Stereo‐ and Regiochemical Divergence in the Substitution of a Lithiated Alk‐1‐en‐3‐yn‐2‐yl Carbamate: Synthesis of Highly Enantioenriched Vinylallenes or Alk‐3‐en‐5‐yn‐1‐ols

Alternative outcomes . The regio‐ and stereoselectivity of the hydroxyalkylation of a lithiated alk‐1‐en‐3‐yn‐2‐yl carbamate such as ( S )‐ 1 can be controlled simply for the synthesis of highly enantioenriched vinylallenes 2 . Alternatively, lithium–titanium exchange proceeds with inversion of configuration, and addition of carbonyl electrophiles produces enantioenriched homoaldol products such as ( S , Z )‐ 3 (see scheme, Cb=carbamoyl).