Reactions with sulfinyl-stabilized carbanions

The preparation of a stabilized monofluorobenzyl carbanion by means of a remote homochiral sulfinyl group and its completely stereoselective reactions with //-p-tolylsulflnylimines have been described. The use of these reactions followed by the simultaneous removal of both chiral auxiliaries with f-BuLi, which occurs without epimerization at the benzylic position, provides the quickest entry to enantiomerically pure /3-fluorinated /3-phenylethylamines. 

Alcohol (74) undergoes an unusual extrusion of its hydroxymethyl group in the presence of sodium hydride.210 That it is a reverse reaction of nucleophilic addition to formaldehyde was confirmed by trapping experiments for the latter. Relief of steric congestion is a likely cause, with the sulfinyl also helping to stabilize the incipient carbanion. The two factors combined help to reverse the equilibrium which normally favours attack on formaldehyde. 

---