Regiochemistry of the reaction of 3,4,6-triisopropyl-1,2-benzoquinone with phenylacetylene in the presence of phosphorus trichloride

The reaction of 3,4,6-triisopropyl-1,2-benzoquinone with phenylacetylene and phosphorus trichloride gave 2,6-dichloro-5,7,8-triisopropyl-4-phenyl-1,2λ5-benzoxaphosphinine 2-oxide whose structure was determined by X-ray analysis.