69125-55-9Relevant articles and documents
Total synthesis of aeruginosin 98B
Trost, Barry M.,Kaneko, Toshiyuki,Andersen, Neil G.,Tappertzhofen, Christoph,Fahr, Bruce
supporting information, p. 18944 - 18947 (2013/01/15)
The first total synthesis of aeruginosin 98B was accomplished. The key step is a highly diastereoselective Pd-catalyzed intramolecular asymmetric allylic alkylation reaction of a diastereomeric mixture of allylic carbonates that is enabled by the use of racemic phosphine ligand L1.
Ionic-liquid-like copolymer stabilized nanocatalysts in ionic liquids: II. Rhodium-catalyzed hydrogenation of arenes
Zhao, Chen,Wang, Han-zhi,Yan, Ning,Xiao, Chao-xian,Mu, Xin-dong,Dyson, Paul J.,Kou, Yuan
, p. 33 - 40 (2008/09/18)
Rhodium nanoparticles stabilized by the ionic-liquid-like copolymer poly[(N-vinyl-2-pyrrolidone)-co-(1-vinyl-3-butylimidazolium chloride)] were used to catalyze the hydrogenation of benzene and other arenes in ILs. The nanoparticle catalysts can endure forcing conditions (75 °C, 40 bar H2), resulting in high reaction rates and high conversions compared with other nanoparticles that operate in ILs. The hydrogenation of benzene attained record total turnovers of 20,000, and the products were easily separated without being contaminated by the catalysts. Other substrates, including alkyl-substituted arenes, phenol, 4-n-propylphenol, 4-methoxylphenol, and phenyl-methanol, were studied and in most cases were found to afford partially hydrogenated products in addition to cyclohexanes. In-depth investigations on reaction optimization, including characterization of copolymers, transmission electron microscopy, and an infrared spectroscopic study of nanocatalysts, were also undertaken.
Thermal -Sigmatropic Shift of Previtamin D3 to Vitamin D3: Synthesis and Study of Pentadeuterio Derivatives
Okamura, William H.,Elnager, Hassan Y.,Ruther, Michael,Dobreff, Susanne
, p. 600 - 610 (2007/10/02)
Specifically pentadeuteriated previtamin D3 11 has been synthesized to impart thermal stability to the otherwise labile material.A 12-step synthesis of the trideuteriated A-ring 14b from p-methoxyphenol was developed and employed the addition of (methyl-d3)magnesium iodide to either the keto thiomethylene intermediate 23 or the keto dioxane 27.The enantiomerically pure trideuterio A-ring (-)-14b was then coupled with the deuteriated CD fragment 13b followed by hydrogenation to afford pentadeuteriated previtamin D3 11.A primary deuterium kinetic isotope effect (KIE) study of the -sigmatropic hydrogen migration in the conversion of previtamin D3 to vitamin D3 indicated a more "normal" primary deuterium isotope effect (as compared to a previously reported literature value of ca. 45).At 80 deg C, a kH/kD for the previtamin D3 to vitamin D3 isomerization was determined to be ca. 6.2.At 25 deg C, this -sigmatropic hydrogen migration proceeds with a kH/kD of ca. 11.4.The revisible, first-order -sigmatropic hydrogen shift of previtamin D3 to D3, determined over the temperature range 60.1-85.5 deg C is characterized by the following activation parameters: log AH = 8.8 and EaH = 19.6 kcal/mol.Deuteriated pre-D3, which rearranges over this temperature range, is characterized by the activation parameters log AD = 9.5 and EaD = 21.9 kcal/mol.