Reactions of [1.1.1]propellane

Article abstract of DOI:10.1021/ja00162a022

The free radical addition reactions of [1.1.1]propellane (1) are described in some detail and allowed the preparation of a wide variety of 1,3-disubstituted bicyclo[1.1.1]pentanes. The reaction of 1 with free radicals was more rapid than that of bicyclo[1.1.0]butane (2), whereas bicyclo[2.1.0]pentane (3) was relatively inert. In some cases the free-radical additions led to oligomers, and in the case of tetrahydrofuran addition the chain-transfer constant was measured. The addition of thiophenol to 1 followed by reduction with the lithium radical anion from 4,4′-di-tert-butylbiphenyl gave 1-lithiobicyclo[1.1.1]petane, from which a variety of 1-substituted bicyclo[1.1.1]pentanes may be prepared. In the Baeyer-Villiger oxidation of 1-benzoylbicyclo[1.1.1]pentane, the terf-butyl group migrated in preference to the bicyclopentyl group. Conversion of the ketone to the tosylhydrazone followed by base treatment gave products of the type expected from the corresponding carbene. The reaction of 1 with NO in carbon disulfide gave a unique reaction in which nitro and thiocyano groups were introduced. The reactions of 1, 2, and 3 with NO₂ also were examined. Whereas 1 gave 1,3-dinitrobicyclo[1.1.1]pentane, the other hydrocarbons followed different reaction paths. The reaction of 1 with electron-deficient alkenes and alkynes are described in some detail and are compared with the corresponding reactions of 2 and 3. Here, the relative reactivities of 1 and 2 were often comparable but varied considerably with the reagent used. Again, 3 was relatively unreactive. The reaction of 1 with Rh(I) gave a dimer, and evidence is presented for a metallocarbene intermediate.