The pericyclic reactions of 2,5-bis(methoxycarbonyl)-3,4-diphenylcyclopentadienone (1a) with both
allylic and propargylic amines have been investigated. The reaction proceeded via initial formation
of the 1,4 adducts followed by the ene cyclization and/or sequential pericyclic reactions depending
upon the structures of the amines. The reaction of 1a with diallylamine (2a) gave the tetracyclic
compound (3a). On the other hand, the reaction of 1a with 2-propynylamine (2c) gave exclusively
the bicyclic compound (5c). In the reactions with the secondary 2-propynylamines (2d,e), the
tetracyclic compounds (3d,e) were exclusively formed. The reactions of 1a with α-branched primary
1,1-dialkyl-2-propynylamines (2f,g) gave mixtures of 3- and 5-type compounds. The tetracyclic
compounds 3 were formed from the intramolecular [4+2]π cycloadditions of the [1,5]-sigmatropic
rearrangement products of the 1,4 adducts of 1a and 2, followed by the [1,5]-sigmatropic
rearrangement of hydrogen and dehydrogenation. The bicyclic compounds 5 were derived from the
[2π+2π+2σ] reaction of the 1,4 adducts of 1a and 2. The one-pot multistage sequential pericyclic
reactions were discussed on the basis of the X-ray crystallographic structures and the MO calculation
data.