An online coupon sent via email from Groupon is pictured on a laptop screen November 29, 2010 in Los Angeles. REUTERS/Fred Prouser Groupon is likely to pick Goldman Sachs and Morgan Stanley to lead a second-half initial public offering that could value the fast-growing daily deals site at $15 billion to $20 billion, according to a source.

Commodity trader Glencore’s planned $12 billion London listing has long been seen as the first step to merging with Xstrata, in what could be the biggest mining takeover in history. The question for most analysts and investors since the IPO was confirmed is not if the deal happens but when — and how.

BP’s partners in its Russian venture TNK-BP rejected the UK oil major’s offer to settle a dispute caused by its $18 billion tie-up with Rosneft, casting further doubt on the deal.

The New York Times reports that CVS Caremark is under pressure from consumer groups and shareholders to split up the merger of the drugstore chain and the pharmacy benefits manager.  Regulators are also investigating whether the company used anticompetitive behavior.