NotesFAQContact Us
Collection
Advanced
Search Tips
Peer reviewed Peer reviewed
Direct linkDirect link
ERIC Number: EJ826725
Record Type: Journal
Publication Date: 2008-May
Pages: 3
Abstractor: As Provided
Reference Count: 16
ISBN: N/A
ISSN: ISSN-0021-9584
Acylation, Diastereoselective Alkylation, and Cleavage of an Oxazolidinone Chiral Auxiliary: A Multistep Asymmetric Synthesis Experiment for Advanced Undergraduates
Smith, Thomas E.; Richardson, David P.; Truran, George A.; Belecki, Katherine; Onishi, Megumi
Journal of Chemical Education, v85 n5 p695-697 May 2008
An introduction to the concepts and experimental techniques of diastereoselective synthesis using a chiral auxiliary is described. The 4-benzyl-2-oxazolidinone chiral auxiliary developed by Evans is acylated with propionic anhydride under mild conditions using DMAP as an acyl transfer catalyst. Deprotonation with NaN(TMS)[subscript 2] at -78 [degree]C leads to a rigidly chelated enolate that is alkylated by allyl iodide preferentially from the least hindered diastereoface with 98:2 selectivity. Chromatographic purification followed by hydrolytic cleavage of the auxiliary using LiOH/H[subscript 2]O[subscript 2] gives 2-methyl-4-pentenoic acid in high enantiomeric purity. This exercise gives students the opportunity to gain proficiency with the techniques of modern organic synthesis, including the manipulation of moisture-sensitive reagents, low temperature reactions, column chromatography, TLC, and NMR analysis. The experiment also provides a context for the discussion of important reaction mechanisms, such as acylation and enolate alkylation, and serves to reinforce the critical conceptual distinction between absolute and relative stereochemical control. (Contains 1 scheme and 2 notes.)
Division of Chemical Education of the American Chemical Society. Subscription Department, P.O. Box 1267, Bellmawr, NJ 08099-1267. Tel: 800-691-9846; Tel: 856-931-5825; Fax: 856-931-4115; e-mail: jchemed@egpp.com; Web site: http://www.jce.divched.org
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A