Remarkably, even a highly hindered t Bu-substituted electrophile gave products 54 and 55 under standard conditions with >99% ee. To investigate the rationale behind high enantio-and regioselectivity, we carried out computational studies of the catalytic cycle and competing transition structures (TSs). Experimentally, rapid transmetalation is observed between Rh(I) and arylboronic acids , and so our calculations start from the Rh-aryl complex [Rh], along with dimethyl phosphonate for conformational simplicity.