REDUCTION OF ORTHO-HYDROXYBENZALDEHYDES BY AQUEOUS TITANIUM TRICHLORIDE - A NEW ROUTE TO 2-(BENZOFURAN-2-YL)PHENOLS

Reduction of o-hydroxybenzaldehydes la-k by aqueous titanium trichloride is a new simple way to the synthesis of the title compounds 2a-k. The temperature at which the reduction occurs (50 or 80 °C) is related to the nature and position of the R group in the benzene ring. When the reduction is performed at 0 °C in the presence of acetaldehyde, stereoselective formation of 1,3-dioxolanes 7 occurs, due to in situ condensation with the intermediate diols. A mechanism is proposed to account for the formation of both 2 and 7. Two-dimensional NMR methods have been used to completely assign1H and 13C NMR resonances of the 2-(benzofuran-2-yl)phenols 2a-d,f-h. © 1990, American Chemical Society. All rights reserved.