A topochemical rearrangement with multiple inversions of configuration

Citation
S. Wolfe et al., A topochemical rearrangement with multiple inversions of configuration, CAN J CHEM, 79(8), 2001, pp. 1272-1277
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
Journal title
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE
ISSN journal
0008-4042 → ACNP
Volume
79
Issue
8
Year of publication
2001
Pages
1272 - 1277
Database
ISI
SICI code
0008-4042(200108)79:8<1272:ATRWMI>2.0.ZU;2-E
Abstract
Crystalline 2-benzyloxypyridine-1-oxide rearranges slowly at room temperatu re to crystalline 1-benzyloxy-2-pyridone. No intermediates are detected whe n the process is followed by solid-state C-13 NMR. The crystal structure of the pyridine-1-oxide strongly suggests that a topochemically controlled in tramolecular process, in which the benzyl group migrates with retention of configuration, is not feasible. On the other hand, although somewhat disfav oured by initial solid-state O . . .C . . .O angles significantly less than the ideal 180 degrees, intermolecular topochemically controlled processes can be envisaged that lead, with multiple inversions of configuration, eith er to net retention of configuration or to net inversion of configuration i n the benzyl group. In contrast to the 50-80% inversion observed in solutio n, in the solid state only inversion is observed experimentally when chiral ly labelled alpha -deuteriobenzyloxypyridine-1-oxide is allowed to rearrang e.