Heteroatom Chemistry Volume 25, Number 2, 2014 Boric Acid as Highly Efficient Catalyst for the Synthesis of Phenols from Arylboronic Acids Kongkona Gogoi, 1 Anindita Dewan, 1 Ankur Gogoi, 1 Geetika Borah, 1 and Utpal Bora 1,2 1 Department of Chemistry, Dibrugarh University, Dibrugarh 786 004, Assam, India 2 Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784 028, Assam, India Received 6 June 2013; revised 26 November 2013 ABSTRACT: A simple, efficient, and environmentally benign boric acid catalyzed methodology for the ipso- hydroxylation of arylboronic acid to phenol has been developed using aqueous hydrogen peroxide as an oxi- dizing agent and ethanol as the solvent. The versatility of this protocol is that the reactions were performed at room temperature in short reaction time under metal-, ligand-, and base-free conditions. C  2014 Wiley Peri- odicals, Inc. Heteroatom Chem. 25:127–130, 2014; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21138 INTRODUCTION Phenols and their derivatives are ubiquitous in nu- merous natural products in monomeric or polymeric forms. They have vast application potential as a key synthetic precursor for the construction of pharma- ceuticals, polymers, and naturally occurring com- pounds [1]. Over the years, various modifications have been made to the reaction conditions leading to novel synthetic methods for their synthesis. Phe- nols are commonly prepared by nucleophilic aro- matic substitution of aryl halides, and Cu-catalyzed Correspondence to: U. Bora; e-mail: utbora@yahoo.co.in; ubora@tezu.ernet.in. Contract grant sponsor: University Grants Commission, New Delhi, India. Contract grant number: 41-254/2012 (SR). C  2014 Wiley Periodicals, Inc. transformation of diazoarenes and benzyne proto- cols [2]. However, these methods suffer from major drawbacks such as harsh reaction conditions and di- azotization of amino groups to diazoarenes, which is often not compatible with many other functional groups. In addition to it, some literature reported the conversion of aryl halides such as aryl bromides and chlorides into phenols in the presence of Pd- based catalysts, phosphine ligands [3], and aryl io- dides into the corresponding phenols in the pres- ence of a Cu-catalyst using non-phosphine ligands [4] at high temperature. Over the last decade, aryl- boronic acids and their derivatives have emerged as an important moiety in a wide range of or- ganic reactions [5]. Although phenols have been reported as byproducts in many metal-catalyzed reactions of arylboronic acids [6], a detailed liter- ature search revealed only a handful of recent re- ports available on the direct and efficient conver- sion of arylboronic acids into phenols. Arylboronic acids are considered as a suitable and potent pre- cursor of phenols because they are safe, stable to heat, moisture, and air, and are commercially available in many forms substituted by functional groups. Accordingly, hydroxylation of arylboronic acids to phenols is reported to be feasible in the pres- ence of MCPBA–H 2 O–EtOH [7], acidic Al 2 O 3 –H 2 O 2 [8], I 2 –H 2 O 2 [9], CuSO 4 –phenanthroline [10], H 2 O 2 – poly(N-vinylpyrollidone) [11], NH 2 OH.HCl:NaOH [12], potassium peroxymonosulfate [13], or aqueous H 2 O 2 [14], clay-entrapped Cu(OH)x [15], aqueous ammonia [16], sodium chlorite [17], and tert-butyl 127