Department of Chemistry, Franklin & Marshall College, Lancaster, PA, USA.
Org Biomol Chem. 2013 Sep 28;11(36):5994-7. doi: 10.1039/c3ob41365a.
Bicyclo[3.2.0]hept-2-enes undergo thermal rearrangement to norbornenes via diradical transition structures. The synthesis of exo-7-cyclopropylbicyclo[3.2.0]hept-2-ene has been achieved by cycloaddition of cyclopentadiene and cyclopropylketene, generated by treatment of cyclopropylacetyl chloride with triethylamine. A comparison of the cyclopropyl substituent effect with that of other C7 substituents provides experimental evidence of an electron-donating conjugative effect on the transient diradical transition structure in the thermal reaction of exo-7-cyclopropylbicyclo[3.2.0]hept-2-ene.
双环[3.2.0]庚-2-烯经自由基过渡态热重排转化为降冰片烯。通过环戊二烯与环丙基乙烯酮的加成反应，生成了外-7-环丙基双环[3.2.0]庚-2-烯，环丙基乙酰氯与三乙胺反应生成环丙基乙烯酮。对环丙基取代基效应与其他 C7 取代基效应的比较为外-7-环丙基双环[3.2.0]庚-2-烯热反应中瞬态自由基过渡态的电子给体共轭效应提供了实验证据。
