| Autor: |
Chen S; †Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States., Mercado BQ; †Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States., Bergman RG; ‡Department of Chemistry, University of California-Berkeley, Berkeley, California 94720-1416, United States.; §Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States., Ellman JA; †Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States. |
| Abstrakt: |
Diastereoselective epoxidation and regioselective ring-opening methods were developed for the synthesis of densely substituted, oxygenated piperidines from two classes of tetrahydropyridines with distinct stereochemical displays of functionalities. A new and practical in situ prepared epoxidation reagent was developed for the diastereoselective epoxidation of one class of sterically hindered tetrahydropyridines. The novel bifunctional epoxidation reagent, 2-carboperoxy-3,4,5,6-tetrafluorobenzoic acid, was designed to incorporate highly reactive percarboxy acid and pendant carboxylic acid groups, which through hydrogen bonding to the amino group successfully overrode steric effects and directed epoxidation to occur at the more hindered face of the tetrahydropyridine. Nucleophilic ring-opening of the epoxides with water, alcohols, and HF proceeded with high regioselectivity, affording piperidinol products with adjacent tetrasubstituted carbons. |
