Lanthanide(III) complexes of aromatic sulfonic acids as catalysts for the nitration of toluene

Abstract

Ytterbium(III) complexes of benzenesulfonic acid, Yb(BSA) 3 , p-toluenesulfonic acid, Yb(Tos) 3 , and 2-naphthalenesulfonic acid, Yb(NSA) 3 , were prepared and tested as possible catalyst for the nitration of toluene. With a loading of 5-10 mol% of Yb(BSA) 3 and Yb(NSA) 3 , a quantitative conversion of toluene to nitrotoluene was achieved within 5 h, while Yb(Tos) 3 was slightly less active and 77% of nitrated products were obtained. The catalysts can be easily recovered after the reaction, and 1 H NMR spectroscopy of analogous diamagnetic lanthanide(III) catalysts showed that the recovered catalysts were identical to the freshly prepared ones. The ratio of ortho:meta:para products was in all reactions 52:6:42, which is consistent with a direct electrophilic attack by the nitronium ion, NO 2 + .

Lanthanide(III) Tosylates as New Acylation Catalysts

“…In pursuit of lanthanide(iii) catalysts that would not require the use of hazardous or costly compounds, we recently examined lanthanide(iii) salts of noncorrosive aromatic sulfonic acids, such as p-toluenesulfonic acid and nitrobenzenesulfonic acids, as catalysts for the nitration of aromatic compounds. [18][19][20] The aromatic sulfonic acids are much weaker acids than triflic acid, (p-toluenesulfonic acid, for example, is about 10 6 times weaker acid than triflic acid), [21] and their complexes with lanthanides would therefore be expected to be significantly weaker Lewis acids than the lanthanide(iii) triflates. Surprisingly, we found that their catalytic efficiency was comparable to that of the triflate salts.…”

Lanthanide(III) Nitrobenzenesulfonates as New Nitration Catalysts: The Role of the Metal and of the Counterion in the Catalytic Efficiency

“…[12] We recently reported that lanthanide() salts of p-toluenesulfonic acid efficiently catalysed the conversion of toluene to nitrotoluene, but they were not very effective in the nitration of aromatic compounds with electron-withdrawing groups. [13] In an attempt to increase the activity of the catalyst we also explored lanthanide() salts of pnitrobenzenesulfonic acid, which are also called lanthanide() nosylates. [14] Both p-toluenesulfonic and p-nitrobenzenesulfonic acids have some major advantages compared to triflic acid, because they are non-corrosive and much cheaper to obtain.…”

Improved Regioselective Mononitration of o-Xylene over HBEA-500 Zeolite Catalyst

“…Smith and coworks have utilized zeolites to enhance the para-selectivity in chlorination, 8 acylation, 9 and methanesulfonylation 10 of simple aromatic substrates. The present investigation was to develop a mild, easy to operate and efficient catalyst [11][12][13][14] without involving sulfuric acid and some progress has been achieved. 4-and 3-Nitro-o-xylenes are used as intermediates for the production of vitamins, fragrances, agrochemicals, dyes, etc.…”