Preparations and properties of pseudo-geminal ketones of tris-[2.2.2]- and tetrakis[2.2.2.2]parazylylene

Pseudo-geminal bridged ketones of tris2.2.2]paraxylylene, 1, and of tetrakis2.2.2.2]paraxylylene, 2, were prepared and their spectral properties were investigated in comparison with those of dibenzosuberone, 3. The CO stretching band of 1 was observed at abnormally high frequency region (by ca. 50 cm^?1) compared with that of 3, while that of 2 was at a position similar to that of 3. The electronic spectrum of 1 showed that 1 has enormous loss of conjugation due to lack of coplanarity between CO and aromatics. The chemical shift of H⁰, ortho to CO, of 1 also supported this structural characteristic.