Molybdenum(II)-Catalyzed Allylation of Electron-Rich Aromatics and Heteroaromatics.

The stable, readily available molybdenum(II) complexes [Mo(CO)(4)Br(2)](2) (B) and Mo(CO)(3)(MeCN)(2)(SnCl(3))Cl (C) have been found to catalyze C-C bond-forming allylic substitution with electron-rich aromatics (e.g., 15 + PhOMe --> 62) and heteroaromatics (e.g., 15 + 36 --> 88) as nucleophiles under mild conditions (room temperature, 30 min-3 h). Remarkable is the para-selectivity for anisole, whereas phenol tends to favor ortho-substitution in certain instances. Mechanistic and stereochemical experiments are indicative of Lewis-acid catalysis rather than a metal template-controlled process.