Synthese und Reaktionen des 5‐[p‐(Dimethylamino)phenyl]‐2,2‐dimethyl‐4‐phenyl‐3‐oxazolins

Synthesis and Reactions of 5‐[p‐(Dimethylamino)phenyl]‐2,2‐dimethyl‐4‐phenyl‐3‐oxazoline The title compound 8 has been synthesized in a one‐pot reaction of 4′‐(dimethylamino)benzoin (4) with 2‐propanone and NH3. The preparation of the intermediate 4 from 3 is the first example of an acid‐catalyzed transformation of the stable benzoin 3 into the corresponding less stable benzoin 4. Structures and yields of various by‐products occurring under different reaction conditions during the synthesis of 8 from 4 are given. The O‐atom of the 3‐oxazoline ring in 8 could be replaced by S from P2S5 yielding the 3‐thiazoline 14. Separation of the enantiomers of the racemate 8 could only be performed by transforming them into the trimethylanilinium salts 8b and 8c of (−)‐ and (+)‐10‐camphorsulfonic acid, respectively. Solid NaOAc in boiling toluene caused the precipitation of the 10‐camphorsulfonic acids from the quaternary ammonium salts as sodium salts and the removing of the third methyl group from the quaternary ammonium salts as AcOMe to give the enantiomers (−)‐(5S)‐8 and (+)‐(5R)‐8. Their absolute configurations are deduced from an X‐ray analysis of 8b.