Tandem glycol cleavage—intramolecular 4+2 cycloadditions mediated by Mn(OAc)3

The Mn(OAc)3 mediated oxidative cleavage of 1 and 2 proceeded as expected, while molecular diversity was generated upon cleavage of their unsaturated counterparts 5 and 6 via a tandem glycol cleavage/4+2 process. Minor products of the reaction were identified as the α-dicarbonyl derivative (i.e. 25) and the corresponding cross-conjugated hydroxy dienone (i.e. 26). The process tolerates a variety of substitution patterns and protecting groups. A brief comparison with the Pb(OAc)4 initiated cascade transformations is presented.