New developments of thiocarbonyl compounds and sulfines in organic synthesis

The oxidation reaction of aliphatic thiocarbonyl compounds has been revisited in order to give access to the elusive corresponding sulfines and to achieve thiophilic addition of nucleophiles. Various compounds (thioketones, dithioesters, thionesters, trithiocarbonates, trithioperesters) have been treated with a peroxycarboxylic acid. In all cases the corresponding sulfines are formed, in contrast to literature expectations. Their behaviour towards nucleophiles has been investigated. The reaction with alkylithiums proved very useful: a clean and rapid thiophilic addition (no enethiolization) was observed at -78 degrees C. The resulting dithioacetal monoxides are easily transformed into carbonyl compounds (aldehydes, ketones) either by a simple mineral acid treatment or by a spontaneous rearrangement which takes place at ambient temperature. It provides a new formal entry to acyl anions (formed by an addition reaction and not by deprotonation). A second illustration of the specific properties of sulfur compounds is disclosed with a new asymmetric version of the Claisen rearrangement. Sulfur is used to facilitate the thermal course of the reaction and a sulfinyl adjacent group is introduced for diastereocontrol First examples show that this transposition indeed occurs at room temperature and with an excellent diastereomeric ratio (greater than or equal to 93.7).