Groupon.com

Groupon (GRPN - Get Report) , under pressure from activist investors to boost its value, is pursuing an acquisition and the target could be Yelp (YELP - Get Report) , people familiar with the matter told The Wall Street Journal.

"It is reasonable to conclude that a relatively large acquisition by Groupon is forthcoming," Robert Chapman, founder of California investment firm Chapman Capital LLC, told the Journal. Chapman had been building a stake in Groupon, the daily deals site, in recent weeks.

Groupon and Yelp would be a logical tie-up and a combination would create a company with earnings before interest, taxes, depreciation and amortization of $900 million to $1 billion, the people told the Journal.

A takeover or merger could create synergies saving at least $200 million, the people said.

Chapman - who held 10 million shares, or 1.5% of Groupon's stock - told the Journal he sold part of his stake Tuesday because he thinks a large acquisition would be too risky for Groupon.

He had been lobbying the company to buy back more of its own stock and tried to create an alliance with other shareholders to exert pressure on Groupon's management.

Chapman, in a letter to Groupon CEO Rich Williams, also called for a sale of Groupon. 

Groupon shares fell 3.16% in trading Thursday to $2.92.

Yelp, the online-review company, rose 2.37% to $35.42.