Enantioselective syntheses of α-phenylalkanamines via intermediate addition of Grignard reagents to chiral hydrazones derived from (R)-(-)-2-aminobutan-1-ol

The hydrazine (R)-(-)-28 was obtained in four steps from 2-aminobutan-1-ol (R)-(-)-11, and reacted with benzaldehyde to give the hydrazone (R)-(-)-29. Nucleophilic addition of various alkyl Grignard reagents to the latter yielded the corresponding trisubstituted hydrazines (R,R)-30a-g in 70-89% yields and having d.e.s=100% (H-1 and C-13 NMR). Catalytic hydrogenolysis of these hydrazines afforded the corresponding (R)-(+)-alpha-phenylalkanamines (R)-(+)-31a-g having e.e.s=90-92% (chiral GPC). (C) 1998 Elsevier Science Ltd, All rights reserved.