SYNTHESIS OF SUBSTITUTED TETRAHYDRONAPHTHALENES BY MN(III), CE(IV), AND FE(III) OXIDATION OF SUBSTITUTED DIETHYL ALPHA-BENZYLMALONATES IN THE PRESENCE OF OLEFINS

The oxidation of substituted diethyl alpha-benzylmalonates (1a-m) by manganese(III) acetate in acetic acid, cerium(IV) ammonium nitrate in methanol, or iron(III) perchlorate in acetonitrile in the presence of substituted olefins 2a-u was investigated. The results are consistent with a common mechanism. It involves selective generation of malonyl radicals from high-valent metal malonyl complexes, their addition to the olefin, and competition of the adduct radical between intramolecular cyclization to produce highly functionalized tetrahydronaphthalenes (3) and oxidation by metal salt to give mainly gamma-lactones (5). Several electron-withdrawing and releasing substituents on the aromatic ring and on the olefin can be successfully used in the synthesis of 3 without olefin telomerization. The influence of metal and olefin or aromatic substituents on the homolytic addition and intramolecular aromatic substitution is discussed.