Electrochemical oxidation of aromatic ethers. Part 9. Proof of the mode of aryl–aryl coupling in 4-benzylisochroman-3-ones, and the oxidative reactions of 2-and 3-aralkyl-1,2,3,4-tetrahydroisoquinolines

Abstract

The influence of the solvent upon the coupling reactions of 4-(3,4-dimethoxybenzyl)-6,7-dimethoxy-isochroman-3-one has been studied and it is shown that formation of the product, 7a,8-dihydro-3,10,11-trimethoxy-2H-phenanthro[9,8a-b]furan-2,7(5H)-dione, proceeds through a six-membered ring transition state. Anodic oxidation of 2-aralkyl-1,2,3,4-tetrahydroisoquinolines leads to cleavage of the aralkylsubstituent, whereas 1,2,3,4-tetrahydro-6,7-dimethoxy-3-(3,4-dimethoxybenzyl)-2-methyl-isoquinoline cyclises to yield 1,2,3,4-tetranydro-7,10,11-tirimethoxy-3-methyl-2,8a-methanodiben-zo[c, e]azocin-6-one and its 1-hydroxy derivative.