Ehrlich’s Reaction of Furanoeremophilanes

Abstract

Abstract 6-Ethoxyfuranoeremophilane and its synthetic analogue, 4-ethoxy-4,5,6,7-tetrahydrobenzofuran, reacted with p-dimethylaminobenzaldehyde (Ehrlich’s reagent) under acidic conditions in a 2:1 ratio to afford condensation products in 34% and 78% yields, respectively. 6-Hydroxyfuranoeremophilane and 4-hydroxy-4,5,6,7-tetrahydrobenzofuran afforded the same products as in the case of ethoxy derivatives, respectively. The intermediate 1:1 adduct was not obtained from 6-ethoxyfuranoeremophilane, but obtained from the synthetic analogue in low yield. It was deduced that the colored compound in Ehrlich’s test is the cationic species of the intermediate 1:1 adduct, and that the concentration of the colored intermediate in the reaction mixture is very low.