beta-sulfinyl alpha,beta-unsaturated carbonyl compounds from enantiomerically pure sulfenic acids

The addition of enantiopure sulfenic acids to oxoalkynes constitutes a new and efficient methodology for the synthesis of beta -sulfinyl alpha,beta -u nsaturated carbonyl compounds. Sulfenic acids 3 and 4 were generated by the rmolysis of suitable precursors and trapped in situ by oxoalkynes 5, afford ing (R-S, E)- and (S-S, E)-3-alkylsulfinyl-1-phenyl-2-propen-1-ones, 4-alky lsulfinyl-3-buten-2-ones, and 3-[(1S)-isoborneol-10-sulfinyl]-2-propen 6 an d 7 in good yields and in enantiomerically pure form after simple column ch romathography. (R-S,E)-3-[(1S)-isoborneol-10-sulfinyl]-1-phenyl-2-propen-on e (6(R)a) was involved as a heterodiene in inverse-electron-demanding Diels -Alder reactions with readily available electron-rich dienophiles 14 and 15 , corroborating in each case the sulfinyl auxiliary capability in controlli ng the stereochemical outcome of these cycloadditions. Furthermore, the add ition of methylmagnesium iodide to the carbonyl moiety of 6Ra demonstrated that the chiral sulfur atom exerts a remote stereocontrol in this reaction if assisted by the hydroxy group being part of the isoborneol substituent.