科研之友
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摘要
The regioselective hydroxylation of the aromatic CH bond on a series of naphthalenes with different beta-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 CH bond hydroxylation at the 1a position with more than 80% selectivity, while the electron-withdrawing substituent afforded the aromatic CH bond hydroxylation at the 4a position with more than 60% selectivity of beta-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 CH bond hydroxylation through a cationic intermediate.
