Stabilization of ortho-quinone methides by a bis(sulfonium ylide) derived from 2,5-dihydroxy-[1,4]benzoquinone |
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Authors: | Anjan Patel Thomas Rosenau |
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Institution: | a BOKU University, Department of Chemistry, Muthgasse 18, A-1190 Vienna, Austria b Research and Development, DSM Nutritional Products, PO Box 3255, CH-4002 Basel, Switzerland |
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Abstract: | The zwitterionic intermediates (2a) in the oxidation of ortho-alkylphenols (1) and bis(sulfonium ylide) 3 form reasonably stable 2:1-complexes (4), in which the ortho-quinone methide (oQM) moieties are not present in quinoid form with the exocyclic in-plane methylene group, but as zwitterionic, aromatic conformer having an out-of-plane exocyclic methylene group. The complex 7 derived from the α-tocopherol model compound PMC (5) was comprehensively characterized. As exemplarily demonstrated, the adducts can be advantageously employed in organic synthesis as ‘stabilized oQMs’. |
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Keywords: | ortho-Quinone methides ortho-Alkylphenols Aromaticity Sulfonium ylides Zwitterions |
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