14575-92-9Relevant articles and documents
A novel and efficient catalytic epoxidation of olefins and monoterpenes with microencapsulated Lewis base adducts of methyltrioxorhenium
Saladino, Raffaele,Andreoni, Alessia,Neri, Veronica,Crestini, Claudia
, p. 1069 - 1075 (2005)
The reactivity of methyltrioxorhenium in the epoxidation of olefins can be tuned by the presence of Lewis bases as ligands of the metal center. Unfortunately, a large excess of ligand is usually required to obtain high yields and selectivities mainly because of the fluxional behaviour that these compounds show in solution. We describe here the microencapsulation technique that can resolve this problem. Microencapsulated Lewis base adducts of methyltrioxorhenium with nitrogen containing ligands are highly efficient and selective catalysts for the epoxidation of several olefins and monoterpenes with hydrogen peroxide even in the case of the most sensitive substrates. These systems show the advantages of the ligand accelerated catalysis and the benefits of heterogeneous compounds. They can be easily recovered from the reaction mixture and used for more transformations.
Photocatalytic oxygenation of hydrocarbons with (tetraarylporphyrinato)iron(III) complexes and molecular oxygen. Comparison with microsomal cytochrome P-450 mediated oxygenation reactions
Weber,Hommel,Behling,Haufe,Hennig
, p. 2400 - 2408 (1994)
Photocatalytic oxygenation of various alkenes with dioxygen and (5,10,15,20-tetraarylporphyrinato)iron(III) complexes yielded allylic oxygenation products and/or epoxides. The product composition was found to be influenced both by the nature of the used substrate and by the concentrations, as well as the axial ligands. Alkenes with strained carbon double bonds gave preferentially epoxides whereas mainly allylic oxygenation was observed for unstrained alkenes. The proposed reaction mechanisms involve the oxoiron(IV) porphyrinate (P)FeIV=O as the catalytically active species whose selectivity is related to that of the oxygenation of α-pinene with microsomal cytochromes P-450 and P-420 obtained from the yeast strain Torulopsis apicola. Oxygenation products observed with both systems give evidence for the occurrence of an oxoiron(IV) heme species in microsomal cytochrome P-450 mediated reactions. The enantio-, regio-, and chemoselectivities of the photooxygenation with iron(III) porphyrins and molecular oxygen are explained in terms of abstraction of an allylic hydrogen atom, catalyzed autoxidation and "direct" oxygen-transfer reactions.
Enantiospecific synthesis, separation and olfactory evaluation of all diastereomers of a homologue of the sandalwood odorant Polysantol
Castro, Juan M.,Linares-Palomino, Pablo J.,Salido, Sofía,Altarejos, Joaquín,Nogueras, Manuel,Sánchez, Adolfo
, p. 11192 - 11203 (2005)
The four stereoisomers of (5E)-4,4-dimethyl-6-(2′,2′,3′- trimethylcyclopent-3′-en-1′-yl)-hex-5-en-3-ol, a homologue of the valuable sandalwood-type odorant Polysantol, were enantiospecifically synthesized from (+)- and (-)-α-pinene, through (-)- and (+)-campholenic aldehyde, by aldol condensation with 3-pentanone, deconjugative α-methylation and reduction. The mixtures of epimeric alcohols obtained after reduction were separated by means of derivatization with (-)-(1S)-camphanic chloride. The enantiomerically pure final products were evaluated organoleptically.
Aerobic epoxidation of natural terpenes: Study of the catalytic activity of new Ru-1,2,4-triazepine compelxes
Fdil, Na?ma,Ait Itto, My Youssef,Ait Ali, Mustapha,Karim, Abdellah,Daran, Jean-Claude
, p. 8769 - 8771 (2002)
Aerobic epoxidation of a range of natural terpenic olefines was carried out by using the triazepinic complexes [RuCl(TAZO)(p-cymene)] C1 and [Ru(TAZS)(p-cymene)]2 C2, recently prepared from [RuCl2(p-cymene)]2 and the corresponding 1,2,4-triazepines (HTAZO and H2TAZS). While, good similar stereoselectivity was observed for the two complexes, C1 was shown to be more effective and chemioselective.
Manganese(III) porphyrin catalysts for the oxidation of terpene derivatives: A comparative study
Maraval, Valerie,Ancel, Jean-Erick,Meunier, Bernard
, p. 349 - 357 (2002)
A comparative study involving four manganese(III) porphyrin catalysts combined with two different oxidants (sodium hypochlorite and potassium monopersulfate) has been performed in the epoxidation of three terpene derivatives. The catalytic oxidation of α-pinene produces selectively 100% of the epoxide or 65% of allylic oxidation products, only by modification of the substituents on the meso-positions of the metalloporphyrin catalyst. The catalytic oxidation of the 5-vinyl-2-norbornene is regio- and stereoselective, producing only the exo-2,3-epoxy-5-vinylnorbornane. With α-terpinene, a conjugated di-olefin, an oxidative dehydrogenation reaction was surprisingly observed, producing p-cymene as a major compound.
Opening of epoxide rings catalyzed by niobium pentachloride
Constantino, Mauricio Gomes,Lacerda Jr., Valdemar,Invernize, Paulo Roberto,Filho, Luiz Carlos Da Silva,Da Silva, Gil Valdo Jose
, p. 3529 - 3539 (2008/03/13)
The behavior of several epoxides when treated with NbCl5 was studied. In general, the studied epoxides reacted rapidly with NbCl5, giving, in most cases, more than one product (chlorohydrins, products containing solvent residues, as well as rearrangement products). A detailed study was performed to verify the effects of the temperature (rt, 0°C, or -78°C) and of the NbCl5 molar concentration on the composition of the products, yield, and time required for the reactions. Copyright Taylor & Francis Group, LLC.
Reactions of epoxides prepared from some monoterpenes with acetic anhydride on aluminosilicate catalysts
Tatarova,Korchagina,Volcho,Salakhutdinov,Barkhash
, p. 1076 - 1082 (2007/10/03)
Reactions of epoxides prepared from α-, β-pinenes and camphene with acetic anhydride on aluminosilicate catalysts (clay K-10, zeolite β) were investigated affording various products of skeleton rearrangements: mono- and diacetates with five- and six-membered rings, and also with norbornane and pinane cores.
Substrate-induced diastereoselectivity in the dimethyldioxirane epoxidation of simple alkenes and dienes
Asouti,Hadjiarapoglou
, p. 1847 - 1850 (2007/10/03)
Various alkenes and dienes, such as (R)- or (S)-limonene 2, 2-carene 6, 3-carene 8, (R)-α-pinene 10, (S)-α-pinene 12, and endo-dicyclopentadiene 14 were transformed into the corresponding mono- and bis-epoxides by epoxidation with dimethyldioxirane (as an acetone solution). The selectivity observed in these epoxidations is explained by the assumption of hydrogen bonding between bridge protons and the dioxirane.
Diastereoselective epoxidation of olefins by organo sulfonic peracids, II
Kluge,Schulz,Liebsch
, p. 2957 - 2976 (2007/10/03)
We have investigated the behaviour of sulfonic peracids 2 in situ generated towards olefins 7a, 7b, 9, 11, 14, 16, 18, allylic acid and homoallylic alcohols 20, 22, 24, 26, 28, 30, 33 and α,β-unsaturated ketones 35, 37, 39. Generally, the epoxidation proceeds in a peracid-like manner with greater diastereoselectivity than those by common oxidants. In particular, the epoxidation of Δ4 3-ketosteroids 39a-i led to 4α,5α-epoxides 40a-i with remarkable high de-values. Enhanced α-selectivity was also found in the epoxidation of cholesterol 28b. Due to the mild reaction conditions, even acid sensitive epoxides 8a, 8b, 10, 12, 13, 15, 17, 19 were obtained in good yields.
Sulfonic peracids - III. Heteroatom oxidation and chemoselectivity
Kluge,Schulz,Liebsch
, p. 5773 - 5782 (2007/10/03)
We have investigated the p-toluenesulfonic peracid (2) generated in situ in the oxidation of different types of compounds containing nitrogen and/or sulfur. The sulfonic peracid 2 shows a remarkable chemoselectivity characterized by a preferred oxidation of sulfides to the sulfones in the presence of amines or olefins and a strong dependence on the nature of the amine in the competitive oxidation of olefins and amines.
