THE DIELS-ALDER CYCLOADDITION, AN INTRIGUING PROBLEM IN ORGANIC SONOCHEMISTRY

Sonochemical Diets-Alder cycloadditions are discussed with the help of published examples and recent data from the authors' laboratories. Mo st of the significant results, in terms of rate and/or yield increases , are obtained when quinones are the dienophiles. A possible mechanism implies a redox process between the diene and dienophile, giving radi cal-ion intermediates. Convergent data lead to the conclusion that in other cases, where a concerted (or closely related) mechanism is proba ble, the sonochemical effect should remain modest, making necessary a re-evaluation of the physical effects of cavitation.