Early transition metal-catalyzed cross-coupling reaction of aryl fluorides with a phenethyl grignard reagent accompanied by rearrangement of the phenethyl group

Defluorination of 1-fluoronaphthalene was catalyzed by CpTiCl3 and an alkyl Grignard reagent system. The reaction of 1-fluoronaphthalene, however, with 3 equiv of phenethylmagnesium chloride in the presence of a catalytic amount of transition metal catalysts afforded 1-(1-phenethyl)naphthalene in good yield via isomerization of the phenethyl group. Among the examined catalysts, CpTiCl3 and TaCl5 showed much higher activity than the others. The similar coupling reactions of phenethylmagnesium chloride with substituted fluoroarenes proceeded with high regioselectivity at the para-position to produce the corresponding 1-phenethylarenes in good yields.