The Reaction of Diazo Ketones in the Presence of Metal Chelates. VIII. The Stereochemistry of the 1,3-Dipolar Cycloaddition of 1-Methoxy- 2-benzopyrylium-4-olates to Ethylenic Dipolarophiles
作者:Toshikazu Ibata、Kimiko Jitsuhiro、Yoshie Tsubokura
DOI:10.1246/bcsj.54.240
日期:1981.1
according to the experimental results obtained using 3-deuterated 3a. The stereospecificity of the cycloaddition was confirmed in the reactions of dimethyl fumarate, dimethyl maleate, and trans-1,2-dibenzoylethylene; this stereospecificity was explained by the concerted (π2S+π4S) mechanism. The exo/endo ratios of the adducts of N-substituted maleimides may be explained by the combination of the steric
1,3-偶极环加合物是在 1-甲氧基-2-苯并pyrylium-4-olate (3a) 与烯属偶极亲和物如富马酸二甲酯、马来酸二甲酯、马来酸酐、反式 1,2-二苯甲酰乙烯、N 的反应中获得的-取代的马来酰亚胺和苊。加合物的构型是基于加合物的次甲基质子的 NMR 耦合模式结合氘实验确定的。先前报道的 3a 与富马酸二甲酯的加合物结构根据使用 3-氘代 3a 获得的实验结果进行校正。在富马酸二甲酯、马来酸二甲酯和反式-1,2-二苯甲酰乙烯的反应中证实了环加成的立体定向性;这种立体特异性可以通过协调的 (π2S+π4S) 机制来解释。