The inherently strained furan-fused
cyclobutenes, in situ generated via cycloisomerizations
of allenyl ketones bearing cyclopropyl
moiety under gold catalysis, have been utilized as reactive building
blocks toward cross cycloadditions. The [4 + 2] and [3 + 2] annulations
of these species with benzo[c]isoxazoles and N-iminoquinazolinium ylides furnish various three-dimensional
cyclobutane-bridged polyheterocycles in good yields. A wide range
of typically electron-deficient 1,3-dienes, heterodienes, and 1,3-dipoles
can trap furan-fused cyclobutenes to afford several polycyclic architectures.