Halophenol Rearrangement in Lewis Acid-Catalyzed Friedel–Crafts Conditions: Evidence of Competitive Initial Protonation and Acylation

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Contents Vol 61(10)

doi:10.1071/CH08084

Halophenol Rearrangement in Lewis Acid-Catalyzed Friedel–Crafts Conditions: Evidence of Competitive Initial Protonation and Acylation

Koushik Saha ^A, Nordin H. Lajis ^A ^B ^E, Faridah Abas ^A ^C, Nabil Ali Naji ^A, A. Sazali Hamzah ^D, Khozirah Shaari ^A ^B

^A Laboratory of Natural Products, Institute of Bioscience, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
^B Department of Chemistry, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
^C Department of Food Science, Faculty of Food Science and Technology, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
^D Department of Chemistry, Faculty of Applied Science, University of Technology Mara, 40450 Shah Alam, Selangor, Malaysia.
^E Corresponding author. Email: nhlajis@ibs.upm.edu.my





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Australian Journal of Chemistry 61(10) 821–825 http://dx.doi.org/10.1071/CH08084
Submitted: 27 February 2008 Accepted: 12 August 2008 Published online: 6 October 2008

Abstract

Halogen rearrangement was observed during the Lewis acid-catalyzed Friedel–Crafts reaction of phthalic anhydride with bromophenols or bromoanisole. Further investigation revealed that 2-, 3-, and 4-bromophenols undergo rearrangement into other isomers under these reaction conditions. Product distribution from these reactions suggested that halogen rearrangement takes place during the s-complex intermediate of the condensation step. Furthermore, iodophenol undergoes hydrodeiodination rapidly rather than rearrangement, whereas chlorophenol does not undergo rearrangement at all.