233264-87-4Relevant academic research and scientific papers
Asymmetric synthesis of α-substituted β-amino sulfones by aza-Michael addition to alkenyl sulfones and subsequent α-alkylation
Enders, Dieter,Müller, Stephan Frank,Raabe, Gerhard,Runsink, Jan
, p. 879 - 892 (2000)
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 BH3 · THF and, after N- protection with Boc2O or benzyl bromide, afford N-protected β-amino sulfones with moderate to high enantiomeric excesses (ee = 42 to ≥96%) without racemization. Subsequent α-alkylation of the N,N-dibenzyl protected β-amino sulfones with various electrophiles yields α-alkyl-β-amino sulfones in excellent yields (88-97%) with high diastereomeric (de ≥96 to ≥98%) and enantiomeric purity (ee = 94 to ≥96%). The absolute configuration of the new stereogenic centre was determined by X-ray structural analysis and confirmed by NMR spectroscopy (NOE experiments). Possible reaction mechanisms for the conjugate addition and α-alkylation are presented.
