Regioselective C–H Alkylation of Aromatic Ethers with Alkenes by a Half-Sandwich Calcium Catalyst

The catalytic ortho-regioselective C–H alkylation of a variety of alkoxy-substituted benzene derivatives with alkenes can be achieved by the use of a half-sandwich calcium alkyl complex [(CpAr5)­Ca­{CH­(SiMe3)2}­(THF)] (2) (CpAr5 = C5Ar5, Ar = 3,5-iPr-C6H3) as the precatalyst. The potential catalytic reaction intermediates, half-sandwich calcium anisyl complexes [(CpAr5)­Ca­(o-MeO-m-Ph-C6H3) (THF)2] (8) and [(CpAr5)­Ca­(o-MeO-2-Np) (THF)2] (9) (Np = naphthyl), were isolated and X-ray structurally characterized. DFT calculations were carried out to elucidate the different reaction profiles of sp2 and sp3 C–H activations.