RESUMEN
The Sonogashira coupling of γ-CD-encapsulated alkynylpyrenes with terphenyl-type stopper molecules gave a doubly alkynylpyrene-threaded [4]rotaxane. The rotaxane showed only excimer emission, with a high fluorescence quantum yield of Φf =0.37, arising from the spatially restricted excimer within the cavity of the γ-CD. The excimer emission suffered little from self-quenching up to a concentration of 1.5×10(-5) M and was circularly polarized with a high glum â value of -1.5×10(-2) . The strong circularly polarized luminescence may result from the two stacked pyrenes existing in the rotaxane in an asymmetrically twisted manner.
Asunto(s)
Pirenos/química , Rotaxanos/química , Dicroismo Circular , Colorantes Fluorescentes/síntesis química , Colorantes Fluorescentes/química , Método de Montecarlo , Espectrometría de Fluorescencia , gamma-Ciclodextrinas/químicaRESUMEN
A new method for the synthesis of macrocyclic lactones, lactams, and ketones, which utilizes photoinduced intramolecular radical cyclization reactions of substrates containing tethered carboxylic acids and α,ß-unsaturated carbonyl moieties, has been uncovered. Photocyclization of the carboxylic acids tethered acrylate ester, which were prepared starting from the macrocyclic lactones, gave the two-carbon elongated macrocyclic lactones via decarboxylation. Similar photoreactions of carboxylic acid tethered acryl amide or α,ß-unsaturated ketone moieties, which were also prepared starting from the macrocyclic lactones, produced macrocyclic lactams or ketones, respectively. The simple approach can be readily applied to the preparation of a variety of macrocyclic lactones, lactams, and ketones with tunable ring sizes.
Asunto(s)
Ácidos Carboxílicos/química , Cetonas/química , Cetonas/síntesis química , Lactamas Macrocíclicas/química , Lactamas Macrocíclicas/síntesis química , Lactonas/química , Lactonas/síntesis química , Catálisis , Ciclización , Estructura Molecular , FotoquímicaRESUMEN
Deuterium exchange of a carboxy group was achieved by photochemical decarboxylation of free carboxylic acids in the presence of thiol and a small amount of D(2)O, and a deuterated product with excellent deuterium content was obtained; this reaction is a practical means of synthesizing regioselective deuterium-labelled compounds under mild reaction conditions.
Asunto(s)
Ácidos Carboxílicos/química , Deuterio/química , Catálisis , Descarboxilación , Transporte de Electrón , Espectroscopía de Resonancia Magnética , Estructura Molecular , Procesos Fotoquímicos , Estereoisomerismo , Compuestos de Sulfhidrilo/químicaRESUMEN
Single electron transfer (SET)-photochemical decarboxylation of free carboxylic acids was performed in a polar solvent using several arenes such as phenanthrene, naphthalene, 1-methylnaphthalene, biphenyl, triphenylene, and chrysene in the presence of various electron acceptors such as 1,2-, 1,3-, and 1,4-dicyanobenzenes, methyl 4-cyanobenzoate, and 1,4-dicyanonaphthalene. The decarboxylation reaction was influenced by the arenes, electron acceptors, and solvent. The best result was achieved by the photoreaction using biphenyl and 1,4-dicyanonaphthalene in aqueous acetonitrile.
Asunto(s)
Ácidos Carboxílicos/química , Solventes/química , Acetonitrilos/química , Compuestos de Bifenilo/química , Crisenos/química , Cianuros/química , Descarboxilación , Transporte de Electrón , Naftalenos/química , Fenantrenos/química , Procesos FotoquímicosRESUMEN
Inter- and intramolecular additions of alkyl radicals, generated by SET photochemical decarboxylation reactions of free carboxylic acids, to electron-deficient alkenes take place under mild conditions as part of efficient routes for the formation of N-Boc gamma-amino acids and macrocyclic lactones.
Asunto(s)
Alcanos/química , Alquenos/química , Aminoácidos/química , Ácidos Carboxílicos/química , Electrones , Lactonas/química , Procesos Fotoquímicos , Transporte de Electrón , Compuestos Macrocíclicos/químicaRESUMEN
The decarboxylation of free carboxylic acids was effected by a photogenerated cation radical of phenanthrene to yield the reduction product in the presence of a thiol, which provides an alternative method to the Barton decarboxylation procedure for aliphatic acids such as N-Boc amino acids.