Sonochemical effects in the additions of furan to masked ortho-benzoquinones

The reactions of masked ortho-benzoquinones with furan under sonochemical irradiation were studied. Variation of the acoustic energy, temperature, and solvent composition permitted to optimize the yields, and provided insights into the mechanism. While the radical pathway could not be established, a double Michael stepwise pathway seems more probable, as shown by the effect of solvent polarity and the regioselectivity. The sonochemical effect involves most likely a mechanical micromixing, giving evidence to its role even in homogeneous systems. (C) 2002 Elsevier Science B.V. All rights reserved.