Stereoselective formation of quaternary carbon centres with chiral 3-sulfonyl-1,3-oxazolidines and titanium enolates

The reaction of chiral 2-alkoxy-3-sulfonyl-1,3-oxazolidines and trichlorotitanium enolates was applied for the stereoselective construction of quaternary α-carbonyl stereocentres on cycloalkanones. The influence of different chiral 1,3-oxazolidines on the selectivity and yield of this reaction has been studied. 2-Alkoxy-3-sulfonyl-1,3-oxazolidines bearing one small group in the 4 position or two trans-arranged groups in the 4 and 5 position have been found to give the best results.