Organophosphorus compounds, Part 153; New phosphorus-carbon cage compoundsby Diels-Alder and homo Diels-Alder reactions of 1,3,5-triphosphabenzenes with alkynes

Eleven new phosphorus-carbon cage compounds 3a-d, 5a-e, 7, and 8 have been synthesized in mostly excellent yields by reactions of the 1,3,5-triphospha benzenes 1 with acetylene, several monosubstituted acetylenes, and cyclooct yne. While most of the alkynes react with the heterobenzenes 1 in a sequenc e of Diels-Alder and homo Diels-Alder reactions to furnish the cage-compoun ds 3a-d, 5a-e, and 7 with the same tetracyclic phosphorus-carbon skeleton, the reaction with tert-butylacetylene leads to the formation of the unexpec ted polycyclic compound 8 by way of an as yet unknown reaction mechanism. T he structure of the tetracyclic product 7 as well as that of the cage compo und 8 has been confirmed by X-ray crystallographic analyses.