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Convergent Synthesis of 2H-Chromenes - a Formal [3+3] Cycloaddition by a One-pot, Three-Step Cascade |
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| Authors: | Parker Kathlyn A Mindt Thomas L |
| Affiliation: | a Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794, USA b Department of Chemistry, Brown University, Providence, RI 0291, USA c Division of Radiological Chemistry, University of Basel and University Hospital Basel, 4031 Basel, Switzerland |
| Abstract: | In cases in which the palladium-catalyzed coupling of a bromoquinone with a vinyl stannane affords a vinyl quinone that enolizes, the resulting ortho-quinone methide undergoes an oxa-6π electrocyclization. Enolization is promoted by the presence of a polar additive. The net conversion is a formal [3+3] cycloaddition that gives 2H-chromenes. Because the first two steps of the cascade are catalyzed, the overall conversion is an example of multicatalysis. Yields for the optimized, one-pot protocol are dramatically improved over the conventional stepwise process. |
| Keywords: | Electrocyclization Cascade ortho-Quinone methide Stille coupling Formal [3+3] cycloaddition |
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