- Ionic Pathways in the Photochemistry of Cyclic Sulfite Esters
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The photochemistry of cyclic carbonate esters proceeds by the photochemical extrusion of carbon dioxide to give 1, 3-diradicals which produce oxiranes as well as other radical derived species. The corresponding cyclic sulfite esters, upon irradiation, give intermediates that are trapped by alcohols yet generate no oxiranes. These results are consistent with ionic intermediates.
- White, Rick C.,Arney Jr, Benny E.,Perry, Jacob,Thompson, Nathan,Pithan, Phil M.,von Gradowski, Sebastian,Ihmels, Heiko
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p. 1656 - 1659
(2017/03/27)
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- Influence of functionalization of terephthalate linker on the catalytic activity of UiO-66 for epoxide ring opening
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A series of five isostructural zirconium terephthalate UiO-66 metal organic frameworks bearing different functional groups on the terephthalate linker (UiO-66-X; X = H, NH2, NO2, Br, Cl,) have been successfully prepared and characterized. UiO-66-X materials were evaluated as heterogeneous catalysts for the epoxide ring opening of styrene oxide by methanol, observing an increase in the initial reaction rate from UiO-66-H to UiO-66-Br, over one order of magnitude. The reactivity order, however, does not follow a linear relationship between the Hammett constant value of the substituent and the initial reaction rate. UiO-66-Br exhibits a wide scope, its activity depending on the structure of epoxide and nucleophile. The absence of Zr leaching to the solution together with the preservation of the UiO-66-X crystallinity confirms the stability of the framework under the reaction conditions. Nevertheless, UiO-66 undergoes a progressive deactivation upon reuse that was attributed to a strong adsorption of the reaction product.
- Blandez, Juan F.,Santiago-Portillo, Andrea,Navalón, Sergio,Giménez-Marqués, Mónica,álvaro, Mercedes,Horcajada, Patricia,García, Hermenegildo
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p. 332 - 339
(2016/12/09)
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- Allyltin tribromide: A versatile reagent involved in the ring-opening of epoxides
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This paper presents a versatile reagent for epoxide cleavage. The allyltin tribromide could act as a novel and easily prepared allylation reagent and halide atom donor to convert epoxides to the corresponding homoallyl alcohols and halohydrins in high yields with excellent regioselectivities under mild reaction conditions, respectively. It could also act as a Lewis acid to catalyze the ring opening reactions of epoxides with alcohols.
- Chen, Guohong,Wang, Xin,Jin, Xiaoqian,Liu, Lingyan,Chang, Weixing,Li, Jing
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experimental part
p. 1294 - 1301
(2010/11/05)
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- Metal-organic frameworks as efficient heterogeneous catalysts for the regioselective ring opening of epoxides
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An iron-based metal-organic framework, [Fe(BTC)] (BTC: 1,3, 5benzenetricarboxylate) is an efficient catalyst in the ring opening of styrene oxide with alcohols and aniline under mild reaction conditions. Out of the various alcohols tested for ring opening of styrene oxide, methanol was found to be the most reactive in terms of percentage conversion and reactivity. The rate of the ring-opening reaction of styrene oxide decreases as the size of the alcohol is increased, suggesting the location of active sites in micropores. [Fe(BTC)] was a truly heterogeneous catalyst and could be reused without loss of activity. The analogous compound [Cu3(BTC)2] was also found to be effective, although with somewhat lower activity than [Fe(BTC)]. The present heterogeneous protocol is compared with a homogeneous catalyst to give an insight into the reaction mechanism.
- Dhakshinamoorthy, Amarajothi,Alvaro, Mercedes,Garcia, Hermenegildo
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experimental part
p. 8530 - 8536
(2010/09/15)
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- Pyridine-directed organolithium addition to an enol ether
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A previously reported anionic rearrangement of benzyl 2-pyridyl ethers can now be accessed by a distinct and unusual mechanism: addition of alkyllithium reagents to α-(2-pyridyloxy)-styrene triggers an anionic rearrangement to afford tertiary pyridyl carbinols. The process is explained by invoking a contra-electronic, pyridine-directed carbolithiation of the enol ether π-system. Copyright
- Yang, Jingyue,Dudley, Gregory B.
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supporting information; experimental part
p. 3438 - 3442
(2011/02/24)
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- General asymmetric hydrogenation of α-branched aromatic ketones catalyzed by TolBINAP/DMAPEN-ruthenium(II) complex
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(Chemical Equation Presented) A catalyst system consisting of RuCl 2[(S)-tolbinap][(R)-dmapen] and t-C4H9OK in 2-propanol effects asymmetric hydrogenation of arylglyoxal dialkylacetals to give the α-hydroxy acetals in up to 98% ee. Hydrogenation of racemic α-amidopropiophenones under dynamic kinetic resolution predominantly gives the syn alcohols in up to 99% ee and >98% de, while the reaction of racemic bezoin methyl ether gives the anti alcohols in excellent stereoselectivity.
- Arai, Noriyoshi,Ooka, Hirohito,Azuma, Keita,Yabuuchi, Toshio,Kurono, Nobuhito,Inoue, Tsutomu,Ohkuma, Takeshi
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p. 939 - 941
(2007/10/03)
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- Novel polymer-supported ruthenium and iron complexes that catalyze the conversion of epoxides into diols or diol mono-ethers: Clean and recyclable catalysts
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Polymer-supported metal (Fe or Ru) complexes for epoxide ring opening reactions were successfully prepared by anchoring the bis(2-picolyl)amine ligand onto the polymer poly(chloromethylstyrene-co-divinylbenzene) (PCD); the catalysts showed heterogeneous catalytic activity and easy recyclability in the ring opening reactions of various epoxide substrates with methanol or H 2O at room temperature under mild and neutral conditions. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Lee, Sun Hwa,Lee, Eun Yong,Yoo, Dong-Woo,Hong, Sung Jin,Lee, Jung Hwan,Kwak, Han,Lee, Young Min,Kim, Jinheung,Kim, Cheal,Lee, Jin-Kyu
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p. 1579 - 1582
(2008/03/14)
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- Highly diastereoselective catalytic Meerwein-Ponndorf-Verley reductions
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Very practical synthesis of ephedrine analogues in high yields and enantiopurity was realized by a highly diastereoselective Meerwein-Ponndorf- Verley (MPV) reduction of protected α-amino aromatic ketones using catalytic aluminum isopropoxide. The high anti selectivity resulted from the chelation of the nitrogen anion to the aluminum. In contrast, high syn selectivity was obtained with α-alkoxy ketones and other compounds via Felkin-Ahn control.
- Yin, Jingjun,Huffman, Mark A.,Conrad, Karen M.,Armstrong III, Joseph D.
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p. 840 - 843
(2007/10/03)
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- Chemoselective conversion of aromatic epoxide and 1,2-diol to 1,3-dioxane derivatives with phenyltrimethylammonium tribromide in the presence of a catalytic amount of antimony(III) bromide
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trans-Stilbene oxide was oxidatively converted to 2-phenyl-1,3-dioxanes with phenyltrimethylammonium tribromide in the presence of various 1,3-diols and a catalytic amount of SbBr3 in DMSO at room temperature. Aromatic 1,2-diol, such as hydrobenzoin, was similarly converted to 2-aryl-1,3-dioxane derivatives under the same reaction conditions.
- Sayama, Shinsei
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p. 4001 - 4005
(2007/10/03)
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- A novel mononuclear Fe(III) mono(terpyridine) complex having labile solvent ligands and its catalytic activity
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A novel Fe mono(terpyridine) complex was successfully prepared by deliberately choosing the polymer surface-anchored terpyridine as a chelating ligand and it showed an excellent catalytic activity with an easy reusability on the ring-opening reaction of various epoxides by alcohol and water under mild and neutral conditions to give stereospecific and regioselective products.
- Yoo, Dong-Woo,Yoo, Sang-Kun,Kim, Cheal,Lee, Jin-Kyu
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p. 3931 - 3932
(2007/10/03)
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- Heterogeneously catalysed cleavage of carbon-carbon double bonds with hydrogen peroxide using calcined heteropolyacids on oxide supports
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Reaction of an alkene with aqueous hydrogen peroxide and a catalytic quantity of a heteropolyacid adsorbed onto magnesium, aluminium or zinc oxide leads to complete, rapid cleavage of the alkene to give carbonyl compounds.
- Brooks, Christopher D.,Huang, Ling-Chu,McCarron, Moya,Johnstone, Robert A. W.
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- ANION RADICAL-INDUCED DESILYLATION OF ORGANOSILANE. REACTIONS OF BENZYLSILANES WITH ALDEHYDES AND RELATED COMPOUNDS IN THE PRESENCE OF BUTYLLITHIUM OR LITHIUM METAL
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By the action of butyllithium or lithium metal in such polar aprotic solvent as DMF or HMPA in the presence of aldehydes or related compounds, some benzylsilanes suffer from anion radicalinduced desilylation forming benzyl carbanions which add to the aldehydes and related compounds.
- Kanemasa, Shuji,Tanaka, Junji,Nagahama, Hideki,Tsuge, Otohiko
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p. 1223 - 1226
(2007/10/02)
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- A NEW METHOD FOR NUCLEOPHILIC OXYMETHYLATION USING α-ALKOXYSILANES. SYNTHESIS OF UNSYMMETRICAL 1,2-DIOLS
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Desilylation of α-alkoxysilanes offers the convenient generation of carbinyl carbanions which react with a variety of carbonyl compounds giving mono-protected 1,2-diols of unsymmetrical type.Dehydration of these unsymmetrical diols leads to the regioselective formation of methyl ketones.
- Tsuge, Otohiko,Kanemasa, Shuji,Nagahama, Hideki,Tanaka, Junji
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p. 1803 - 1806
(2007/10/02)
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