1193-46-0Relevant academic research and scientific papers
Trapping a Highly Reactive Nonheme Iron Intermediate That Oxygenates Strong C-H Bonds with Stereoretention
Serrano-Plana, Joan,Oloo, Williamson N.,Acosta-Rueda, Laura,Meier, Katlyn K.,Verdejo, Bego?a,García-Espa?a, Enrique,Basallote, Manuel G.,Münck, Eckard,Que, Lawrence,Company, Anna,Costas, Miquel
, p. 15833 - 15842 (2015)
An unprecedentedly reactive iron species (2) has been generated by reaction of excess peracetic acid with a mononuclear iron complex [FeII(CF3SO3)2(PyNMe3)] (1) at cryogenic temperatures, and characterized spectroscopically. Compound 2 is kinetically competent for breaking strong C-H bonds of alkanes (BDE ≈ 100 kcal·mol-1) through a hydrogen-atom transfer mechanism, and the transformations proceed with stereoretention and regioselectively, responding to bond strength, as well as to steric and polar effects. Bimolecular reaction rates are at least an order of magnitude faster than those of the most reactive synthetic high-valent nonheme oxoiron species described to date. EPR studies in tandem with kinetic analysis show that the 490 nm chromophore of 2 is associated with two S = 1/2 species in rapid equilibrium. The minor component 2a (～5% iron) has g-values at 2.20, 2.19, and 1.99 characteristic of a low-spin iron(III) center, and it is assigned as [FeIII(OOAc)(PyNMe3)]2+, also by comparison with the EPR parameters of the structurally characterized hydroxamate analogue [FeIII(tBuCON(H)O)(PyNMe3)]2+ (4). The major component 2b (～40% iron, g-values = 2.07, 2.01, 1.95) has unusual EPR parameters, and it is proposed to be [FeV(O)(OAc)(PyNMe3)]2+, where the O-O bond in 2a has been broken. Consistent with this assignment, 2b undergoes exchange of its acetate ligand with CD3CO2D and very rapidly reacts with olefins to produce the corresponding cis-1,2-hydroxoacetate product. Therefore, this work constitutes the first example where a synthetic nonheme iron species responsible for stereospecific and site selective C-H hydroxylation is spectroscopically trapped, and its catalytic reactivity against C-H bonds can be directly interrogated by kinetic methods. The accumulated evidence indicates that 2 consists mainly of an extraordinarily reactive [FeV(O)(OAc)(PyNMe3)]2+ (2b) species capable of hydroxylating unactivated alkyl C-H bonds with stereoretention in a rapid and site-selective manner, and that exists in fast equilibrium with its [FeIII(OOAc)(PyNMe3)]2+ precursor.
(Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
supporting information, p. 1460 - 1464 (2018/04/06)
Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
supporting information, p. 2043 - 2046 (2016/02/05)
A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
Asymmetric hydrogenation of tert-alkyl ketones: DMSO effect in unification of stereoisomeric ruthenium complexes
Yamamura, Tomoya,Nakatsuka, Hiroshi,Tanaka, Shinji,Kitamura, Masato
supporting information, p. 9313 - 9315 (2013/09/12)
Face off: The ruthenium complexes of a new axially chiral PNNligand (L) are highly efficient in the presence of dimethylsulfoxide (DMSO) for hydrogenation of both functionalized and unfunctionalized tert-alkyl ketones. DMSO is thought to narrow down the many possible complex stereoisomers into a single facial L/Ru complex, thus enhancing the reactivity, selectivity, and productivity. Copyright
Dichloromethane activation. Direct methylenation of ketones and aldehydes with CH2Cl2 promoted by Mg/TiCl4/THF
Yan, Tu-Hsin,Tsai, Chia-Chung,Chien, Ching-Ting,Cho, Chia-Ching,Huang, Pei-Chen
, p. 4961 - 4963 (2007/10/03)
(Chemical Equation Presented) This Mg-TiCl4-promoted CH 2-transfer reaction of CH2Cl2 represents an extremely simple, practical, and efficient methylenation of a variety of ketones and aldehydes, especially in enolizable or sterically hindered ketones such as 2,2-dimethylcyclohexanone, camphor, and fenchone.
The Formation of Glutaric and Succinic Acids in the Oxidation of Cyclohexanol by Nitric Acid
Smith, John R. Lindsay,Richards, David I.,Thomas C. Barry,Whittaker, Mark
, p. 605 - 612 (2007/10/02)
The yields of the dibasic acid products from the oxidation of 2,2-dimethylcyclohexanol, 4-methylcyclohexanol and a mixture of cyclohexanol and cyclohexanone by nitric acid at 73 deg C have been measured.The influence of copper(II) and of vanadium(V) catalysts on the product distributions has also been investigated.The data show that in the oxidation of cyclohexanol to adipic acid the by-product glutaric acid arises predominantly by the loss of C-2 rather than C-1 and succinic acid from the loss of C-2 with C-3.The results are used to identify possible mechanisms leading to the lower dicarboxylic acids.These are investigated further by examining the oxidation products from probable intermediates and from related compounds.These studies lead to the conclusion that the intermediate 2-nitrosocyclohexanone undergoes competing reactions that lead to adipic acid or glutaric and succinic acid.
2-TOSYLOXYMETHYLCYCLANONES: RING SIZE DEPENDENCE OF FRAGMENTATION VERSUS INTRAMOLECULAR ALKYLATION
Heinz, Uwe,Adams, Elisabeth,Klintz, Ralf,Welzel, Peter
, p. 4217 - 4230 (2007/10/02)
The results reported seem to indicate, that in the presence of a nucleophilic base intramolecular alkylation is the normal reaction mode of tosyloxymethylcyclanones of type 14 and that the fragmentation reaction of five-membered compounds is the exception, probably because of the high steric energy of the alkylation transition states, e.g. of type E.
BORON FLUORIDE PROMOTED OPENING OF EPOXIDES BY ORGANOCOPPER AND CUPRATE REAGENTS
Alexakis, A.,Jachiet, D.,Normant, J. F.
, p. 5607 - 5620 (2007/10/02)
In the presence of BF3 the reaction rate of organocopper and cuprate reagents with poorly reactive epoxides is dramatically enhanced.Lithium organocuprates are the best choice among the various organocopper and cuprate reagents tested.Even the dimesityl cyanocuprate is able to react with cyclohexene oxide in excellent yield.No products of cationic rearrangements are observed.The reaction with various epoxides shows a complete stereochemical (pure anti opening) and regiochemical control (attack on the less hindered side of the epoxide).
Mechanism of the Liquid-Phase Catalytic Hydrogenolysis on Palladium/Carbon of Cyclohexene Epoxides
Accrombessi, Georges C.,Geneste, Patrick,Olive, Jean-Louis,Pavia, Andre A.
, p. 4139 - 4143 (2007/10/02)
Heterogeneous catalytic hydrogenolysis of cyclohexene epoxides on 10percent Pd/C was studied in different solvents. The principal products were found to be alcohols, formed by cleavage of one epoxide C-O bond. In addition, simultaneous cleavage of both C-O bonds gave hydrocarbons, and isomerization on the catalyst gave ketones as byproducts. The deuterolysis of cis- and trans-tert-butylcyclohexene epoxides and kinetic studies with cyclohexene epoxides carrying an axial methyl group in position 3 or 5 showed that hydrogenolysis gives preferentially axial alcohols and trans hydrogen addition, after a "roll over" on the catalyst. If one epoxide carbon carries a methyl group, conformational and steric factors come into play. C-O bond cleavage at the more substituted carbon, leading to equatorial alcohols, becomes competitive with preferential formation of axial alcohols, and steric hindrance to molecular reorientation on the catalyst causes cis as well as trans hydrogen addition.
STEREOCHEMICAL STUDIES-XXV. CONFORMATIONAL EQUILIBRIA OF 2-SUBSTITUTED 1,1-DIALKYLCYCLOHEXANES
Mursakulov, Ismail G.,Ramazanov, E. A.,Guseinov, M. M.,Zefirov, Nikolai S.,Samoshin, V. V.,Eliel, Ernest L.
, p. 1885 - 1890 (2007/10/02)
The positions of the conformational equilibria in a series of 1,1,2-trisubstituted cyclohexanes have been determined by 1H NMR.The gauche-interaction of substituents in the 1,1-dimethyl series are, in general, very close to those of monosubstituted cycloh
