Synthesis of 1,2-dioxanes, 1,2,4-trioxanes, and 1,2,4-trioxepanes via cyclizations of unsaturated hydroperoxyacetals

Unsaturated hydroperoxyacetals and -ketals undergo electrophilic cyclization to afford dioxanes, trioxanes or trioxepanes. Stereoselectivity is low for trioxepanes, moderate for dioxanes, and high for trioxanes. The hydroperoxide starting materials are readily prepared through selective ozonolysis of an enol ether in the presence of an internal or external alkene.