- Cerium photocatalyzed radical smiles rearrangement of 2-aryloxybenzoic acids
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We report herein a cerium photocatalyzed aryl migration from an aryl ether to a carboxylic acid group through radical-Smiles rearrangement. This operationally simple protocol utilizes inexpensive CeCl3as a photocatalyst and converted a variety of 2-aryloxybenzoic acids into aryl-2-hydroxybenzoates in good yields.
- Tripathy, Alisha Rani,Yatham, Veera Reddy,Yedase, Girish Suresh
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p. 25207 - 25210
(2021/08/05)
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- A photoredox-neutral Smiles rearrangement of 2-aryloxybenzoic acids
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We report on the use of visible light photoredox catalysis for the radical Smiles rearrangement of 2-aryloxybenzoic acids to obtain aryl salicylates. The method is free of noble metals and operationally simple and the reaction can be run under mild batch or flow conditions. Being a redox neutral process, no stoichiometric oxidants or reductants are needed.
- Gonzalez-Gomez, Jose C.,Ramirez, Nieves P.,Lana-Villarreal, Teresa,Bonete, Pedro
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p. 9680 - 9684
(2017/11/30)
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- Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To Form an Ester by Visible-Light Photoredox Catalysis
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We have developed a highly efficient aryl migration from an aryl ether to a carboxylic acid group through retro-Smiles rearrangement by visible-light photoredox catalysis at ambient temperature. Transition metals and a stoichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C?O bond cleavage, we developed a novel approach to the C?O cleavage of a biaryl ether to form two phenolic compounds, as demonstrated by a one-pot, two-step gram-scale reaction under mild conditions. The aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds, such as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by a reductive quenching pathway.
- Wang, Shao-Feng,Cao, Xiao-Ping,Li, Yang
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supporting information
p. 13809 - 13813
(2017/10/24)
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- Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions
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Flash vacuum pyrolysis (FVP) of aryl 2-(allyloxy)benzoates 5 and of the corresponding aryl 2-(allylthio)benzoates 6 at 650°C, gives dibenzofurans 19 and dibenzothiophenes 20, respectively. The mechanism involves generation of phenoxyl (or thiophenoxyl) radicals by homolysis of the O-allyl (or S-allyl) bond, followed by ipso attack at the ester group, loss of CO2 and cyclisation of the resulting aryl radical. Synthetically, the procedure works well for p-substituted substrates, which lead to 2-substituted dibenzofurans 19b-f (73-90%) and dibenzothiophenes 20b-c (90-94%). Little selectivity is shown in the cyclisation of m-substituted substrates and competing interactions of the radical with the substituent - and ipso-attack - complicate the pyrolyses of o-substituted substrates. FVP of related radical precursors including 2-(allyloxy)phenyl benzoates 43 gave no dibenzofurans, whereas 2-(allyloxy-5-methyl)azobenzene 44 gave a much reduced yield. No carbazoles were obtained by FVP of 4-methylphenyl 2-(allylamino)benzoate 42.
- Black, Michael,Cadogan,McNab, Hamish
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experimental part
p. 2961 - 2967
(2010/09/06)
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