Styryl Substituted Annelated Furan Derivatives. IV. Concentration Directed Intra- and/or Intermolecular [2+2] Cycloaddition

New cyclobutane derivatives have been synthesized by intermolecular photochemical [2+2] ethene-ethene »head-to-head« (9a,b) and »head-to-tail« (10a,b–11a,b) as well as [2+2] ethenefuran (12a,b) cycloaddition from 2-[2-(2-vinylphenyl)ethenyl]benzo[b]furan (2a) and 2-[2-(2-methylphenyl)ethenyl]benzo[b]furan (2b), respectively. All compounds were isolated and characterized by spectroscopic methods. Under the benzene solution irradiation of 5 × 10-1 mol dm-3 concentration and higher, 2-[2-(2-vinylphenyl)ethenyl]benzo[b]furan (2a) gave only dimeric products (9a–12a). At the 1 × 10-1 mol dm-3 concentration, a mixture of dimers (9a–12a) and 7,12-dihydro-7,12-methano-6H-benzo[4,5]cyclohepta[1,2-b]benzofuran (5) was formed in a ratio 2:1

Synthesis and Spectroscopic Properties of Some New cis- and trans-1-(2-Furyl)-2-(o-tolyl)ethenes

New o-methyl substituted furylphenylethenes were prepared by Wittig reaction and the cis- and trans-isomers separated by column chromatography. The isomers were characterized by their UV, iH and lSC NMR spectral data

Photoisomerization and Photocyclization of 5-Styryloxazole

This paper describes the competition of the relaxation processes (fluorescence, isomerization and cyclization) of 5-styryloxazole in the first excited singlet state. The study is carried out under mild conditions and in the first stage of irradiation to compare the photobehaviour with that reported in a previous work on preparative scale. The quantum yields of the radiative and reactive deactivation are compared with those of the analogous compounds containing pentatomic heteroaryl groups

GC-MS karakterizacija acetiliranih O-glukofuranozida: izravna glukozilacija isparljivih alkohola iz nezaštićene glukoze

O-Glucosylation of 1-pentanol, 1-octanol, 2-phenylethanol, benzyl alcohol, (±)-2-pentanol and (±)-menthol in 1,4-dioxane, using anhydrous FeCl3, afforded anomeric mixture of the corresponding glucofuranosides as major and glucopyranosides as minor products in overall yields 20–52 %. Practical advantages of GC-MS for characterizing the prepared acetylated glucofuranosides are in the focus of this paper. Glucofuranoside tetraacetate spectra contain characteristic signals of glucone (acetylated glucose) along with fragments of the aglucone moiety. The mass range was 50–600 mass units and acetyl ion was not present in the spectra, which is of interest for differentiating glucofuranoside and glucopyranoside tetraacetates.O-glukozilacija 1-pentanola, 1-oktanola, 2-feniletanola, benzil-alkohola, (±)-2-pentanola i (±)-mentola u 1,4-dioksanu, rabeći bezvodni FeCl3, dala je odgovarajuće glukofuranozide kao glavne i glukopiranozide kao sporedne produkte s ukupnim prinosima 20–52 %. Praktične prednosti GC-MS za karakterizaciju pripravljenih glukofuranozida su u žari{tu ovoga rada. Spektri glukofuranozid tetraacetata sadrže karakteristične signale glukona (acetilirane glukoze) zajedno s fragmentima aglukonskoga dijela. Interval praćenja masa bio je 50–600 masenih jedinica i acetil-ion nije bio prisutan u spektrima, {to je od interesa za razlikovanje glukofuranozid i glukopiranozid tetraacetata

Photochemistry of p-(5-Substituted-2-furyl)-o-divinylbenzenes; Substituent Effects on the Reaction Course

Irradiation of 2-[2-(2-vinylphenyl)ethenyl]furan (la) and 5-methyl- 2-[2-(2-vinylphenyl)ethenyl]furan (lb) gave 9,10-đihydro-4,9-me- thano-4ff-benzo[4,5]cyclohepta[l,2-6]furan (2a) and 9,10-dihydro- 2-methyl-4,9-methano-4H-benzo[4,5]cyclohepta[l,2-b]furan (2b), respectively, in a very good yield in addition to traces of 5. Contrary to these results, the 5-substituted furan derivatives 1 (c: R = CN; d: R = P-C6H4CH3, e: R = OCH3) gave mainly, upon irradiation under the same conditions, isomerization about the double bond, high-molecular-weight products, small amount of phenanthrenes 5 and only traces of bicyclic structure 2