Pierre Vogel, Kurt Schenk
At low temperature and in the presence of CF3COOH, SO2 undergoes Diels-Alder additions with (E)-1-acetoxybutadiene (8d) giving a 1:10 mixture of diastereomeric 6-acetoxysultines (9d + 10d). The Van't Hoff plot for equilibria 8d + SO2 reversible arrow 9d + ...
1998