Laticyclic Conjugated Polyenes. Study on Diels-Alder Cycloadditions of a Facially Dissymmetric Maleic Anhydride.
The tetracyclic ring-fused, facially dissymmetric maleic anhydride 2 was synthesized from compound 9 obtained from the Diels-Alder cycloaddition of the bicyclic ring-fused cyclohexadiene 1 and acetylenedicarboxylate. Maleic anhydride 2 readily underwent the Diels-Alder cycloadditions with anthracene, 1,3-diphenylisobenzofuran, cyclopentadiene, 1,3-cyclohexadiene, 6,6-dimethylfulvene, and o-quinodimethane. All the cycloadditions occurred exclusively on the pi-face syn to the etheno bridge of 2, thereby in cases of the cycloadditions with anthracene, cyclopentadiene, 1,3-cyclohexadiene, and 6,6-dimethylfulvene producing the corresponding adducts 11a, 18b, 22b, and 23b that contain three double bonds aligned in parallel. The structures of 18b and 22b were unequivocally established by the X-ray structural determinations. The molecular structure of maleic anhydride 2 was analyzed by X-ray crystallography to have a pyramidalized dienophilic double bond, which appeared to correlate well with the observed pi-facial selectivity.
Chou
Teh-Chang
TC
Department of Chemistry, National Chung Cheng University, Ming Hsiung, Chia Yi 621, Taiwan, Department of Chemistry, Tung Hai University, Taichung 400, Taiwan, and Institute of Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan.
Jiang
Tzong-Shing
TS
Hwang
Jenn-Tsang
JT
Lin
Kuan-Jiuh
KJ
Lin
Cheng-Tung
CT