Highly Regioselective Oxybromination in an Aqueous System Using SBA‐15 Supported Sulfated Zirconia Catalyst

Abstract

SBA-15 supported sulfated zirconia (SZ) catalysts were employed in many acid-catalysis of reactions under mild condition because it is a strong solid acid with various Lewis and Brønsted acid sites. An oxybromination of aromatic substrates using hydrogen peroxide and ammonium bromide in the aqueous phase under mild temperature and near-neutral pH condition over SZ was achieved. A good to excellent para-selectivity was observed. The mesoporous silica SBA-15 supported SZ possessed higher catalytic activity than self-supported SZ because of larger surface area and pore size. The effect of the calcinations temperature was also investigated. The good catalytic performance of the SZ/SBA-15 materials was attributed to high degree of dispersion of sulfate groups to give sulfated silica-zirconia of (1) very good redox property and (2) high strength and high density of acid sites. The SZ/SBA-15 catalyst may be re-used several times without substantial loss of activity.

Synthesis of new zirconium complex supported on MCM‐41 and its application as an efficient catalyst for synthesis of sulfides and the oxidation of sulfur containing compounds

“…Silica mesoporous molecular sieves have specific advantages, including ease of preparation, low cost, excellent thermal and chemical stability, large internal surface area and high concentration of surface Si–OH groups . MCM‐41 is member of mesoporous molecular sieves with hierarchical structure and hexagonally packed arrays that can be used as catalyst supports . These nanoparticles, because of their high surface area and good catalytic activity and high efficiency, have a wide range of applications in the removal of chromate and arsenate, drug delivery systems, extraction, adsorption, catalysis support and recycling of expensive homogeneous catalysts …”

A Green Protocol for the Bromination and Iodination of the Aromatic Compounds using H5IO6/NaBr and H5IO6/NaI in the Water

“…Recently, the oxidative halogenation of organic compounds by halides have emerged as an important alternative for the synthesis of such haloderivatives. [19][20][21][22][23][24][25][26][27][28][29][30] Despite the broad choice of options, however, many bromination and iodination methodologies are cumbersome, costly and harsh or involve the use of toxic heavy metals, volatile organic solvents, or elemental halogenes which are highly corrosive, toxic or self-sublimating. In addition, there are some environmental hazards with respect to handling them.…”

Functional Enzyme Mimics for Oxidative Halogenation Reactions that Combat Biofilm Formation

“…The activity and regioselectivity of the oxidative bromination (e.g., increased yield of para ‐bromophenol) depend on the number of exposed Lewis acidic metal sites on the catalyst surface that stabilize peroxo species and the Wheland intermediates . This leads to an enhanced yield of halogenated compounds through the formation of tungsten or molybdenum peroxo species, because Brønsted acidic sides are assumed to be involved in the electrophilic bromination process .…”

“…A good para ‐selectivity was found for the bromination of phenol. SBA‐15 supported sulfated zirconia had higher catalytic activities than self‐supported sulfated zirconia because of its larger surface area and pore size . The good catalytic performance of the sulfated zirconia on SBA‐15 obtained by calcination at higher temperature was attributed to the good dispersion of sulfate groups to give sulfated silica‐zirconia with efficient redox behavior and a high density of acidic sites …”