An Experimental and Computational Investigation of (α-Methylbenzylidene)carbene.
An Experimental and Computational Investigation of (α-Methylbenzylidene)carbene.
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(α-甲基亚苄基)卡宾的实验和计算研究。
DOI：
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发表时间：
2016
影响因子：
3.6
通讯作者：
D. Thamattoor
中科院分区：
文献类型：
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作者：
Xi Yang;Keith Languet;D. Thamattoor
在C6H6（或C6D6）中，1-（1-苯基乙基）-1a，9b-二氢- 1h -环丙[1]菲在室温下光解生成（α-甲基苄基）卡宾，该卡宾经过一个简单的Fritsch-Buttenberg-Wiechell （FBW）型重排生成1-苯基丙炔。炔完全由1,2-苯基移位产生，从（13）c标记前体的使用可以看出。该实验结果与CCSD(T)/cc-pVTZ//B3LYP/6-31+G*计算结果一致，计算结果表明，单重态碳的1,2-苯基位移只需克服3.8 kcal/mol的势垒，而1,2-甲基位移则需要克服11.9 kcal/mol的势垒。在环己烯进行光解反应时，主要产物是炔，但在光解产物中可以检测到碳烯环加合物，尽管收率较低。
Photolysis of 1-(1-phenylethylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, in C6H6 (or C6D6), at ambient temperature, produces (α-methylbenzylidene)carbene which undergoes a facile Fritsch-Buttenberg-Wiechell (FBW)-type rearrangement to 1-phenylpropyne. The alkyne results exclusively from a 1,2-phenyl shift as evident from the use of a (13)C-labeled precursor. This experimental result is consistent with CCSD(T)/cc-pVTZ//B3LYP/6-31+G* calculations which reveal that a 1,2-phenyl shift in the singlet carbene needs to overcome a barrier of only 3.8 kcal/mol whereas the 1,2-methyl shift has to surmount a much larger barrier of 11.9 kcal/mol. The alkyne remains the predominant product when the photolysis is carried out in cyclohexene but the carbene-alkene cycloadduct could be detected, albeit in low yield, in the photolysate.