The aim of this account is to present the latest findings from studies of the reactions of polynitromethanes with unsaturated compounds and oxiranes, and to review how these processes have been used in the synthesis of highly functionalized nitro compounds and nitrogen-and oxygen-containing heterocycles. In addition, literature on unstable acyclic nitronic esters, key intermediates in the tandem, multicomponent heterocyclization reactions of strained olefins, electrophilic alkenes, acetylenes, and oxiranes, is analyzed.