The (3-amino-1-ethoxyalkenylidene)pentacarbonylchromium complexes 1 and 8 react with bulkily substituted terminal alkynes 2 and 9 in tetrahydrofuran to give η5-tricarbonyl(dihydroazepinyl)chromium complexes 3 and 12a which can be isolated in low yields. When the reactions are carried out in pyridine, the formal [5 + 2] cycloaddition is favored, but the complexes of type 12 are immediately further transformed to 2-(isobutyrylmethylene)pyrrolidines 13 in good yields.
(3-
氨基-1-乙氧基亚烯基)五羰基
铬络合物 1 和 8 与大量取代的末端炔 2 和 9 在
四氢呋喃中发生反应,生成δ-5-三羰基(二氢氮杂环庚基)
铬络合物 3 和 12a,这些络合物可以低产率分离出来。当反应在
吡啶中进行时,形式上的[5 + 2]环化反应更有利,但 12 型络合物会立即进一步转化为 2-(异丁酰亚甲基)
吡咯烷 13,产率很高。