195625-74-2Relevant articles and documents
Rhodium-Catalyzed Methylenation of Aldehydes
Lebel, Helene,Paquet, Valerie
, p. 320 - 328 (2004)
The rhodium-catalyzed methylenation of aldehydes using trimethylsilyldiazomethane and triphenylphosphine produces a variety of terminal alkenes in excellent yields. These mild and nonbasic reaction conditions allow the conversion of enolizable substrates (keto aldehydes and nonracemic α-substituted aldehydes) to terminal alkenes without epimerization. Optimization of the reaction conditions led to the conclusion that a variety of rhodium(I) sources can be used as catalysts. The effect of the solvent on the reaction has also been studied, and it indicates that although the THF is the best solvent, other solvents may be used. The reactivity of the system is very much dependent on the nature of the phosphine reagent. The use of an easily removable phosphine is also described. Spectroscopic studies indicate that the reaction proceeds via an unusual mechanism which leads to the in situ formation of the salt-free phosphorus ylide, methylenetriphenylphosphorane.
Stereoselective C-glycosylation reactions of pyranoses: The conformational preference and reactions of the mannosyl cation
Lucero, Claudia G.,Woerpel
, p. 2641 - 2647 (2007/10/03)
A systematic study of C-glycosylations of acetals related to mannose and other pyranoses was conducted. The C-5 alkoxyalkyl group provides only a modest influence on stereoselectivity. On the other hand, studies of pentopyranoses bearing alkoxy groups at
Synthesis of aminocyclitols by intramolecular reductive coupling of carbohydrate derived δ- and ε-functionalized oxime ethers promoted by tributyltin hydride or samarium diiodide
Marco-Contelles, Jose,Gallego, Pilar,Rodriguez-Fernandez, Mercedes,Khiar, Noureddine,Destabel, Christine,Bernabe, Manuel,Martinez-Grau, Angeles,Chiara, Jose Luis
, p. 7397 - 7412 (2007/10/03)
The intramolecular reductive coupling of a series of simple or polyoxygenated oxime ethers δ- or ε-functionalized with bromide, α,β- unsaturated ester, aldehyde, or ketone groups is reported. The cyclization of a nitrile-tethered aldehyde is also studied. These reductive couplings are promoted by tributyltin hydride or samarium diiodide. The reactions proceed under mild conditions, in good chemical yield, and with high stereoselectivity. When applied to highly functionalized substrates derived from carbohydrates, this approach provides a selective entry to enantiomerically pure aminocyclitols of varying regio- and stereochemistry. In particular, the reductive coupling reaction of carbonyl-tethered oxime ethers promoted by samarium diiodide can be performed in a one-pot sequence, following a Swern oxidation step, allowing the direct transformation of hydroxyl-tethered oxime ethers into the corresponding aminocyclitols. Moreover, the resultant O-benzylhydroxylamine products of these cyclizations can be further reduced in situ with excess samarium diiodide, in the presence of water, to the corresponding amino alcohols in excellent yields. Some transformations of these compounds are discussed.
