Transformation of Amino Acids into Nonracemic 1‐(Heteroaryl)ethanamines by the Enamino Ketone Methodology

N ‐Protected L ‐phenylalanines 1a,b were transformed, via the corresponding Weinreb amides 2 and ethynyl ketones 3 , into chiral enamino ketones 4 ( Scheme 1 ). Similarly, L ‐threonine 6 was transformed in four steps into the enamino ketone 10 . Cyclocondensations of 4 and 10 with pyrazolamines 11 , benzenecarboximidamide ( 12 ), and hydrazine derivatives 18 afforded N ‐protected 1‐heteroaryl‐2‐phenylethanamines 15a – e, 16, 17 , and 21a – k and 1‐heteroaryl‐1‐aminopropan‐2‐ols 23a,b in good yields ( Schemes 2 and 3 ). Finally, deprotection by catalytic hydrogenation furnished free amines 22a – g and 24a,b ( Scheme 3 ).