New Phosphorus−Carbon Cage Compounds by Diels−Alder and Homo Diels−Alder Reactions of 1,3,5-Triphosphabenzenes with Alkenes

Abstract

Ethylene, various monosubstituted alkenes (acrylic acid derivatives, styrene), as well as some selected disubstituted alkenes (maleic acid derivatives, fumaric acid derivatives, norbornene, cyclopentadiene) undergo Diels−Alder reactions with the 1,3,5-triphosphabenzenes 1 under mild conditions to furnish the dihydrotriphosphabarrelenes 9, 11a−c, 13a−e, 15a−d, 17a,b, and 24. The monoadduct 26 as well as the diadducts 27 and 28 are isolated following the reaction with norbornadiene. Cyclopropene is the only alkene to undergo a Diels−Alder/homo Diels−Alder reaction sequence to afford the hexacyclic system 20.