- Synthesis of Optically Active Spirohydantoins by Asymmetric Induction. Hydantoin Formation from Amino Nitriles and Chlorosulfonyl Isocyanate
-
Conversion of 6-chloro- or 6-fluoro-2,3-dihydro-4H-1-benzopyran-4-one with optically active (S)-α-methylbenzylamine in the presence of TiCl4 to the ketimine followed by treatment in EtOH with HCN gas gives excellent yields of crystalline, enantiomerically pure (4S)-4-cyano-2,3-dihydro-6-chloro(or 6-fluoro)-4--4H-1-benzopyran.These sterically hindered amino nitriles react smoothly with chlorosulfonyl isocyanate to give, after hydrolysis, the hydantoins (4S)-2,3-dihydro-6-chloro(or 6-fluoro)-3'-spiro-2',5'-dione.The α-methylbenzyl groups can be removed by aqueous HBr/acetic acid to give the unprotected spirohydantoins.
- Sarges, Reinhard,Howard, Harry R.,Kelbaugh, Paul R.
-
p. 4081 - 4085
(2007/10/02)
-