Groupon surged in premarket trading after a report that the discount-slinging website is actively seeking a buyer. The merchandise and voucher vendor has approached several public companies in recent weeks to try to drum up interest in a sale, Recode reported on Saturday, citing two people it said were briefed on the effort and without identifying the companies involved. Chicago-based Groupon’s shares rose as much as 12 percent before the start of regular trading in the U.S.