10601-39-5Relevant articles and documents
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Bergbreiter,D.E.,Whitesides,G.M.
, p. 4937 - 4944 (1974)
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Bundel et al.
, (1972)
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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.
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.
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.
