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Multicomponent Condensation Reactions via ortho-Quinone Methides

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journal contribution
posted on 30.03.2017, 12:08 by Emily E. Allen, Calvin Zhu, James S. Panek, Scott E. Schaus
Iron­(III) salts promote the condensation of aldehydes or acetals with electron-rich phenols to generate ortho-quinone methides that undergo DielsAlder condensations with alkenes. The reaction sequence occurs in a single vessel to afford benzopyrans in up to 95% yield. The reaction was discovered while investigating a two-component strategy using 2-(hydroxy­(phenyl)­methyl)­phenols to access the desired ortho-quinone methide in a DielsAlder condensation. The two-component condensation also afforded the corresponding benzopyran products in yields up to 97%. Taken together, the two- and three-component strategies using ortho-quinone methide intermediates provide efficient access to benzopyrans in good yields and selectivities.