Radical Cyclization of Allyl 2-Iodophenyl Ether, N,N-Diallyl-2-iodoaniline, and 2-Iodoethanal Acetal by Means of Trialkylmanganate(II)

Article abstract of DOI:10.1246/bcsj.70.2039

Treatment of allyl 2-halophenyl ethers with tributylmanganate (n-Bu₃MnLi or n-Bu₃MnMgBr) provided dihydrobenzofuran derivatives in good yield. Indoline derivatives are also produced effectively starting from 2-iodoaniline compounds. The reaction could proceed by the following sequences: (1) formation of a radical by treatment of iodophenol or iodoaniline derivatives with tributylmanganate(II), (2) radical cyclization, and (3) recombination of radical and manganese species giving alkylmanganese(II) compound. The reaction proved to proceed in the presence of a catalytic amount of manganese(II) chloride under atmospheric oxygen. The manganese catalyzed radical cyclization could also be applied to 2-iodoethanal acetal, in which case the presence of oxygen was not necessary.