oxygen in further solvent(s) under vac./Ar: 298 K, oxidative degradation by purified and dried oxygen (pressure 40-101.33 kPa) in manometric assembly, solvent: phenylacetylene or p-xylene; not isolated, detected by elem. anal., GC, IR, and UV;

in benzene byproducts: CO2; under vac./Ar: room temp., with and without addn. of cyclopentadiene; not isolated, detected by elem. anal., GC, IR, and UV;

in tetrahydrofuran N2 atmosphere, treatment of THF solns. (2 equiv. H2CPMe3, -78°C), stirring (5 h, warming to 0°C), voltiles removal (0°C); extraction (benzene), filtn. (Celite), recrystn. (toluene); elem. anal.;

in tetrahydrofuran even at 100°C slow reaction;;