Copper-Catalyzed, Stereoselective Cross-Coupling of Cyclic Allyl Boronic Acids with α‑Diazoketones WangDong SzabóKálmán J. 2017 In this study, we present the synthesis of new, stereodefined allylboronic acids employed to investigate the stereochemistry of the Cu-catalyzed cross-coupling of allylboronic acids with α-diazoketones. According to our results, this reaction proceeds with retention of the relative configuration of the allylboronic acid substrate. We suggest that the stereoinduction step involves a <i>syn</i> S<sub>E</sub>2′-type transmetalation of the allylboronic acid substrate with a Cu–carbene species.