Syntheses of systems containing strained double bonds: cycloaddition reactions of trans-3,8-dicarbomethoxydihydroheptalene
摘要:
The two strained systems 5 and 6 are the objectives of synthetic and structural studies because of their relationship to syn- and anti-sesquinorbornenes. The Diels-Alder cycloaddition of maleic anhydride, p-benzoquinone, dimethylacetylene dicarboxylate, singlet oxygen, and benzyne to trans-3,8-dicarboxydihyroheptalene 7 have been investigated. It is shown that the second addition to this system goes only with dienophiles such as singlet oxygen and benzyne. Compound 15, a derivative of the anti compound 6, was synthesized and the structure investigated by X-ray diffraction. Although the molecule is strained, the central double bond exhibits a planar environment. The structure of compound 9, a precursor to a derivative of the syn compound 5, is reported. The double-bond environment at the ring juncture differs significantly from planarity, and the folding angle is 7.3-degrees.