Evidence of a spiro[2.5]octa-1,4,7-trien-6-one intermediate in the solvolysis of β-(p-oxidophenylene)vinyl bromides

Abstract

The exclusive formation of 3-(p-hydroxyphenyl)-2-phenylbenzofuran from the solvolysis of both 2-(p-acetoxyphenyl)-2-(o-methoxyphenyl)-1-and 2-(p-acetoxyphenyl)-1-(o-methoxyphenyl)-2-phenyl vinyl bromide and the formation of a 1:1 mixture of 3-(p-hydroxyphenyl)-2-(o-methoxyphenyl)- and 2-(o-ethoxyphenyl)-3-(p-hydroxyphenyl)-benzofuran from 2-(p-acetoxyphenyl)-2-(o-ethoxyphenyl)-1-(o-methoxyphenyl)vinyl bromide under alkaline conditions provide firm evidence for the presence of the title compound as the precursor of benzofurans of this type.