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Article

N-Halosuccinimide/BF₃−H₂O, Efficient Electrophilic Halogenating Systems for Aromatics

Supporting Info

G. K. Surya Prakash,*^† Thomas Mathew,^† Dushyanthi Hoole,^† Pierre M. Esteves,^‡ Qi Wang,^† Golam Rasul,^† and George A. Olah*^†

Contribution from the Donald P. and Katherine B. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, and Instituto de Qumica, Departamento de Qumica Orgnica, Universidade Federal do Rio de Janeiro, Cidade Universitria CT Bloco A, 21949-900 Rio de Janeiro, Brazil

J. Am. Chem. Soc., 2004, 126 (48), pp 15770–15776

DOI: 10.1021/ja0465247

Publication Date (Web): November 12, 2004

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

†

University of Southern California.

‡

Universidade Federal do Rio de Janeiro.

, gprakash@usc.edu

Abstract

N-Halosuccinimides (NXS, 1) are efficiently activated in trifluoromethanesulfonic acid and BF₃−H₂O, allowing the halogenations of deactivated aromatics. Because BF₃−H₂O is more economic, easy to prepare, nonoxidizing, and offers sufficiently high acidity (−H₀ ≈ 12, only slightly lower than that of trifluoromethanesulfonic acid), an efficient new electrophilic reagent combination of NXS/BF₃−H₂O has been developed. DFT calculations at the B3LYP/6-311++G**//B3LYP/6-31G* level suggest that protonated N-halosuccinimides undergo further protosolvation at higher acidities to reactive superelectrophilic species capable either in the transfer of X⁺ from the protonated forms of NXS to the aromatic substrate or in forming a highly reactive and solvated X⁺ which would readily react with the aromatic substrates. Structural aspects of the BF₃−H₂O complex have also been investigated.