Major corporate reorganizations may lie ahead for at least three big companies this week.

On Tuesday, Phillips Petroleum Co. has scheduled a meeting with its employes to discuss its restructuring plans. The meeting comes amid speculation that Phillips is a prime takeover candidate for 1988.

On Wednesday, A.H. Robins Co. is scheduled to file its reorganization plan with the U.S. Bankruptcy Court in Richmond that will detail how the company plans to emerge from its voluntary decision to seek protection from its creditors. The key to the plan will be Robins' selection of a merger partner. Despite the multimillion-dollar claims filed against Robins by women who say they were injured by the company's Dalkon Shield intrauterine birth-control device, Robins is being courted by three pharmaceutical giants: Rorer Group Inc., American Home Products Corp. and the French firm Sanofi.

On Thursday, Pillsbury Co.'s board is scheduled to meet amid reports that the company is about to undergo a major shakeup. Pillsbury has confirmed that major changes are in store but denied rumors that it was about to sell its Burger King chain or other restaurant operations.

Meanwhile, the nation's retailers will finally disclose how good or bad their Christmas season was on Thursday when they release their December sales figures. The figures will be watched closely by economists to determine the health of the economy.

Also this week, a delegation of trade officials from South Korea is expected to come to Washington to present a compromise trade package to correct a growing trade imbalance and head off any U.S. retaliation. And on Friday, the presidential commission appointed to investigate the causes of the stock market collapse, and to make recommendations for changes, plans to submit its report to President Reagan.