Substituent‐induced regioselective hydroxylation of the aromatic C–H bond on naphthalene with metachloroperbenzoic acid catalyzed by F20TPPMnCl

The regioselective hydroxylation of the aromatic C–H bond on a series of naphthalenes with different β‐substituent R (R = H, Me, Et, i ‐Pr, OMe, COOH, Br, etc.) was studied, and the substituent effect on the regioselectivity was investigated. The electron‐donating substituent afforded the aromatic C–H bond hydroxylation at the 1α position with more than 80% selectivity, while the electron‐withdrawing substituent afforded the aromatic C–H bond hydroxylation at the 4α position with more than 60% selectivity of β‐substituted naphthalene hydroxylated with metachloroperbenzoic acid catalyzed by tetrakis(pentafluorophenyl)porphyrin manganese(III) chloride. The research showed that the steric and electronic effects of the substituent appeared to play a significant role in determining the regioselectivity, and the electronic effect was of more importance than the steric effect of the substituent in the current situation. The studies may provide additional proofs for the stepwise mechanism of the aromatic C–H bond hydroxylation through a cationic intermediate. Copyright © 2012 John Wiley & Sons, Ltd.