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Quaternary ammonium hydroxide‐functionalized g‐C 3 N 4 catalyst for aerobic hydroxylation of arylboronic acids to phenols
Author(s) -
Muhammad Ibrahim,
Mannathan Subramaniyan,
Sasidharan Manickam
Publication year - 2020
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.202000141
Subject(s) - chemistry , catalysis , ammonium hydroxide , hydroxylation , hydroxide , methyl iodide , nuclear chemistry , iodide , tetrabutylammonium hydroxide , phenols , ammonium iodide , ion exchange , base (topology) , inorganic chemistry , organic chemistry , ion , mathematical analysis , mathematics , enzyme
A new and efficient metal‐free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g‐C 3 N 4 catalyst has been described. The functionalized quaternary ammonium hydroxide (g‐C 3 N 4 ‐OH) has been prepared from graphitic carbon nitride (g‐C 3 N 4 ) scaffold by converting the residual –NH 2 and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion‐exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH‐ form) by post‐synthetic modification. The resultant g‐C 3 N 4 ‐OH was characterized by XRD, FTIR, field‐emission scanning electron microscope (FESEM), high‐resolution transmission electron microscope (HRTEM), N 2 adsorption/desorption isotherms, and acid–base titration. Tested as solid‐base catalysts, the g‐C 3 N 4 ‐OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g‐C 3 N 4 ‐OH solid‐base has been successfully reused four times with the minor loss of initial catalytic activity (10.5%).