Novel fulvenes capto-dativelly substituted at $C_6$

A set of four fulvenes bearing both electron-withdrawing and -donating aryl groups at $C_6$ was prepared and shown to be fairly stable, except for the dimerisation of the anisyl-nitrophenyl-fulvene 1a, which also underwent a (4\pi + 2\pi) cycloaddition with C,N-diphenylnitrone.