RING TRANSFORMATION OF PHOSPHORUS-CONTAIN ING HETEROCYCLES .13. SYNTHESIS AND UTILIZATION OF 2-PHOSPHABICYCLO[2.2.2]OCTA-5,7-DIENE-DERIVATIVES

2-Phosphabicyclol[2,2.2]octa-5,7-diene 2-oxides have been prepared by the Diels-Alder cycloaddition reaction of dihydrophosphinine oxides an d dimethyl acetylenedicarboxylate. Starting from the mixture of the do uble bond-isomers of the dihydrophosphinines, the cycloadducts were al so obtained as isomeric mixtures. Several amide- and sulfide dirivativ es were also prepared by change in the functionality of the cycloadduc ts. The phosphabicyclooctadienes were characterized by P-31, C-13 and H-1 NMR, as well as mass spectral data. Thermal examinations showed th at the products had lost their bridging moiety above 200 degrees C. Pe rforming the thermolysis in the presence of hydroxy-compounds, the met hylene-phosphine-oxides formed could be trapped. Due to the milder cir cumstances required and the better yields of the phosphorylated produc ts, photolysis (254 nm) proved to be a much better method to achieve t he fragmentation. This method was also suitable for the generation of methylene-phosphine-sulfides. A suggestion is given for the mechanism of the fragmentation, and a side-reaction observed in the photolysis o f the P-alkoxy cycloadducts is briefly discussed. Deoxygenation of the P-methyl phosphabicyclooctadiene provided a phosphine losing its brid ging moiety under extremely mild circumstances. 2-Phosphapropene gener ated in this manner was catched in reaction with nucleophiles and isop rene.