Trifluoromethanesulfonic Acid-Mediated Reaction of 2-Methoxyacetic Acid
with Arenes--Clarification of Reaction Behavior and Route for
Diarylmethanes and Anthracene Derivatives Formation--

Asami KAMEDA, Hiroki NISHIMORI, Satohiro OMURA, Masayuki KOIKE, Tetsuo HINO†, Takashi JOBASHI, Katsuya MAEYAMA and Noriyuki YONEZAWA*

Department of Organic and Polymer Materials Chemistry, Tokyo University of Agriculture and Technology; Koganei-shi 184-8588 Japan
† Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo; Hongo, Bunkyo-ku, Tokyo 113-8656 Japan

α-Methoxycarboxylic acids 1 undergo decarbonylative α,α-diarylation reaction with arenes 2 in the presence of phosphorus pentoxide-methanesulfonic acid mixture (P2O5-MsOH). However, 2-methoxyacetic acid (1d) shows different reaction behavior from those of other α-carboxylic acids (1). Trifluoromethanesulfonic acid (TfOH)-mediated reaction of 2-methoxyacetic acid (1d) with arenes 2 yields anthracene derivatives 10 in addition to Friedel-Crafts acylation type products and diarylmethanes 4. The reaction behavior was elucidated by estimating the influence of the kind of acidic medium and the substrate structure. Furthermore, based on the results of the reaction of the model compounds for the corresponding suspected reaction pathways, the adequacy of the pathways was evaluated. TfOH-mediated reactions of 2-methoxyacetic acid (1d) with arenes except for that with benzene (2f) proved to proceed via α-hydroxyacetophenone homologues 7 and 11, 1,1-diarylethanediol derivatives 14, and 1,2,2-triarylethanol derivative 17.


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