Benzodifurans. I. The synthesis of benzo[1,2‐b:5,4‐b]difuran and some methyl analogs

Abstract

AbstractThe first parent benzodifuran (XVI) and three di‐ and trimethylated derivatives have been synthesized and screened for erythemal activity (negative response). Two benzodifurans were prepared from resorcinol and 2‐methylresorcinol by acetylation, Fries rearrangement, alkylation of the resulting 4,6‐diacetylresorcinols with ethyl bromoacetate, saponification, and then cyclization of the (4,6‐diacetyl‐1,3‐phenylenedioxy)diacetic acids. Another was prepared from the Claisen rearrangement product of 1,3‐bis(allyloxy)‐2‐methylbenzene by acetylation, bromina‐tion, and cyclization. Ozonolysis of the Claisen rearrangement product gave additional support to the formulation of o‐hydroxyphenylaeetaldehydes as cyclic hemiacetals. The parent benzodifuran was synthesized from 5‐formyI‐6‐hydroxybenzofuran, which was prepared in two steps from 5‐bromo‐6‐methoxybenzofuran. Alkylation of the former with ethyl bromoacetate, saponification, and cyclization furnished benzo[1,2‐b.5,4‐b ]difuran. The ultraviolet and nuclear magnetic resonance spectra of the four benzodifurans are compared.