Ring opening of epoxides with catalytic amounts of Ce(IV) as ceric ammonium nitrate (CAN) are performed efficiently in the presence of water, Thiols and acetic acid under mild conditions. The epoxides are opened with high regio-and stereoselectivity and with good to excellent yields. The products formed from the reaction of polar substituted epoxides in acetic acid were found to be derivative of succinic acid diester. The mechanism of the reaction is believed to be a radical type, involving the formation of an epoxonium radical cation.