Synthesis and acid-catalyzed transformations of solvomercuration adducts of 2-nitrobenzylcyclopropane. First stable metalated 1-oxo-3,4-dihydro-1H-2,1-benzoxazinium ions

Sovomercuration adducts of 2-nitrobenzyl-, 2-nitro-4,5-(ethylenedioxy)benzyl-, and 4,5-dimethoxy-2-nitrobenzylcyclopropanes were synthesized. The adducts reacted with sulfuric, fluorosulfonic, or chlorosulfonic acid to give 3-(2-chloromercurio)ethyl-1-oxo-3,4-dihydro-1H-2,1-benzoxazinium ions whose stability depended on the nature of substituents in the aromatic ring. Unstable metalated 1-oxo-3,4-dihydro-1H-2,1-benzoxazinium ions underwent fast protodemercuration to form metal-free 3-ethyl-1-oxo-3,4-dihydro-1H-2,1-benzoxazinium ions. Stable analogs in the above acids did not change to an appreciable extent over a period of 48–72 h. Hydrolysis of stable metalated 1-oxo-1,3-dihydro-2,1-benzoxazolium ions afforded only 4-chloromercurio-1-(2-nitroaryl)butan-2-ol.