Manganese-Catalyzed Synthesis of Quaternary Peroxides: Application in Catalytic Deperoxidation and Rearrangement Reactions

Highly efficient,
selective, and direct C–H peroxidation
of 9-substituted fluorenes has been achieved using a Mn–2,2′-bipyridine
catalyst via radical–radical cross-coupling. Moreover, this
method effectively promotes the vicinal bisperoxidation of sterically
hindered various substituted arylidene-9H-fluorene/arylideneindolin-2-one
derivatives to afford highly substituted bisperoxides with high selectivity
over the oxidative cleavage of CC bond that usually forms
the ketone of an aldehyde. Furthermore, a new approach for the synthesis
of (Z)-6-benzylidene-6H-benzo­[c]­chromene has been achieved via an acid-catalyzed skeletal
rearrangement of these peroxides. For the first time, unlike O–O
bond cleavage, reductive C–O bond cleavage in peroxides using
the Pd catalyst and H2 is described, which enables the
reversible reaction to afford exclusively deperoxidized products.
A detailed mechanism for peroxidation, molecular rearrangement, and
deperoxidation has been proposed with preliminary experimental evidences.