RADICAL-CATION CATALYSIS IN THE SYNTHESIS OF DIPHENYLMETHANES VIA THE DEALKYLATIVE COUPLING OF BENZYLIC ETHERS

The dealkylative coupling of benzyl alkyl ethers (ArCH(2)OR) to yield the corresponding diarylmethanes (ArCH2Ar) together with dialkoxymethane (ROCH(2)OR) is catalyzed by small amounts of 1-electron oxidants (such as aromatic cation radicals, NO+, etc.) or py an equivalent electrochemical (anodic) method. The catalytic method is successfully employed for the facile synthesis of a novel macrocyclic crown ether 18 that contains a diarylmethane linkage. On the basis of the spectral observation of the radical cation ArCH(2)OR(.+) and the excellent catalytic efficiency with turnover numbers in excess of 10(2), an electron-transfer and an alternative electrophilic chain mechanism are discussed for the dealkylative coupling process.