Dozens of major American companies are preparing to pull out of Iran as the Trump administration closes a narrow legal window that has allowed firms to operate there without violating U.S. sanctions.
The companies using the exemption include big conglomerates like Honeywell International Inc., Dover Corp. and General Electric Co. and insurers like Chubb Ltd., many of which sought to profit from growth in the Iranian energy industry. Some of the companies have already booked millions of dollars in revenue from their Iranian...