3,5-Diphenyl-2-phosphafuran: Synthesis, Structure, and Thermally Reversible [4 + 2] Cycloaddition Chemistry

Treatment
of trans-chalcone with dibenzo-7-phospha­norborna­diene
EtOPA (A = C14H10,
anthracene), a source of ethoxy­phosphinidene, followed by formal
elimination of ethanol yields 3,5-diphenyl-2-phosphafuran (DPF) in
43% yield. We show that the phosphadiene moiety of DPF is a potent
diene in the Diels–Alder reaction and reacts with dienophiles
dimethyl acetylenedicarboxylate (DPF·DMAD, 68%), norbornene (DPF·norbornene,
73%), and ethylene (DPF·C2H4, 80%) under
ambient conditions. Mild heating of DPF·C2H4 results in the corresponding retro-Diels–Alder reaction,
establishing DPF as a molecule that is able to reversibly bind ethylene.