Traders on the floor of the New York Stock Exchange.

Burger King Worldwide –Burger King is in discussions with Canadian doughnut chain Tim Hortons about a possible merger. Such a deal would be structured as a tax inversion, with the combined company headquartered in Canada .

Ann Inc –Activist investors Engine Capital and Red Alder have delivered a letter to the board of the Ann Taylor parent, saying the company is deeply undervalued and urging Ann Inc. to explore all available strategic alternatives to enhance shareholder value.

BlackBerry —The smartphone maker won another court victory against Typo Products, which markets a BlackBerry-like keyboard that fits on an iPhone. A U.S. court upheld a preliminary injunction that prohibited the sale of that product.

Check out which companies are making headlines before the bell:

U.S. Steel — The steel maker's stock was upgraded to "outperform" from "underperform" at Credit Suisse, with the firm citing U.S. Steel's cost advantage over competitors for its raw materials.

PulteGroup—The home builder is buying the real estate assets of Dominion Homes for an undisclosed amount. Dominion operates in various markets in Kentucky and Ohio.

InterMune—Switzerland's Roche agreed to buy the U.S. based biotech firm for $8.3 billion in cash. The deal is worth $74 per share, 38 percent above Friday's closing price.

Goldman Sachs—Goldman announced a $1.2 billion settlement with the Federal Housing Finance Agency over mortgage-backed securities bought by Fannie Mae and Freddie Mac between 2005 and 2007. Reports of the settlement had been circulated during the trading day on Friday.

Allergan–Investor Bill Ackman said investors owning 31 percent of the Allergan's shares have asked for a special meeting. Ackman's Pershing Square and Valeant Pharmaceuticals have a $52 billion hostile bid on the table for Allergan, which has so far been rebuffed.

Sony–The company's PlayStation Network is back online after a cyber attack shut it down over the weekend. Sony said no personal information was compromised during the attack, which was accompanied by a bomb threat on a flight carrying a top Sony executive.

—By CNBC's Peter Schacknow

Questions? Comments? Email us at marketinsider@cnbc.com