WILMINGTON, Del. (July 24)—DuPont Co. has agreed to buy ChemFirst Inc. in a cash transaction valued at $408 million. The global supplier of electronic chemicals and materials to the semiconductor market and specialty intermediates for polyurethane and other applications posted sales of $278 million in 2001. ChemFirst's electronic materials business segments will become part of DuPont Electronic Technologies, and the chemical intermediates unit will join DuPont Chemical Solutions Enterprise. The acquisition will expand DuPont's semiconductor business while the intermediates division will improve sales, the firm said. The agreement is subject to approval from ChemFirst shareholders and regulatory agencies.