10601-39-5Relevant academic research and scientific papers
Lipase-mediated kinetic separation of a diastereomeric mixture of 4-tert-butylcyclohexanemethanol
Hiroya,Hasegawa,Watanabe,Ogasawara
, p. 379 - 381 (1995)
Diastereomerically pure trans- and cis-4-tert-butylcyclohexanemethanols have been obtained by kinetic acylation of the diastereomeric alcohol in an organic medium and by kinetic deacylation of the diastereomeric acetate in an aqueous medium both in the presence of the same lipase (lipase PS, Pseudomonas sp., Amano). The reactions take place preferentially with the trans-isomers both in organic and aqueous media to give the trans-acetate with recovery of the cis-alcohol on acylation in an organic medium,and the trans-alcohol with recovery of the cis-acetate on deacylation in an aqueous medium.
A mild, convenient, Non-Acidic conversion of enol ethers into alcohols using Hg(OAc)2 - NaBH4
Crouch, R. David,Mitten, Jeffrey V.,Span, Amelia R.,Dai, H. George
, p. 791 - 794 (1997)
Alkyl enol ethers can be converted into the corresponding alcohols in good to excellent yields by treatment with aqueous Hg(OAc)2 - NaBH4 in one reaction flask. This method is sufficiently mild to allow the survival of acid-sensitive groups such as silyl ethers, THP-protected alcohols and N-Boc-protected amines.
Alumina: Catalyst and support. XL (1) ring expansion during the dehydration of alcohols over alumina catalysts (2)
Pines, Herman,Brown, Stanley M.
, p. 74 - 87 (1971)
An investigation of ring expansion during the alumina-catalyzed dehydration of alcohols was made by the micro-pulse technique. The dehydration at 380 °C over fresh alumina of cyclobutane-, cyclopentane-, cyclohexane-, and cycloheptane-methanol yielded 99, 55, 7, and 6% of ring-expanded product, respectively, whereas over alumina which has been deactivated by passing large quantities of alcohol over it, 100, 74, 19, and 18% of the ring-expanded products were found. The stereochemical aspects of this catalytic reaction were investigated by the dehydration of cis- and trans-4-t-butylcyclohexanemethanol. More ring expansion and a higher conversion to olefins occurred in the dehydration of the cis alcohol than of the trans alcohol. In the dehydration of 1-methyl-1-cyclohexanemethanol at 310 °C, 60% of product formation involved methyl migration whereas 40% involved ring expansion. The percentage of ring expansion increased to 55 when deactivated catalyst was used. More skeletal rearrangement was found in dehydrations over alumina which had been deactivated by passing either an unsaturated or a saturated hydrocarbon over it than when fresh catalyst was used. Although the presence of sodium ions or pyridine on the catalyst lowered the amount of double bond isomerization which occurred, it did not affect the amount of skeletal rearrangement or the deactivation of the catalyst. The dehydration of 2-methylpropanol over alumina catalyst was reinvestigated and it was found that the extent of skeletal isomerization to produce n-butenes increases with the deactivation of the aluminas.
Titanocenes as Photoredox Catalysts Using Green-Light Irradiation
Flowers, Robert A.,Gans?uer, Andreas,Hilche, Tobias,Oloyede, Ugochinyere N.,Rietdijk, Niels R.,Slak, Daniel,Zhang, Zhenhua
supporting information, p. 9355 - 9359 (2020/04/30)
Irradiation of Cp2TiCl2 with green light leads to electronically excited [Cp2TiCl2]*. This complex constitutes an efficient photoredox catalyst for the reduction of epoxides and for 5-exo cyclizations of suitably unsaturated epoxides. To the best of our knowledge, our system is the first example of a molecular titanium photoredox catalyst.
Amide-Substituted Titanocenes in Hydrogen-Atom Transfer Catalysis
Zhang, Yong-Qiang,Jakoby, Verena,Stainer, Katharina,Schmer, Alexander,Klare, Sven,Bauer, Mirko,Grimme, Stefan,Cuerva, Juan Manuel,Gans?uer, Andreas
supporting information, p. 1523 - 1526 (2016/02/12)
Two new catalytic systems for hydrogen-atom transfer (HAT) catalysis involving the N-H bonds of titanocene(III) complexes with pendant amide ligands are reported. In a monometallic system, a bifunctional catalyst for radical generation and reduction through HAT catalysis depending on the coordination of the amide ligand is employed. The pendant amide ligand is used to activate Crabtree's catalyst to yield an efficient bimetallic system for radical generation and HAT catalysis.
Directed metal (oxo) aliphatic C-H hydroxylations: Overriding substrate bias
Bigi, Marinus A.,Reed, Sean A.,White, M. Christina
supporting information; experimental part, p. 9721 - 9726 (2012/07/14)
The first general strategy for a directing effect on metal (oxo)-promoted C-H hydroxylations is described. Carboxylic acid moieties on the substrate overcome unfavorable electronic, steric, and stereoelectronic biases in C-H hydroxylations catalyzed by the non-heme iron complex Fe(PDP). In a demonstration of the power of this directing effect, C-H oxidation is diverted away from an electronically favored C-1 H abstraction/rearrangement pathway in the paclitaxel framework to enable installation of C-2 oxidation in the naturally occurring oxidation state and stereoconfiguration.
Radical reduction of epoxides using a titanocene(III)/water system: Synthesis of β-deuterated alcohols and their use as internal standards in food analysis
Jimenez, Tania,Campana, Araceli G.,Bazdi, Btissam,Paradas, Miguel,Arraez-Roman, David,Segura-Carretero, Antonio,Fernandez-Gutierrez, Alberto,Oltra, J. Enrique,Robles, Rafael,Justicia, Jose,Cuerva, Juan M.
experimental part, p. 4288 - 4295 (2010/10/21)
We describe a comprehensive study into the Cp2TiCl-mediated reductive epoxide ring opening using either water as a hydrogen source or deuterium oxide as a deuterium source. The remarkable chemical profile of this reaction allows access to alcohols with anti-Markovnikov regiochemistry from different epoxides. The use of D2O as a deuterium source leads to an efficient synthesis of β-deuterated alcohols, including a deuterated sample of tyrosol, a bioactive compound contained in the leaves of the olive, which was successfully applied as an internal standard in food analysis.
Titanocene-catalyzed reductive epoxide opening: The quest for novel hydrogen atom donors
Gansaeuer, Andreas,Barchuk, Andriy,Fielenbach, Doris
, p. 2567 - 2573 (2007/10/03)
Novel hydrogen atom donors for the reductive titanocene-catalyzed epoxide opening are presented. While the potentially attractive cyclopentadienes gave only moderate yields of the desired alcohols, substituted, nontoxic, and commercially available 1,4-cyclohexadienes, e.g. γ-terpinene, in combination with more elaborate catalysts gave better or similar results than the much more expensive and carcinogenic 1,4-cyclohexadiene. In the practically important reactions of Sharpless epoxides and their derivatives excellent levels of regioselectivity for the epoxide opening could be obtained. The toxic and unpleasant to handle tert-butyl thiol could be replaced while increasing the yields of the desired products.
Axial and equatorial cyclohexylacyl and tetrahydropyranyl-2-acyl radicals. An experimental and theoretical study
DiLabio, Gino A.,Ingold, Keith U.,Roydhouse, Mark D.,Walton, John C.
, p. 4319 - 4322 (2007/10/03)
(Chemical Equation Presented) Axial and equatorial cyclohexylacyl and tetrahydropyranyl-2-acyl radicals gave distinct EPR spectra thanks to surprisingly large β-hydrogen atom hyperfine splittings that enabled them to be characterized and monitored. DFT computations indicated that the axial species (X = CH2) had a higher barrier to rotation about the (O)Cα-Cα bond. The computed difference ΔH° for the axial and equatorial radicals (R = H, X = CH2) was 0.8 kcal mol -1.
Photochemical synthesis of highly functionalized cyclopropyl ketones
Wessig, Pablo,Muehling, Olaf
, p. 865 - 893 (2007/10/03)
A series of di- and trisubstituted cyclopropyl ketones 11 were prepared by irradiation of ketones 3 and 5, which bear a leaving group adjacent to the carbonyl C-atom. The required ketones 3 could be easily synthesized either by functionalization of ketones 1 with a hypervalent iodine reagent, 2, or by O-sulfonylation of α-hydroxy ketones 7. The nitrates 5 were obtained by treatment of the corresponding α-bromo ketones with AgNO3. The irradiation of 3 and 5 must be performed in the presence of an acid scavenger (1-methyl-1H-imidazole) to obtain the cyclopropanes 11 in good yields. The synthetic efficiency of the method was, among other things, demonstrated by the preparation of a highly strained bicyclo[2.1.0]pentane 11i in good yield. The mechanism of the photochemical cyclization was investigated by means of photokinetic measurements, as well as by quantum-chemical calculations. It was shown that the presence of the leaving group substantially influences all steps of the photochemical reaction cascade. The X-ray crystal structures of 11j and exo-11k were also determined.
