Convenient route to centro-substituted triquinacene skeletons via the interrupted Nazarov reaction

Readily available [4 + 3]-cycloadducts derived from trapping of the Nazarov 2-oxidocyclopentenyl cation with 2,3-dimethyl-1,3-butadiene are cleaved by ozonolysis to furnish triketones. In the presence of methanolic KOH, these triones undergo tandem aldol additions to furnish centro-hydroxylated triquinacene skeletons.