Priceline Group, the online travel booking service best known for its quirky ads featuring actor William Shatner, said Friday it has agreed to buy online restaurant-reservation service OpenTable.com for $2.6 billion in cash.

The boards of directors of both companies have approved the deal, which is expected to close in the third quarter subject to regulatory clearances, the companies said. At $103 per share, the purchase price represents a 46 percent premium over the closing price of OpenTable’s stock at the end of trading Thursday.