Stereoselective Synthesis Of Trisubstituted Vinylboronates From Ketone Enolates Triggered By 1,3-Metalate Rearrangement Of Lithium Enolates

An unprecedented stereoselective synthesis of tri-substituted vinylboronates is reported to proceed by direct borylation of lithium ketone enolates under transition-metalfree conditions. The stereospecific CO borylation of lithium enolates was triggered by a carbonyl-induced 1,3-metalate rearrangement via a C-bound boron enolate. DFT calculations and control experiments revealed that the stereoselectivity is controlled by sterics. A variety of stereospecific trisubstituted vinylboronates, together with several tetrasubstituted vinylboronates, were conveniently synthesized with the newly developed methodology. Based on the transformation of stereospecific vinylboronate, a single isomer of Dienestrol was efficiently obtained.