Silica Sulfuric Acid/ NaNO2 as a Novel Heterogeneous System for the Nitration of Phenols under Mild Conditions

Abstract

Nitrophenols can be obtained in moderate to high yields via nitrosation-oxidation of phenols with silica sulfuric acid, NaNO2 and wet SiO2 at room temperature. In situ generation of HNO2 and a radical cation mechanism via the nitrous acid catalyzed (NAC) pathway appear to be applicable to phenol nitration using these reagents.

Advances in science and technology of modern energetic materials: An overview

“…Application of inorganic nitrates such as bismuth nitrate [112,113] [Bi(NiO 3 ) 3 ], cerium ammonium nitrate [114] (CAN), sodium nitrite [115] (NaNO 2 ) and potassium nitrate (KNO 3 ) as nitrating agent were found to be more useful for nitration of aromatic compounds using silica gel as a solid support. Badgujar et al [116] recently reported the environmentally benign synthesis of aromatic nitro compounds using silica supported inorganic nitrates. This is an important step towards eco-friendly nitration process.…”

Environmentally compatible next generation green energetic materials (GEMs)

“…Application of inorganic nitrates such as bismuth nitrate [Bi(NiO 3 ) 3 ] [90,91], cerium ammonium nitrate [92], sodium nitrite (NaNO 2 ) [93] and potassium nitrate (KNO 3 ) [94] as nitrating agent were found to be more useful for nitration of aromatic compounds using silica gel as a solid support. These new nitrating systems will drastically reduce the use of acid in the nitration system, which will be an added advantage in terms of green and eco-friendly process.…”

Catalytic effects of some Keggin-type heteropoly acids and polyoxometalates on selective nitration of phenols

“…These problems have encouraged the search for other methods, especially alternating catalytic amounts of various solid acids with stoichiometric amounts of corrosive Brönsted acids and various nitrates or nitrites with nitric acid. Some of these methods include AcONO 2 [5], TfONO 2 [6], NaNO 3 /HCl with catalytic amounts of La(NO 3 ) 3 [7], trichloroisocyanoric acid/NaNO 2 /wet SiO 2 [8], Bi(NO 3 ) 3 .5H 2 O [9], Bi(NO 3 ) 3 /montmorillonite KSF [10], NaNO 3 /wet SiO 2 [11] , NaNO 2 /silica sulfuric acid [12], Mg(NO 3 ) 2 .6H 2 O [13], Cu(NO 3 ) 2 /clay [14], Fe(NO 3 ) 3 /clay [15], Fe(NO 3 ) 3 .9H 2 O/ionic liquid [16], VO(NO 3 ) 3 [17], some other metal nitrate/clay combinations activated by acetic anhydride [18], and more recently, ultrasound promoted nitration in ionic liquid with ferric nitrate and clayfen with good para selectivity [19], calcium nitrate/microwave [20], zirconyl nitrate [21] and PTSA/Ni(NO 3 ) 3 [22].…”