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Biomimetic Oxidation (biomimetic + oxidation)
Selected AbstractsRapid and Highly Chemoselective Biomimetic Oxidation of Organosulfur Compounds with Tetrabutylammonium Peroxymonosulfate in the Presence of Manganese meso-Tetraphenylporphyrin and Imidazole.CHEMINFORM, Issue 33 2004Nasser Iranpoor Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Simple and Highly Selective Biomimetic Oxidation of Alcohols and Epoxides with N-Bromosuccinimide in the Presence of ,-Cyclodextrin in Water.CHEMINFORM, Issue 30 2004N. Srilakshmi Krishnaveni No abstract is available for this article. [source] Highly Efficient Biomimetic Oxidation of Sulfide to Sulfone by Hydrogen Peroxide in the Presence of Manganese meso -TetraphenylporphyrinCHINESE JOURNAL OF CHEMISTRY, Issue 6 2008Xian-Tai ZHOU Abstract Low amount of manganese meso -tetraphenyl porphyrin [Mn(TPP)] was used for highly efficient selective oxidation of sulfide to sulfone by hydrogen peroxide at room temperature. Sulfones were produced directly with yields generally around 90% while the catalyst concentration was only 4×10,5 mol·L,1. In a large-scale experiment of thioanisole oxidation, the isolated yield of sulfone (87%) was obtained and the turnover number (TON) reached up to 8×106, which is the highest TON for the oxidation systems of sulfide to sulfone catalyzed by metalloporphyrins. [source] Novel Model Sulfur Compounds as Mechanistic Probes for Enzymatic and Biomimetic OxidationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2005Alicia B. Peñéñory Abstract To test for the intermediacy of sulfide radical cations in biomimetic and enzymatic oxidations, the sulfides PhSCH3 (1a), PhSCH2Ph (1b), PhSCHPh2 (1c), PhSCPh3 (1d), CH3SCHPh2 (2), PhSCH2CH=CH2 (3), PhSCH2CH=CHPh (4) and CH3SCH2CH=CHPh (5) were studied, and their results were compared to those obtained for the corresponding chemical electron transfer (CET) and photoinduced electron transfer (PET) oxidations. The radical cations generated from 3,5 by CET in the presence of cerium(IV) ammonium nitrate (CAN) yielded only fragmentation products from the alkyl cations and the thiyl radicals (RS·), whereas 2·+ afforded both fragmentation and mainly ,-deprotonation products. Photochemical treatment of the sulfides 1a and 1b with C(NO2)4 gave only the corresponding sulfoxides, while fragmentation was the main pathway for the photoreactions of 1c, 2 and 5, and for 1d only this latter process was observed. These results support our selection of the sulfides RSCHPh2, RSCH2CH=CHPh (R = Me, Ph) and PhSCPh3 as models for the biomimetic and enzymatic studies. As evidenced by the sulfoxides and sulfones detected as unique products both in protic and in aprotic solvents, it is proposed that the mechanism of the biomimetic sulfoxidations of sulfides 1c and 2,5 by TPPFeIIICl is direct oxygen transfer. Three enzymes , Coprinus cinereus peroxidase (CiP), horseradish peroxidase (HRP) and chloroperoxidase (CPO) , were studied in the oxidation of sulfides 1a, 2, 4 and 5. The use of a racemic alkyl hydroperoxide in the CiP enzymatic oxidation of sulfides 5 and 2 yielded the corresponding sulfoxides (23 and 29%) and the aldehyde or benzophenone (5%), respectively. These results suggest the involvement of an ET process for the CiP-catalysed oxidation. Fragmentation products were observed in the enzymatic oxidation of sulfide 4 with HRP, which confirms the previously proposed ET mechanism. On the other hand, the CPO-enzymatic oxidation of sulfide 5 yielded only the corresponding sulfoxide, as would be expected for a direct oxygen-transfer or oxene mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Asymmetric biomimetic oxidations of phenols using oxazolidines as chiral auxiliaries: the enantioselective synthesis of (+)- and (,)-dehydrodiconiferyl alcohol,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8-9 2006Maurizio Bruschi Abstract Stereoselective bimolecular radical coupling reactions of phenylpropenoid phenols are described. Evans's 2-oxazolidinone 11a,d derivatives of ferulic acid were prepared and oxidized to give dimeric benzofuran neolignan structures 12,13a,d in 40,50% overall yields. The chiral phenols were dimerized either enzymatically with hydrogen peroxide and horseradish peroxidase (HRP) or with silver oxide. The enantioselectivity after reductive cleavage of the chiral auxiliaries to give dehydrodiconiferyl alcohol ranged from 18% to 62% enantiomeric excess. The conformational analysis and the activation energy using semiempirical PM3 calculations on the intermediate quinomethides is used to explain the observed stereoselectivity. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||