Other buyouts are looking shaky. The television company Univision, which recently scrapped plans for a public offering, is shaking up its leadership. The parent company of the Winn-Dixie supermarket chain said this week it was seeking to restructure its debt, as it planned to close stores.

Not all troubled private equity deals end with a company winding down, as in the case of Toys “R” Us. Retailers like Gymboree and Payless ShoeSource have found second lives after emerging from bankruptcy, often with investments from new private equity or hedge fund owners willing to give the business another try.

But the deterioration of Toys “R” Us from a potential turnaround strategy to the end of an iconic brand — in a matter of months — shows just how difficult it can be for private equity to compete in a rapidly evolving industry. In retailing, Amazon is reordering everything on the store shelf. And children’s changing interest in games and toys, which now encompasses high-end electronics, adds to the complexity.

The company said on Thursday that it had no other option than to begin winding down about 730 stores around the United States. Toys “R” Us was still looking at the possibility of keeping 200 stores open and combining them with its Canadian operations. But no deal had been struck yet.

“This is a profoundly sad day for us,” the Toys “R” Us chief executive, David Brandon, said in a statement, “as well as for the millions of kids and families who we have served for the past 70 years.”

The toy business looked a lot simpler in 2005, when the private equity firms Bain Capital and Kohlberg Kravis Roberts and the real estate firm Vornado Realty Trust acquired the company for $6.6 billion.