2963-86-2Relevant articles and documents
An original on-column oxidative cleavage of vicinal diols using alumina/potassium periodate: Application to sequential oxidation/Horner-Emmons reactions
Dakdouki, Saada C.,Villemin, Didier,Bar, Nathalie
experimental part, p. 4448 - 4454 (2011/10/01)
An unprecedented simple on-column solvent-free oxidative cleavage of vicinal diols in the solid phase using alumina/potassium metaperiodate is described herein. It permits preparation of the corresponding carbonyl compounds with high purity and good to excellent yields requiring only short reaction times. This methodology is then employed in on-column sequential oxidation/Horner-Emmons reactions for the preparation of selected stilbenes in good yields where both reaction and purification are integrated in a single unit or occur simultaneously permitting the rapid and easy preparation of small samples of pure stilbenes. The on-column oxidative cleavage of vicinal diols using alumina/potassium periodate is investigated. This approach is then applied to sequential oxidation/Horner-Emmons reactions for the simultaneous preparation and purification of stilbenes in good yields and requiring short reaction times.
Hyperaromatic stabilization of arenium ions: A remarkable cis stereoselectivity of nucleophilic trapping of β-hydroxyarenium ions by water
Lawlor, David A.,Kudavalli, Jaya Satyanarayana,MacCormac, Aoife C.,Coyne, Dara A.,Boyd, Derek R.,More O'Ferrall, Rory A.
, p. 19718 - 19728 (2012/01/31)
Cis- and trans-1,2-dihydrodiol isomers of benzene undergo acid-catalyzed dehydration to form phenol. In principle the isomeric substrates react through a common β-hydroxybenzenium (cyclohexadienyl) carbocation. Notwithstanding, the isomers show a large difference in reactivity, kcis/k trans = 4500. This difference is reduced to kcis/k trans = 440 and 50 for the 1,2-dihydrodiols of naphthalene and 9,10-dihydrodiols of phenanthrene, respectively, and to 6.9 for the dihydrodiols of the nonaromatic 7,8-double bond of acenaphthylene. Because the difference in stabilities of cis- and trans-dihydrodiols should be no more than 2-3-fold, these results imply a high cis stereoselectivity for nucleophilic trapping of a β-hydroxyarenium cation by water in the reverse of the carbocation-forming reaction. This is confirmed by studies of the 10-hydroxy-9-phenanthrenium ion generated from aqueous solvolyses of the trans-9,10-bromohydrin derivative of phenanthrene and the monotrichloroacetate ester of the phenanthrene cis-9,10-dihydrodiol. The cis stereoselectivity of forward and reverse reactions is explained by the formation (in the "forward" reaction) of different conformations of carbocation from cis- and trans-dihydrodiol reactants with respectively β-C-H and β-C-OH bonds in pseudoaxial positions with respect to the charge center of the carbocation optimal for hyperconjugation. Formation of different conformations is constrained by departure of the (protonated) OH leaving group from a pseudoaxial position. The difference in stability of the carbocations is suggested to stem (a) from the greater hyperconjugative ability of a C-H than a C-OH bond and (b) from enhanced conjugation arising from the stabilizing influence of an aromatic ring in the no-bond resonance structures representing the hyperconjugation (C 6H6OH+ ? C6H5OH H+). This is consistent with an earlier suggestion by Mulliken and a demonstration by Schleyer that the benzenium ion is subject to hyperconjugative aromatic stabilization. It is proposed that, in analogy with the terms homoconjugation and homoaromaticity, arenium ions should be considered as "hyperaromatic".
Preparation of chiral trans-5-substituted-acenaphthene-1,2-diols by baker's yeast-mediated reduction of 5-substituted-acenaphthylene-1,2-diones
Wang, Lixiao,Wang, Xingyong,Cui, Jingnan,Ren, Weimin,Meng, Nan,Wang, Jingyun,Qian, Xuhong
experimental part, p. 825 - 830 (2010/11/02)
A series of trans-5-substituted-acenaphthene-1,2-diols were obtained in 21-72% yield with 97-100% ee by baker's yeast-mediated reduction of the corresponding acenaphthylene-1,2-diones, in the presence of DMSO as a co-solvent and under vigorous agitation.
