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- Title
Unambiguous Proof for Alcoxycarbonyl-group Migration in Wagner-Meerwein Rearrangements.
- Authors
Berner, Daniel; Dahn, Hans; Vogel, Pierre
- Abstract
In HSO3F/SO2ClF the β-hydroxy esters Ph-CHOH-CMe2-COOR ( 1, RMe, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At −15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me2CC(Ph)COOR ( 2). By labelling 1 with 13C, singly (13C(3)) and doubly (13C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2-shift. Compound 2 is also formed in HSO3F/SO2ClF from the isomeric Me2COH-CHPh-COOR ( 3) by elimination, and less easily from the α-hydroxy ester Ph-CMe2-CHOH-COOR (5) via a phenyl 1,2-shift. Another isomer, Ph-C(OH)Me-CHMe-COOR (4) gives products different from 2. Using more acidic systems containing SbF5, the free carbenium ions 13 (Ph-CH+-CMe2-COOR) can be stabilized; they do not form 2, possibly because of complexation of the ester group with SbF5. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed.
- Publication
Helvetica Chimica Acta, 1980, Vol 63, Issue 8, p2538
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19800630849