Copper-Catalyzed Asymmetric Acylboration of 1,3-Butadienylboronate with Acyl Fluorides

We report herein a Cu-catalyzed regio-, diastereo- and enantioselective acylboration of 1,3-butadienylboronate with acyl fluorides. Under the developed conditions, the reactions provide (Z)-& beta;,& gamma;-unsaturated ketones bearing an & alpha;-tertiary stereocenter with high Z-selectivity and excellent enantioselectivities. While direct access to highly enantioenriched E-isomers was not successful, we showed that such molecules can be synthesized with excellent E-selectivity and optical purities via Pd-catalyzed alkene isomerization from the corresponding Z-isomers. The orthogonal chemical reactivities of the functional groups embedded in the ketone products allow for diverse chemoselective transformations, which provides a valuable platform for further derivatization. A Cu-catalyzed regio-, diastereo- and enantioselective acylboration of 1,3-butadienylboronate with acyl fluorides is shown. The reaction provided (Z)-& beta;,& gamma;-unsaturated ketones bearing an & alpha;-tertiary stereocenter with high Z-selectivity and excellent enantioselectivities. Highly enantioenriched (E)-& beta;,& gamma;-unsaturated ketones can also be obtained with excellent E-selectivity via Pd-catalyzed alkene isomerization from the corresponding Z-isomers.+image