TETRAHEDRON LETTERS Pergamon Tetrahedron Letters 40 (1999) 2859-2862 Fe(III) Exchanged Montmorillonite: A Mild And Eco- friendly Catalyst For Sulfonylation Of Aromatics B.M. Choudary', N. Sreenivasa Chowdari, M. Lakshmi Kantam and R. Kannan Indian Institute of Chemical Technology, Hyderabad 500 007, lndia. Received 30 November 1998; accepted 9 February 1999 Abstract: Fe(III) exchanged montmorillonite clay catalyses Friedel-Crafts sulfonylation of arenes with arylsulfonyl chlorides to obtain the corresponding sulfones in excellent yields. © 1999 Published by Elsevier Science Ltd. All rights reserved. Keywords: Suffonylation"Montmorillonite" Arenes- Sulfones. The increasing demand for cleaner processes prompted by stringent environment laws requires the use of ecofriendly and selective catalysts. The use of solid acids to replace waste generating soluble Lewis acids for the alkylation of arenes and acylation of activated arenes represent examples of improved procedures. Diaryl sulfones are synthesised using conventional Lewis acid catalysts [1-5], for example AICl3, and are useful intermediates for the drug industry. Aluminium chloride is widely used in the laboratory and industry and generates an enormous amount of solid waste. A catalytic sulfonylation method for the synthesis of diaryl sulfones using inexpensive and non-polluting reagents is highly desirable. In recent years the use of clays as catalysts and catalyst supports has received considerable attention [6-1 l]. Expandable layer lattice clays such as montmorillonites have H0 values between 1.5 and -3 and their acidities may be tuned further by metal ion exchange with the introduction of a large number of Lewis acidic sites. Acidic cation exchanged montmorillonites are found to be efficient catalysts for electrophilic aromatic substitution reactions [12-14]. We report in this letter sulfonylations by a Fe3+-montmorillonite catalyst for the first time affording high para-selectivity and excellent yields (Scheme l). Fe3+-montmorillonite clay was prepared in accordance with the literature [13]. The Fe content analysis of the catalyst was carried out according to Vogel's procedure [15] and foundto be *Fax: 0091 40 7173387: E-mail: iict(~, ap.nic.in; IICT Communication No.: 4194. 0040-4039/99/$ - see front matter © 1999 Published by Elsevier Science Ltd. All tights reserved. PH: S0040-4039(99)00312-3