Thermal isomerizations of cis,anti,cis-tricyclo[6.4.0.02,7]dodec-3-ene to trans- and cis,endo-tricyclo[6.2.2.02,7]dodec-9-ene: diradical conformations and stereochemical outcomes in [1,3] carbon shifts
作者:Phyllis A. Leber、Andrew R. Bogdan、David C. Powers、John E. Baldwin
DOI:10.1016/j.tet.2007.02.088
日期:2007.7
gas-phase thermal isomerizations at 315 °C of cis,anti,cis-tricyclo[6.4.0.02,7]dodec-3-ene to trans-tricyclo[6.2.2.02,7]dodec-9-ene and to cis,endo-tricyclo[6.2.2.02,7]dodec-9-ene favor the former, the more geometrically strained product, by a ratio of 2.4:1. These products correspond to suprafacial inversion (si) and suprafacial retention (sr) stereochemical outcomes. The reaction stereochemistry shown by
在315℃下的气相热异构化顺式,反,顺-三环[6.4.0.0 2,7 ]十二碳-3-烯,以反式-三环[6.2.2.0 2,7 ]十二碳-9-烯,并顺式,内-三环[6.2.2.0 2,7 ] dodec-9-ene有利于前者,其在几何上更易变形,比例为2.4:1。这些产物对应于表面上反转(si)和表面上保留(sr)的立体化学结果。反应的立体化学由11个碳的同系物顺式,反式,顺式-三环[6.3.0.0 2,7] undec-3-ene截然不同:发生[1,3]碳转移,仅得到“禁止”的sr产物。两个相关的双环乙烯基环丁烷,8-氘-和8-外甲基双环[4.2.0] oct-2-enes证明在[1,3]位移中反应立体化学偏向相反,但是在12-碳三环系统和8-碳中相同的si:sr比率的exo-甲基双环类似物异构化!这些发现促使人们重新思考结构影响对所涉及的烷基,烯丙基二自由基反应性中间体可用的构象偏好的影响。