Non-fluorinated vinyldiazo compounds with trans-configuration irrespective of the nature of 3-R1-substituent (R1 = H, Me, TBSO) even under ambient conditions easily cyclize to produce pyrazoles, while cis-stereoisomers undergo similar ring closure only at elevated temperatures or decompose to produce vinyloxocarbene reaction products. The 3-CF3-substituted analogues with cis- or trans-configuration do not produce pyrazoles at all, but on heating furnish only vinylcarbene derived products. DFT calculations of theoretical energy barriers adequately explain the different experimental reactivity found for stereoisomeric vinyldiazocarbonyl compounds, and a new model for their interconversion through the corresponding pyrazoles has been suggested.
反式结构的非
氟乙烯基重氮化合物,无论 3-R1 取代基(R1 = H、Me、TBSO)的性质如何,即使在环境条件下也很容易环化生成
吡唑,而顺式立体异构体只有在温度升高时才会发生类似的闭环,或者分解生成
乙烯基氧羰基反应产物。顺式或反式构型的 3-
CF3 取代类似物根本不会产生
吡唑,而是在加热时只产生
乙烯基羰基衍生产物。对理论能垒的 DFT 计算充分解释了立体异构体
乙烯基二氮羰基化合物的不同实验反应性,并提出了通过相应
吡唑实现相互转化的新模型。