intermediacy of the 1:1 adduct 1 — the 2:1 adducts 2, with the major isomer 2a, the one with the anti-configuration as revealed by X-ray crystallography and rationalised by molecular mechanics. Diels-Alder reactions of the anti-bisdienophile 2a with 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane proceed with complete treble diastereoselectivity to give only one 1:1 adduct 3 and a single 2:1 adduct
由1,4,5,8-四甲基-
2,3,6,7-四溴萘生成的双
芳烃与
2,5-二甲基呋喃反应,通过1:1加合物1的中间体生成2:1加合物2,具有主要的异构体2a,一种具有反构型的异构体,如X射线晶体学所揭示并通过分子力学对其进行了合理化。所述的狄尔斯-阿尔德反应的抗-bisdienophile 2A与2,3,5,6- tetramethylidene -7-氧杂双环〔2.2.1〕
庚烷与完整高音非对映选择性进行,得到仅一个1:1个加合物3和一个单一2:1加合物4。