SAN FRANCISCO — The San Francisco Chronicle joined the lengthening list of imperiled newspapers Tuesday as its owner set out to purge the payroll and slash other expenses in a last-ditch effort to reverse years of heavy losses. If it can’t reduce expenses dramatically within the next few weeks, the Hearst Corp. said it will close or sell the Chronicle, northern California’s largest newspaper with a paid weekday circulation of 339,430. Hearst didn’t specify a savings target nor a deadline for wringing out the expenses. A Hearst spokesman didn’t immediately respond to messages Tuesday. But management made it clear that the cost-cutting will require a significant number of layoffs. ‘Our current situation dictates that we accomplish these cost savings quickly,’ Chronicle Publisher Frank Vega wrote in a memo to the staff. ‘Business as usual is no longer an option.’ The Chronicle has given Hearst financial headaches since the New York-based company bought the newspaper in a complex deal valued at $660 million. The late 2000 acquisition proved to be ill-timed. Shortly after Hearst took control, the San Francisco Chronicle was hard hit by a high-tech bust that caused its advertising revenue to shrivel. […]