Successive Michael Reaction-Sigmatropic Rearrangement of Polyquinones with Silyl Ketene Acetals

Michael-type additions of polyquinones such as quinizarinquinone (1) and naphthodiquinone (2) with various O-silylated ketene acetals followed by successive sigmatropic rearrangements of the adducts are described. The Michael-type additions of the O-silylated ketene acetals with the highly electrophilic polyquinones took place exclusively at the internal double bond without any catalysts. Some of the resultant adducts performed interesting rearrangements under thermal or Lewis acid conditions to give external adducts that are obtained formally by the addition to polyquinones at the less reactive external double bond.