Modifying the Chemistry of the Phosphole Dienic System by α‑Vinylation

1-Phenyl-2-vinyl-3,4-dimethylphosphole
(4) was prepared from the corresponding 2-carboxaldehyde
via a Wittig reaction. The reaction of its P-W­(CO)5 complex 5 with [PhP-W­(CO)5] selectively takes place at
the vinyl double bond and gives the corresponding phosphirane 6 as a mixture of two diastereomers. The reaction of 4 with N-phenylmaleimide involves the phosphole
dienic system and gives the [4 + 2] 7-phosphanorbornene cycloadduct 7. The reaction of 5 with dimethyl acetylenedicarboxylate
either takes place at the phosphole dienic system and leads to the
vinyl phthalate 10 with loss of the phosphorus bridge
or involves the double bonds of the vinyl and one phosphole group
to give the [4 + 2] cycloadduct 9, which is oxidized
in situ to give 11 with two epoxides and one ketone functionality.
The products 6, 7, 9, and 11 were characterized by X-ray crystal structure analysis.