Best Products Inc., a chain of catalog showroom stores battered by leveraged buyout expenses and by changing consumer buying patterns, is seeking Chapter 11 federal bankruptcy protection after debt-restructuring efforts fell through.

Stewart Kasen, president and chief operating officer of the chain that posted $2.1 billion in sales last year, announced $30 million in immediate cost-cutting moves - including 350 layoffs and a pay freeze for those left.Kasen, citing the chain's extensive real estate holdings and $250 million cash on hand, predicted Best would emerge from Chapter 11 a stronger company. He said plunging holiday sales and vendors balking at shipping items without getting cash up front prompted the bankruptcy filing.

Sales figures for December have not been released. In an August filing with the Securities and Exchange Commission, Best reported $664.8 million in long-term debt, much stemming from a $1.14 billion 1988 buyout in which Best came under the control of Adler & Shaykin, a New York investment firm that used Manufacturers Hanover Trust Co. as the prime lender.

"The decision to file under Chapter 11 is always a difficult one," Kasen said. "We were forced to take this action as a result of the general economic decline, the tightening of both trade and bank credit and the substantial slowdown in consumer spending.

"We made every effort to restructure our debt outside of a formal court supervised process," he continued. "However, we and our major creditors concluded that the best way to protect the valuable long-term franchise of Best's business is to proceed with the protection of the court."

On Dec. 14, Kasen asked suppliers for patience and told them Dec. 21 they would get cash for items shipped after Dec. 19. But payments for earlier shipments were left in limbo.

In a Dec. 28 letter to vendors, Kasen said that the company was trying "to negotiate a financial recapitalization and financial restructuring" but that the "disappointing Christmas retail season and general economic forecasts have made discussions more difficult and tenuous. . . . We are less optimistic as to the ultimate success of the discussions."

Kasen said filing the bankruptcy petition "will remove the cloud of uncertainty that has been hanging over us and our vendor community for the past six months" and added he expects to soon complete arrangements for an additional $250 million of debtor-in-possession financing.

Best, one of the nation's largest catalog showroom retailers, operates 195 Best showrooms in 27 states. The company also operates Best Jewelry, a chain of 35 fine jewelry and giftware stores, and Tele-Mail, a nationwide mail-order service.

The layoffs involve employees at every level, including store and district office personnel, and represent about 2 percent of Best's 17,000 employees nationwide. Best laid off 120 workers a year ago this month, mostly at its headquarters, and 120 corporate personnel also were let go in January 1989.

Best was an innovator in the catalog showroom business, but that kind of retailing has lost market share to straight catalog outfits and high-volume discounters in recent years. The W. Bell catalog showroom company, based in Rockville, Md., filed for Chapter 11 protection last month.