An unprecedented umpolung spirocyclopropanation reaction of -quinone methides and α-keto carbonyls is described. Our umpolung strategy based on 1,6-conjugate addition and intramolecular nucleophilic substitution offers a new method for effective access to a series of highly functionalized spirocyclohexadienonyl cyclopropanes having two vicinal quaternary carbons in ≤98% yield and >20:1 dr. Significantly, cyclic and acyclic topological structures of α-keto carbonyls as 1,1-dipole one-carbon synthons have a distinct influence on the stereochemistry of products, showing a reversal of diastereoselectivity in this P(NMe)-mediated umpolung spirocyclopropanation.
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http://dx.doi.org/10.1021/acs.orglett.0c02998 | DOI Listing |
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