Asymmetric Synthesis of α-Substituted β-Amino Sulfones by Aza-Michael Addition to Alkenyl Sulfones and Subsequent α-Alkylation

✍ Scribed by Dieter Enders; Stephan Frank Müller; Gerhard Raabe; Jan Runsink

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 485 KB
• Volume: 2000
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/(sici)1099-0690(200003)2000:6<879::aid-ejoc879>3.0.co;2-e

✦ Synopsis

The aza-Michael addition of enantiopure 1-aminopyrrolidines to (E)-alkenyl sulfones in the presence of a catalytic amount of ytterbium trifluoromethanesulfonate [Yb(OTf) 3 ] yields β-hydrazino sulfones in moderate to good yields and with diastereoselectivities of up to 98%. The latter undergo reductive N-N bond cleavage with BH 3 ⋅ THF and, after Nprotection with Boc 2 O or benzyl bromide, afford N-protected β-amino sulfones with moderate to high enantiomeric excesses (ee = 42 to Ն96%) without racemization. Subsequent α-