Death of Subway’s nuclear physicist founder throws sandwich chain’s future into doubt

The death of a nuclear physicist who co-founded Subway Restaurants has thrown the fast-food giant’s future into doubt, with dealmakers fretting that hopes to sell the struggling chain look more complicated than ever.

Peter Buck — whose $1,000 loan to Fred DeLuca in 1965 to start a sandwich shop in Bridgeport, Conn. launched a global fast-food empire that made him a billionaire — died last week at the age of 90, the company said.

What’s less known is the fact that Subway earlier this year held informal talks to possibly sell itself to Restaurant Brands International, the Brazil-based owner of Burger King, sources close to the situation said. Those talks fizzled, the sources said, culminating in Restaurant Brands’ move last week to instead buy Subway’s smaller sandwich competitor Firehouse Subs for $1.1 billion…