Abstract
2-Cycloalkenylphenols 3 react under mild conditions with PCl3 to give the 10-chloro-2,3,4,10-tetrahydro-1H-9-oxa-10- phospha-phenanthrenes 4. The latter are readily hydrolyzed to afford the 1,2,3,4-tetrahydro-9-oxa-10-phospha-phenanthrene-10-oxides 5 in good to excellent yields.