Determination of Z and E configurations in trifluoromethylated vinyl compounds: 3J(CF) coupling constants as a criterion for configurational assignments
✍ Scribed by Jean-Pierre Bégué; Danièle Bonnet-Delpon; Dany Mesureur; Michèle Ourévitch
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 272 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0749-1581
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
NOE and T~1~ proton measurements were carried out in order to determine unambiguously the Z and E configurations of some CF~3~‐trisubstituted vinylic compounds (HCRCR′CF~3~). The β‐ethylenic carbon in olefins, enol ethers and enamines is always more strongly coupled to CF~3~ in the cis compound (CF~3~ and the vinylic proton cis to each other): |^3^J(CF)|~cis~ > |^3^J(CF)|~trans~. This observation, in addition to the already known higher shielding of ^19^F NMR signal in the cis isomer, allows the safe assignments of Z and E isomers even when only one is obtained, regardless of the nature of R and R′.