LiClO4-Induced Mannich Reaction − Diastereo- and Enantioselective Synthesis of β-Amino Ketones by Addition of Enamines, Imines or Silylenolethers to Aldehydes and Dialkyltrimethylsilylamines

LiClO4-mediated one-pot reactions of aldehydes with (trimethylsilyl)dialkylamines 2, 5 or 19 and C nucleophiles such as enamines 3, 10 and 12, imines 7 and 11 or (trimethylsilyl)enol ethers 8 and 9 afforded the corresponding aminoalkylation products in high yields. Whereas by using aromatic aldehydes, such as benzaldehyde, pyridine-3-carbaldehyde or thiophene-2-carbaldehyde, high diasteroselectivity was achieved, the aminoalkylation of aliphatic aldehydes such as isobutyraldehyde and pivalaldehyde lacked diastereoselectivity. Enantioselective Mannich reactions using chiral enamines 22 and 23 are reported.