Qin Changyong, Davis Steven R
Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA.
J Org Chem. 2003 Nov 14;68(23):9081-7. doi: 10.1021/jo035168s.
The thermal isomerization of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene was studied using ab initio methods at the multiconfiguration self-consistent field level. The lowest-energy pathway for thermolysis of both structures proceeds through the (E,Z)-1,3-cycloheptadiene intermediate. Ten transition states were located, which connect these three structures to the final product, (Z,Z)-1,3-cycloheptadiene. Three reaction channels were investigated, which included the conrotatory and disrotatory ring opening of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene and trans double bond rotation of (E,Z)-1,3-cycloheptadiene. The activation barrier for the conrotatory ring opening of tricyclo[4.1.0.0(2,7)]heptane to (E,Z)-1,3-cycloheptadiene was found to be 40 kcal mol(-1), while the disrotatory pathway to (Z,Z)-1,3-cyclohetpadiene was calculated to be 55 kcal mol(-1). The thermolysis of bicyclo[3.2.0]hept-6-ene via a conrotatory pathway to (E,Z)-1,3-cycloheptadiene had a 35 kcal mol(-1) barrier, while the disrotatory pathway to (Z,Z)-1,3-cyclohetpadiene had a barrier of 48 kcal mol(-1). The barrier for the isomerization of (E,Z)-1,3-cycloheptadiene to bicyclo[3.2.0]hept-6-ene was found to be 12 kcal mol(-1), while that directly to (Z,Z)-1,3-cycloheptadiene was 20 kcal mol(-1).
使用多组态自洽场水平的从头算方法研究了三环[4.1.0.0(2,7)]庚烷和双环[3.2.0]庚-6-烯的热异构化反应。两种结构热解的最低能量途径均通过(E,Z)-1,3-环庚二烯中间体。确定了十个过渡态，它们将这三种结构与最终产物(Z,Z)-1,3-环庚二烯相连。研究了三个反应通道，包括三环[4.1.0.0(2,7)]庚烷和双环[3.2.0]庚-6-烯的顺旋和对旋开环以及(E,Z)-1,3-环庚二烯的反式双键旋转。发现三环[4.1.0.0(2,7)]庚烷顺旋开环生成(E,Z)-1,3-环庚二烯的活化能垒为40 kcal mol(-1)，而生成(Z,Z)-1,3-环庚二烯的对旋途径计算值为55 kcal mol(-1)。双环[3.2.0]庚-6-烯通过顺旋途径生成(E,Z)-1,3-环庚二烯的热解能垒为35 kcal mol(-1)，而生成(Z,Z)-1,3-环庚二烯的对旋途径能垒为48 kcal mol(-1)。发现(E,Z)-1,3-环庚二烯异构化为双环[3.2.0]庚-6-烯的能垒为12 kcal mol(-1)，而直接异构化为(Z,Z)-1,3-环庚二烯的能垒为20 kcal mol(-1)。
