Tetra-acetylethylene : a new intermediate for synthesising heterocyclic rings
作者:G. Adembri、F. De Sio、R. Nesi、M. Scotton
DOI:10.1039/j39700001536
日期:——
Tetra-acetylethylene (I), prepared by oxidation with iodine of the dithallium(I) salt of tetra-acetylethane (II), reacts with hydrazine to give a mixture of 1,4,5,8-tetramethylpyridazino[4,5-d]pyridazine (IV) and 6-amino-1,4,5,7-tetramethylpyrrolo[3,4-d]pyridazine (V). Treatment of compound (I) with hydrochloric or hydrobromic acid yields furan derivatives, whose structures can be established by chemical
四acetylethylene(我),通过氧化用碘四acetylethane(II)的dithallium(I)盐的制备,与肼反应,得到1,4,5,8- tetramethylpyridazino [4,5的混合物d ]哒嗪(IV)和6-氨基-1,4,5,7-四甲基吡咯并[3,4- d ]哒嗪(V)。用盐酸或氢溴酸处理化合物(I)得到呋喃衍生物,其结构可以通过化学和光谱方法确定。化合物(I)与2,3-二甲基丁二烯形成Diels-Alder加合物。
Synthesis, x-ray structural analysis and photochemistry of novel syn-periplanar bis-azo-skeletons
Skeletons with syn-periplanar bis-azo-chromophoric units (8,18,19) have been synthesized (8: transannular NN/NN-distances 2.939(2.999) Å, interorbital angle ω = 154.3°, X-ray analysts). In no case azo/azo-photocycloaddition has been observed upon direct or sensitized excitation.
rigid, “parallel-in-plane” preorientedbis(diazenes), with N=N/N=N distances (d) of 3.3−2.9 A and interorbital angles (ψ) of 142−164° (X-ray crystal structures). DFT calculations (B3LYP/6−31G*) and one-/two-electron reduction experiments with the two least preoriented, most “distant” bis(diazenes) (dN=N/N=N ca. 3.3 A; ψ 142−146°) provide more insight into the structural prerequisites for bis(homoconjugative)
interpreted by invoking the zwitterion 26 as common intermediate. Monoolefines that cannot generate stable carbenium ions don't give [4+2]cycloadducts with 7a. In contrast, α-methylstyrene yields the oxa Diels–Alder product 30. The structures of (E)-7b, 19, 25, and 27 are established by X-ray diffraction analyses.