Investigation of SmI2-mediated cyclisation of δ-iodo-α,β-unsaturated esters by deuterium 2D NMR in oriented solvents
Résumé
We have investigated the mechanism of the SmI2-mediated cyclisation of -iodo-,-unsaturated esters using protondecoupled
deuterium 1D and 2D NMR in weakly ordered polypeptide liquid crystal solvents. Analysis of the spectroscopic results
demonstrates that the cyclisation reaction takes place with concomitant and extensive racemisation at the -position and the
reason for this racemisation is discussed. We also report an efficient 2D NMR strategy for distinguishing meso- from d- and
l-diastereoisomers based on the introduction of a CD2 probe in the molecules to be studied. This approach allows determination of the diastereoisomeric and enantiomeric composition of a mixture