Styrene carbonate is synthesized by a direct benign route in the presence of tetrabutylammonium bromide (TBAB) from styrene, compressed CO2 and tert-butyl hydroperoxide (TBHP) as oxidant, in which two sequential reactions of epoxidation and cycloaddition are coupled for a one-pot synthesis. Various reaction parameters, such as CO2 pressure, reaction temperature and time, TBAB concentration, molar ratio of TBHP to styrene and oxidant types, were investigated. CO2 pressure was found to play a crucial role in achieving the high yield of styrene carbonate. A plausible reaction mechanism was also proposed. (C) 2004 Elsevier B.V. All rights reserved.