221344-96-3Relevant 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 (2007/10/03)
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.
Asymmetric synthesis of α-substituted β-amino sulfones by aza-Michael addition/α-alkylation
Enders, Dieter,Müller, Stephan F.,Raabe, Gerhard
, p. 741 - 743 (2007/10/03)
The aza-Michael addition of (S)-1-amino-2-methoxymethyl-pyrrolidine (SAMP) to alkenyl sulfones (E)-1, followed by reductive N-N bond cleavage with BH3 · THF and N-benzylation yields N-benzyl-protected β-amino sulfones (R)-3 with high enantiomeric excesses (ee≥96%). Subsequent α- alkylation of (R)-3 with various electrophiles leads to α-alkyl-β-amino sulfones (R,R)-4a-e in excellent yields (88-97%) and finally high diastereomeric (de = 96-≥98%) and enantiomeric purity (ee≥96%). The absolute configuration was determined by X-ray structural analysis and confirmed by NMR spectroscopy (NOE-experiments).
Efficient N-N bond cleavage of chiral trisubstituted hydrazines with BH3·THF
Enders, Dieter,Lochtman, René,Meiers, Michaela,Müller, Stephan,Lazny, Ryszard
, p. 1182 - 1184 (2007/10/03)
Cleavage of the N-N bond of chiral trisubstituted hydrazines 1 with excess BH3·THF complex gives the corresponding optically active amines 2 in moderate to excellent yields and with high enantiomeric purity. This racemization and epimerization free cleavage procedure is compatible with functionalities sensitive to reductive cleavage conditions.
