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)(SnCl3)Cl (C) have been found to catalyze C-C bond -forming allylic substitution with electron-rich aromatics (e.g., 15 + PhOM e --> 62) and heteroaromatics (e.g., 15 + 36 --> 88) as nucleophiles under mild conditions (room temperature, 30 min-3 h). Remarkable is the para-sele ctivity for anisole, whereas phenol tends to favor ortho-substitution in ce rtain instances. Mechanistic and stereochemical experiments are indicative of Lewis-acid catalysis rather than a metal template-controlled process.