136846-24-7Relevant academic research and scientific papers
Application of the Mitsunobu reaction to ephedrines and some related amino alcohols. Aspects of intramolecular participation of the amino group
Poelert, Martin A.,Hulshof, L. A.,Kellogg, Richard M.
, p. 355 - 364 (2007/10/02)
Inversion of configuration at the benzylic hydroxyl group of (1S,2S)-pseudoephedrine (2) to afford (1R,2S)-ephedrine is known to be a difficult process.The Mitsunobu reactions of 1 and 2 might offer a route to achieve such inversions.In fact Mitsunobu reactions on 1 and 2 are known to proceed via aziridines formed on intramolecular SN2 substitution by the amine functionality.The Mitsunobu reactions of N-methylated and N-benzylated ephedrines have been found to proceed via the corresponding aziridinium ions.These aziridinium ions can be opened (SN2 substitution) by nucleophiles like phthalimide and thiols.Intramolecular participation in 2 can be avoided by use of the tert-butyloxycarbonyl-(BOC) or benzyloxycarbonyl- (CBZ) protected derivatives.Mitsunobu reactions on these derivatives lead to inversion of configuration at the benzylic hydroxyl center.In contrast the BOC and CBZ derivatives of 1 are deprotected under Mitsunobu conditions.The Mitsunobu reactions of threo (1S,2S)-2-amino-1,3-propanediol have also been examined.An attempt to achieve protection by reaction with dimethylformamide dimethyl acetal led to the more substituted 2-oxazoline as established by X-ray crystallography.The desired inversion of configuration of the benzylic hydroxylic group was eventually achieved by protection of the amino substituent as the phthalimide and protection of the primary hydroxyl group as the tosylate.
Synthesis and Characterization of Chiral Oxazolidine-2-selones: A General One-Step Procedure from Readily Available Oxazolines
Peng, Jie,Barr, Mary E.,Ashburn, David A.,Odom, Jerome D.,Dunlap, R. Bruce,Silks, Louis A.
, p. 4977 - 4987 (2007/10/02)
The synthesis of a wide variety of chiral oxazolidine-2-selones from readily available 2-oxazolines has been accomplished in one step with yields ranging from 82 to 98percent.A mechanistic investigation of the formation of these selones has indicated the presence of intermediate anions which have been characterized by 13C and 77Se NMR spectroscopy.X-ray crystallographic data suggest the chiral selones exists as dimeric pairs or networks linked by unusual selenium hydrogen bonds.These chiral reagents exhibit extraordinary 77Se chemical shift sensitivity and are useful for the detection and quantitation of chirality at remotely disposed chiral centers.
