Highly Stereoselective Benzylation of <i>N</i>-Sulfinylketimines
2005-09-21T00:00:00Z (GMT) by
The benzylation of <i>N</i>-sulfinyl ketimines with 2-(<i>p</i>-tolylsulfinyl)ethylbenzene and LDA afford <i>t</i>-alkylamines in good yields. The configuration at each one of the new chiral centers simultaneously created in this reaction is controlled by the configuration of the sulfinyl groups at the nucleophile and electrophile, respectively. Thus, the reactions of the (<i>S</i>)-sulfoxide <b>6 </b>with the <i>N</i>-(<i>S</i>)-sulfinylketimines <b>3</b> only yield the <i>anti</i> diastereoisomers <b>18</b>, whereas the <i>syn</i> diastereoisomers <b>19 </b>are exclusively formed in reactions of (<i>S</i>)-<b>6</b> with <i>N</i>-(<i>R</i>)-sulfinylketimines <b>3</b>. After a two-step desulfinylation process ((i) TFA, (ii) Ra−Ni), this reaction provides a procedure for synthesizing any epimer of α,α-dibranched β-alkylarylamines in optically pure form by choosing the configuration of the starting materials. A similar behavior is observed for carbanions derived from the O-protected 2-(<i>p</i>-tolylsulfinyl) benzyl alcohol <b>7 </b>thus allowing the synthesis of the optically pure <i>anti</i>- and <i>syn</i>-1,2-amino alcohols containing a chiral quaternary carbon adjacent to the nitrogen.