VALENCEISOMERIC AZO BRIDGED CARBOCYCLES AND CYCLIC HYDRAZONES: INTRAMOLECULAR CYCLOADDITIONS AND CYCLOREVERSIONS THROUGH N-METHYLATION

Article abstract of DOI:10.1016/S0040-4020(01)85963-9

Unsaturated azo bridged carbocycles 1, 2, 5, 8, 12, 14 and 16 can easily be methylated with Me3OBF4 or MeI.Depending on structural and steric requirements and the anion, the quaternary salts obtained are stable 1-Me(1+), 2-Me(1+), 5a-Me(1+), 14a/b-Me(1+), 16a/b-Me(1+) with BF4(1-), undergo <4+2> cycloreversion (8a-Me(1+), 12-Me(1+) or intramolecular <3+2> cycloaddition after intermediate deprotonation, whereby the unusual hydrazine derivatives, the cage compounds 3-H(1+), 4-H(1+), 6-H(1+) and 11-H(1+) are formed.Systems wich contain the N=N and C=C function in 1,5-positions are isomeric with their <3,3> rearrangement products, the hydrazones endo-7, endo-10, endo-15 and endo-17.Methylation of the latter provokes the same consecutive reactions as for their azo isomers.These have been demonstrated to be the crucial intermediates for the formation of cage compound (e.g. endo-7b-Me(1+)-> 5b-Me(1+)->6-H(1+).Intermolecular methyl migration of quaternized azo compounds has been established, explaining the high yields of cage compounds which can be produced by the "b-series" only.