- Copper-catalyzed aerobic C-C bond cleavage of lactols with N-hydroxy phthalimide for synthesis of lactones
-
The transformation of cyclic hemiacetals (lactols) into lactones has been achieved by Cu-catalyzed aerobic C-C bond cleavage in the presence of N-hydroxy phthalimide (NHPI). The present process is composed of a multistep sequence including a) formation of exo-cyclic enol ethers by dehydration; b) addition of phthalimide N-oxyl radical to the enol ethers followed by trapping of the resulting C-radicals with molecular oxygen to form peroxy radicals; c) reductive generation of oxy radicals and subsequent β-radical fragmentation to generate lactones.
- Tnay, Ya Lin,Chiba, Shunsuke
-
supporting information
p. 873 - 877
(2015/04/14)
-
- Direct synthesis of 1,4-diols from alkenes by iron-catalyzed aerobic hydration and C-H hydroxylation
-
Various 1,4-diols are easily accessible from alkenes through iron-catalyzed aerobic hydration. The reaction system consists of a user-friendly iron phthalocyanine complex, sodium borohydride, and molecular oxygen. Furthermore, the effect of additional ligands on the iron complex was examined for a model reaction. The second hydroxy group is installed by direct C(sp3)-H oxygenation, which is based on a [1,5] hydrogen shift process of a transient alkoxy radical that is formed by formal hydration of the olefin. One more hydroxy group: A method for the synthesis of 1,4-diols from simple alkenes has been developed. This unusual transformation entails an iron-catalyzed aerobic hydration and is achieved with convenient reagents, such as molecular oxygen. The formation of an intermediary alkoxy radical, which undergoes a [1,5] hydrogen shift, is likely to be essential for C(sp3)-H hydroxylation. Pc=phthalocyanine.
- Hashimoto, Takuma,Hirose, Daisuke,Taniguchi, Tsuyoshi
-
supporting information
p. 2730 - 2734
(2014/03/21)
-
- Copper-catalyzed aerobic aliphatic C-H oxygenation with hydroperoxides
-
We report herein Cu-catalyzed aerobic oxygenation of aliphatic C-H bonds with hydroperoxides, which proceeds by 1,5-H radical shift of putative oxygen-centered radicals (O-radicals) derived from hydroperoxides followed by trapping of the resulting carboncentered radicals with molecular oxygen.
- Too, Pei Chui,Tnay, Ya Lin,Chiba, Shunsuke
-
supporting information
p. 1217 - 1225
(2013/07/26)
-
- An efficient oxidative lactonization of 1,4-diols catalyzed by Cp*Ru(PN) complexes
-
An efficient oxidative lactonization of 1,4-diols in acetone is accomplished by the well-defined ruthenium catalyst, whose bifunctional nature underlies the high efficiency as well as unique chemo- and regioselectivity of the reaction which provides a rapid access to γ-butyrolactones including flavor lactones hinokinin, and muricatacin.
- Ito, Masato,Osaku, Akihide,Shiibashi, Akira,Ikariya, Takao
-
p. 1821 - 1824
(2008/02/02)
-
- Oxygen activation by metal complexes and alkyl hydroperoxides. Applications of mechanistic probes to explore the role of alkoxyl radicals in alkane functionalization
-
The mechanism of the oxidation of cycloalkanes by tertiary alkyl hydroperoxides catalysed by iron(III) dichlorotris(2-pyridylmethyl)amine IIICl2(TPA)>+ and by the acetate bridged (μ-oxo) di-iron complex III(TPA)2O(OAc)>3+ has been investigated.Product studies do not support oxidation via a high valent iron-oxo intermediate (formally FeV=O), but are consistent with a mechanism involving hydrogen atom abstraction from the alkane by alkoxyl radicals derived from the hydroperoxide.In the presence of a large excess of tert-butyl hydroperoxide, the oxidation of cyclohexane yields cyclohexanone, cyclohexanol and tert-butylcyclohexyl peroxide in more than stoichiometric amounts and, in the case of the mono-iron catalyst, one equivalent of cyclohexyl choride.Replacement of Me3COOH by hydroperoxides, which could yield tert-alkoxyl radicals having much shorter lifetimes than the tert-butoxyl radical prevents oxidation of the cycloalkane.The products obtained with these hydroperoxide mechanistic probes are those derived from the fast unimolecular reactions (generally β-scissions) of the corresponding alkoxyl radicals.The inapplicability of dimethyl sulfide as a mechanistically diagnostic trap for the putative FeV=O intermediate and the value of di-tert-butyl hyponitrite as a non-iron-based source of tert-butoxyl radicals are discussed.
- MacFaul, Philip A.,Arends, Isabella W. C. E.,Ingold, Keith U.,Wayner, Danial D. M.
-
p. 135 - 146
(2007/10/03)
-
- The Role of Alkoxyl Radicals in Gif (GoAggv) Chemistry
-
The oxidation of cyclooctane using tert-alkyl hydroperoxides under GoAggv conditions has been examined using selected alkyl hydroperoxides as mechanistic probes. The results indicate that the products are formed by alkoxyl radical-induced reactions, there being no need to invoke any chemistry involving high valent iron-oxo species.
- Snelgrove, Darren W.,MacFaul, Philip A.,Ingold, Keith U.,Wayner, Danial D. M.
-
p. 823 - 826
(2007/10/03)
-
- Electron-transfer-induced reductive cleavage of phthalans: Reactivity and synthetic applications
-
The behavior of phthalan (1a) was investigated under conditions of electron transfer from alkali metals in aprotic solvents. Reaction with lithium in the presence of a catalytic amount of naphthalene in THF led to the reductive cleavage of an arylmethyl carbon-oxygen bond, with formation of a stable dilithium compound. Trapping of this intermediate with several electrophiles (alkyl halides, carbonyl derivatives, CO2) was successful. The extension of this procedure to several substituted phthalans (1b-i) was investigated, and the regiochemistry as well as the synthetic usefulness of these reactions are discussed.
- Azzena, Ugo,Demartis, Salvatore,Melloni, Giovanni
-
p. 4913 - 4919
(2007/10/03)
-