Biomimetic flavin organocatalysts oxidize nitromethane to formaldehyde and NO x providing a relatively nontoxic, noncaustic, and inexpensive source for catalytic NO 2 for aerobic TEMPO oxidations of alcohols, diols, and ethers. Alcohols were oxidized to aldehydes or ketones, cyclic ethers to esters, and terminal diols to lactones. In situ trapping of NO x and formaldehyde suggest an oxidative Nef process reminiscent of flavoprotein nitroalkane oxidase reactivity, which is achieved by relatively stable 1,10-bridged flavins. The metal-free flavin/NO x /TEMPO catalytic cycles are uniquely compatible, especially compared to other Nef and NO xgenerating processes, and reveal selectivity over flavin-catalyzed sulfoxide formation. Aliphatic ethers were oxidized by this method, as demonstrated by the conversion of (−)-ambroxide to (+)-sclareolide.