Asymmetric SN2′-type C-H functionalization of arenes with propargylic alcohols

Herein we present the first example of transition metal-mediated stereodefined beta-OH elimination, an atom economical [(CpRhCl2)-Rh-star](2)-catalyzed S(N)2'-type coupling between easily available arenes and non-terminal tertiary 2-alkynylic alcohols at rt affording fully substituted allenes with H2O as the only by-product. When optically active propargylic alcohols were used, asymmetric allenylation was realized with perfect chirality transfer. It is unveiled that the reversed regioselectivity for the C-C triple bond insertion is induced by the steric effect of the tertiary carbon center as well as the weak coordination nature of the hydroxyl oxygen with Rh, which is also responsible for the stereospecificity of the rather uncommon beta-OH elimination forming allenes.