Mononitration of phenol derivatives by guanidinium nitrate and silica sulfuric acid under mild conditions Arash Ghorbani-Choghamarani * , Hamid Goudarziafshar, Mohsen Nikoorazm, Zahra Naseri Department of Chemistry, Faculty of Science, Ilam University, P.O. Box 69315516, Ilam, Iran Received 9 May 2011 Available online 13 October 2011 Abstract A mixture of guanidinium nitrate and silica sulfuric acid acts as mild and heterogeneous media for the efficient mono nitration of phenolic compounds in dichloromethane at room temperature. # 2011 Arash Ghorbani-Choghamarani. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Nitration; Phenol; Heterogeneous; Guanidinium nitrate; Silica sulfuric acid The replacement of current chemical processing techniques with more environmentally benign alternatives is an increasingly attractive subject [1]. Electrophilic aromatic substitution reactions are of considerable importance in the production of fine chemicals [2]. Nitration of organic substrates is a widely studied reaction of great industrial significance as many nitro-compounds are extensively utilized and act as intermediates for the manufacture of plastics, dyes, perfumes, drugs and pharmaceuticals [3]. Nitrophenols are very important organic intermediates and hence it is still interesting to develop regiospecific pollution-free nitrating procedures for phenolic compounds under mild conditions [4]. Traditionally, procedures for the nitration of phenolic compounds have applied a mixture containing concentrated nitric acid and sulfuric acid, which have a lot of disadvantageous including harsh conditions, low selectivity and difficulties in handling. Various nitrating reagents or reagent systems for the nitration of phenols have been emerged in the last decade such as WO 3 –HNO 3 [2], Zeolite H–Y-supported copper(II) nitrate [5], TiO 2 –[Ti 4 H 11 (PO 4 ) 9 ]ÁnH 2 O/HNO 3 [6], ([bmim][HSO 4 ])–NaNO 3 [7], Yb–Mo–HKSF–HNO 3 [8], TBAB/HNO 3 [9], M(NO + ) n ÁxH 2 O/PTSA [10], Mg(HSO 4 ) 2 or NaHSO 4 /NaNO 3 [11], Bi(NO 3 ) 3 Á5H 2 O [12], nitric acid/zinc chloride [13] and Bi(NO 3 ) 3 Á5H 2 O/ HNO 3 [14]; but many of these methods suffer from some drawbacks, including low selectivity, tedious work-up, toxicity, un-degradable reagents and catalyst and long reaction times. Therefore, we decided to overcome mentioned limitations by introducing of an environmentally friendly procedure for the preparation of nitrophenols. In continuation of our studies on the designing of new systems for the organic functional group transformations [15–27] we became interested to design a metal-free, green and heterogeneous media for the production of mono nitrated phenol derivatives. Recently we have introduced a catalytic method for the selective oxidation of sulfides into www.elsevier.com/locate/cclet Available online at www.sciencedirect.com Chinese Chemical Letters 22 (2011) 1431–1434 * Corresponding author. E-mail addresses: arashghch58@yahoo.com, a.ghorbani@mail.ilam.ac.ir (A. Ghorbani-Choghamarani). 1001-8417/$ – see front matter # 2011 Arash Ghorbani-Choghamarani. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2011.07.012