Morton Pierce, a Dewey vice chairman, said he will be joining White & Case. He will be joined by seven other corporate and M&A partners in New York, said White & Case spokeswoman Oonagh Bates.
Representatives for Dewey & LeBoeuf did not respond to requests for comment.
Pierce's departure is yet another blow for Dewey, which has been struggling against a flood of partner defections this year. Pierce, who had been chairman of predecessor firm Dewey Ballantine, has handled several multibillion dollar deals, including Walt Disney Co's $4 billion acquisition of Marvel Entertainment in 2009 and its $7.4 billion acquisition of Pixar in 2006.
Dewey was until recently among the top 20 largest law firms in the United States, with 1,040 lawyers, according to an annual survey by the National Law Journal, an industry publication.
But since January, it has lost nearly 100 of its 300 partners as it struggles with mounting debt. It is considering a number of alternatives including deals with other law firms.
Merger talks with SNR Denton, the latest merger candidate, have come to an end, a person briefed on the matter said. The talks fell apart after Dewey said that its former chairman, Steven Davis, was under investigation by the Manhattan district attorney's office, according to the person, who spoke on condition of anonymity. Davis has denied wrongdoing.
Dewey had previously been in talks with Greenberg Traurig about a possible transaction, but those talks also ended, Dewey said Sunday.
Martin Bienenstock, a bankruptcy partner at Dewey and a member of the firm's four-person office of the chairman, said in an email Thursday morning that talks "are not off with any firm, they simply change scope."
Dewey, which had offices in 26 cities around the world, was the product of a 2007 merger between New York-based firms Dewey Ballantine and LeBoeuf, Lamb, Greene & MacRae.
Pierce's departure was the latest, and one of the highest-profile, in a flood of defections.
Morgan, Lewis & Bockius said on Thursday it had hired three litigation partners from Dewey & LeBoeuf's London office, including its managing partner, Peter Sharp.
And, while SNR Denton said it is not talking about a merger, it appears to be considering hiring lawyers from Dewey. SNR Denton Chairman Elliott Portnoy sent an email Wednesday to SNR Denton partners saying the firm was making efforts to attract the "strong, profitable parts" of Dewey, according to an SNR Denton partner who read the email.
Portnoy declined to comment. Jeff Scalzi, a spokesman for SNR Denton, said "we are looking at selective acquisitions, but we aren't commenting further."
Another firm, Patton Boggs, has been exploring opportunities short of a full merger, a different source familiar with the matter said on Monday.
In an email Monday, Dewey management "encouraged" partners to seek out other jobs.
Bienenstock said Monday that bankruptcy was "not in current plans."
"If real property and equipment leases are assumed by other firms or renegotiated, and the lenders realize on their accounts receivable and inventory, there may be no need for judicial intervention," Bienenstock said.
On Monday, Dewey obtained a two-week extension in negotiations between it and a bank group over a $100 million credit line. Dewey has drawn down $75 million on that credit line.
(Editing by Phil Berlowitz and M.D. Golan)
By Nate Raymond and Leigh Jones