Next, we showed the effects of various phenol derivatives (Figure ). Although we used to 10 consider that alkoxide and phenoxide may poison iron species by their strong coordination , our recently reported Fe(III)/AlMe3/DEO (diethyl oxalate) catalytic system revealed that in the presence of AI(III), enediolate does not affect the catalytic activity of iron for C-H activation. Besides catechol, using naphthalene-1,8-diol also afforded 2 quantitatively. Using phenol in 4.0 equivalents also gave a high yield, but the sterically congested 2,6-diphenylphenol and 2,6-di-tert-butyl-4-methylphenol, which are known 15 to form bulky (ArO)2AlR reagent 26 , resulted in poor reaction efficacy. The reduced efficacy caused by steric hindrance may be ascribed to suppressing effective transmetallation, preventing them as effective base. The ineffectiveness of 2-methoxyphenol might be attributed to the occupation of the coordination fourth site of Al(III) by the additional methoxyl group, impeding the transmetallation step. Surprisingly, using 2-hydroxythiophenol yielded 2 in 87%, but thiophenol in 4 equivalents gave no reactivity. We 20 attribute this observation to variations in the affinity of 2-hydroxythiophenol and thiophenol for iron and aluminum. Pinacol used instead of catechol suppressed the reaction entirely, which might be because of the strong coordination of alkoxide towards iron.