A top Wall Street lawyer, he worked on some of the biggest corporate mergers in history, including KKR’s takeover of Nabisco in 1989. He also served in the Carter administration and in city government.

Richard Beattie, a mergers lawyer who helped pioneer private equity takeovers — work that was immortalized in the much-lauded book “Barbarians at the Gate” — and who served in Washington and New York City government, died on Friday at his home in Manhattan. He was 86.

His daughter Lisa Beattie Frelinghuysen said the cause was cancer.

Over nearly six decades at the white-shoe New York firm Simpson Thacher & Bartlett, the soft-spoken Mr. Beattie — Dick, as he was widely known — became one of Wall Street’s most-sought corporate advisers.

He helped put together AOL’s $165 billion takeover of Time Warner in 2001 and JPMorgan Chase’s $58 billion acquisition of Bank One in 2004, and advised the board of the