Synthesis and Properties of 4,4,9,9-Tetramethylparacyclophane-5,6,7,8-tetrone

Article abstract of DOI:10.1021/jo00027a045

The synthesis of 4,4,9,9-tetramethyl<12>paracyclophane-5,6,7,8-tetrone (26) has been achieved in a multistep procedure.Compound 26 is the first cyclic tetraketone whose structure has been studied by X-ray analysis.The key intermediates were 4,4,9,9-tetramethyl<12>paracyclophane-6,7-dione (22), 6,7-bis<(trimethylsilyl)oxy>-4,4,9,9-tetramethyl<12>paracyclophane-5,7-diene (24), and two epimeric 5,8-dihydroxy-4,4,9,9-tetramethyl<12>paracyclophane-6,7-diones 25a and 25b.X-ray analyses have been performed on 24, 25b and 26.That on 24 reveals a dihedral angle of 57 deg between the two silyenol ether groups.The product analyses and the configurations of 25a and 25b together with the isolation of the bis(epoxide) intermediate 28 allow conclusions to be drawn on the oxidation mechanism of 24 with m-CPBA (Rubottom reaction).The stability of 26 is ascribed to steric factors.