Efficient Synthesis of Novel Bridgehead-Substituted Bicyclo[3.2.1]octane-2,4-diones

Abstract

We report the efficient synthesis of bridgehead-substituted bicyclo[3.2.1]octane-2,4-diones. The key step in their construction is a highly efficient intramolecular [3+2] cycloaddition between a nitrile oxide and an olefin. The reductive ring cleavage of the resulting dihydroisoxazole provides the desired bridgehead-­substituted bicyclo[3.2.1]octane-2,4-diones.

Key words

thioacetals - umpolung - heterocycles - Michael addition - bicyclic compounds

References and Notes

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15

Compounds 7, 18, and 19 exist preferentially in the diketone form in CDCl₃, as observed by ^¹H NMR. However, in a more polar solvent system (CDCl₃-CD₃OD, 10:1) two isomeric keto-enol tautomers are observed for compound 20 (see Supporting Information for details).