J. Fuentes Mota

Partial or complete heterogeneous photocatalytic oxidation of neat toluene and 4-picoline in liquid organic oxygenated dispersions containing pure or iron-doped titania photocatalysts

Abstract The heterogeneous photocatalytic oxidation of neat toluene and 4-picoline in liquid organic oxygenated dispersions containing pure or iron-doped titania photocatalysts has been studied in a photochemical reactor radiating predominantly at 365–366 nm. The investigation correlates experimental conditions such as structural aspects, surface properties, concentration and chemical nature of the photocatalysts, and illumination times, with chemical yields and selectivity of products. For toluene, the main photocatalytic products found were benzaldehyde, benzyl alcohol and benzoic acid. In particular, our results show that traces of water present in the reaction system play an important role in the distribution of products. Likewise, the important role of the adsorption effects in photocatalysis based on semiconductors is emphasized. Thus, differences in the affinity and mode of the adsorption of different molecules (i.e., toluene, picolines) should give rise to differences in the distribution of the reaction products.

Preparation of New Glycoheptofurano[2,1-d]Imidazolidine-2-Thiones., Isomerizations to Acyclic-Sugar C-Nucleoside Analogues of Imidazole

Abstract 1-Methyl- and 1-aryl-(1,2-dideoxy-D-glyofurano)[2,1-d]-imidazolidine-2-thiones having the configurations β-D-glycero-L-gluco (4), β-D-glycero-D-ido (5—8), α-D glycerol-D-galacto (9—10) and β-D-glycero-D-talo (11, 12) are prepared by reaction of 2-amino-2-deoxy-aldoses with methyl and aryl isothiocyanates. 1-Aryl-(1,2-dideoxy–β-D-glycero-L-gluco-heptofurano)[2,1-d]imidazolidine-2-thiones (1—3) have been converted into 1-aryl-4-(D-galacto-pentitol-1-yl)-4-imidazo-line-2-thiones (24—26) by acid catalysed isomerization.

Synthesis of new C-nucleoside analogues of the imidazole from 1-aryl-(1,2-dideoxy-β-d-glycero-l-gluco-heptofurano)[2,1-d]-imidazolidine-2-thiones

Abstract Treatment of 1-phenyl(and 1- p -tolyl)-(1,2-dideoxy-β- d - glycero - l - gluco -heptofurano)[2,1- d ]imidazolidine-2-thiones ( 1 ) with trifluoroacetic acid caused isomerisation to 1-aryl-4-( d - galacto -pentitol-1-yl)-4-imidazoline-2-thiones ( 2 ) and subsequent dehydration of the sugar chain gave anomeric αβ-mixtures of 1-aryl-4-( d -lyxopyranosyl)-4-imidazoline-2-thiones ( 3 and 5 ). The S -benzylation and desulphuration of these compounds aromatised the imidazole ring to yield C -nucleoside analogues which could not be obtained by direct acid-catalysed dehydration from d - galacto -pentitol-1-yl derivatives of the imidazole.

Oxidation of 2-furoic acid via singlet oxygen generated photochemically

Abstract UV irradiation of 2-furoic acid was carried out in the presence of TiO2 and hypochlorite ions (and methanol) and in the absence of oxygen. An endoperoxide compound was photogenerated; this endoperoxide underwent subsequent transformations. The significance of the introduction of oxygen into organic substrates using chlorinated TiO2 surfaces as photocatalysts is discussed.

(Heterogeneous) Photocatalytic Oxidation of Toluene Using Pure and Iron-Doped Titania Catalysts

Summary We report here results on the photocatalytic oxidation by oxygen of neatliquid toluene, under UV-irradiation, by using unloaded and iron-loaded titania catalysts. Several experimental conditions have been selected to investigate parameters which can influence the chemical yields and the distribution of products; particular attention has been devoted to investigate the evolution of chemical yields and selectivity by extending the irradiation times up to 12 h. A discussion on the effects of structural features and the concentration of catalysts is reported. The role of water has been also investigated.

Photocatalysed Oxidation of 1,4–Pentanediol on Uv-Illuminated Suspensions of Zrtio4 Powders

Abstract The photocatalytic oxidation of 1,4–pentanediol has been investigated in UV-illuminated acetonitrile suspensions of zirconium titanate, ZrTiO 4 ., pow der under oxygenated conditions. The temporal course of the photo-oxidation of this diol was monitored by GC-MS technique. A practically total regioche mical preference for oxidation of the primary hydroxyl group in 1,4-pentane diol was observed, with 4-hydroxypentanoic acid and its γ -lactone derivati ve being generated as the sole products. Mechanistic delineation for explaining the observed regioselectivity is proposed.