Thermal Decomposition of Substituted Norbornadienone Ketals
Thermal Decomposition of Substituted Norbornadienone Ketals
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取代降冰片二烯酮缩酮的热分解
DOI：
10.1021/ja00955a035
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发表时间：
1966
影响因子：
15
通讯作者：
S. D. Mcgregor
中科院分区：
文献类型：
--
作者：
D. Lemal;E. Gosselink;S. D. Mcgregor
四氯降冰片二烯酮缩酮与炔属亲二烯体发生Diels-Alder反应，生成1，2，3，4-四氯降冰片二烯酮缩酮，其中部分在原位分解，部分以纯品形式存在。这些化合物在热解时得到两种芳香族产物：失去缩酮桥的产物和以酯官能团形式保留缩酮桥的产物。离子和自由基的芳构化途径已被假定;溶剂极性和取代基的选择betweenthese机制的影响进行了讨论。有证据表明，缩酮桥失去了形式的二氧卡宾，虽然乙撑二氧卡宾mayhave碎片，因为它是产生的。二甲氧基卡宾衍生的产物高度依赖于反应条件。而在浓溶液中形成的二聚体tetramethoxylene产率很好，原甲酸三甲酯是一个主要的产品在稀溶液和乙酸甲酯，二氧化碳，和甲基自由基产生在vaporphase.The本study 1进行的目标是生成二氧卡宾，并阐明其化学。这些物种之所以引起人们极大的兴趣，阿利亚是因为它们的化学性质难以预测。由于氧的给电子能力，二氧卡宾被期望显示出介于亲电的二卤代和单氧卡宾3与显著亲核的氨基卡宾4之间的性质;然而，中间地带显然涵盖了广泛的反应性。事实上，没有先验的基础来排除二氧卡宾优先于经历杂原子取代的卡宾的熟悉反应而重排或断裂的可能性。
The Diels-Alder reaction of tetrachlorocyclopentadienone ketals with acetylenic dienophiles yielded 1, 2, 3, 4-tetrachloronorbornadienone ketals, some of which decomposed in situ and some were obtained in pure form. When pyrolyzed, these compounds gave twokinds of aromatic products: those which had lost the ketal bridge and those which had retained itin the form of an ester function. Both ionic and radical pathways for aromatization have been postulated; the influence of solvent polarity and of substituents on the choice betweenthese mechanisms is discussed. Evidence is presented that the ketal bridge was lost in the form of a dioxycarbene, though ethylenedioxycarbene mayhave fragmented as it was generated. The products derived from dimethoxy-carbene were highly dependent upon the reaction conditions. Whereas the dimer tetramethoxyethylene was formed in good yield in concentrated solution, trimethyl orthoformate was a major product in dilute solution and methyl acetate, carbon dioxide, and methyl radicals were generated in the vapor phase.The present study1 was undertaken with the goal of generating dioxycarbenes and elucidating their chemistry. These species were of considerable interest for the reason inter alia that their chemistry was difficult to predict. By virtue of the electron-donating capacity of oxygen, dioxycarbenes were expected to display properties intermediate between the electrophilic dihalo-and monoxycarbenes3 on the one hand and the markedly nucleophilic aminocarbenes4 on the other; the middle ground, however, obviously covers a broad range of reactivity. Indeed, there was no a priori basis for excluding the possibility that dioxycarbenes would rearrange or fragment in preference to undergoing familiar reactions of heteroatom-substituted carbenes.