Wang Xiao-Na, Krenske Elizabeth H, Johnston Ryne C, Houk K N, Hsung Richard P
†School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, Henan 450001 P. R. China.
‡Division of Pharmaceutical Sciences and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53705 United States.
J Am Chem Soc. 2015 Apr 29;137(16):5596-601. doi: 10.1021/jacs.5b02561. Epub 2015 Apr 20.
We report the first experimental evidence for the generation of highly strained cis,trans-cycloheptadienones by electrocyclic ring opening of 4,5-fused cyclobutenamides. In the presence of AlCl3, the cyclobutenamides rearrange to [2.2.1]-bicyclic ketones; DFT calculations provide evidence for a mechanism involving torquoselective 4π-electrocyclic ring opening to a cis,trans-cycloheptadienone followed by a Nazarov-like recyclization and a 1,2-alkyl shift. Similarly, 4,6-fused cyclobutenamides undergo AlCl3-catalyzed rearrangements to [3.2.1]-bicyclic ketones through cis,trans-cyclooctadienone intermediates. The products can be further elaborated via facile cascade reactions to give complex tri- and tetracyclic molecules.
我们报道了通过4,5-稠合环丁烯酰胺的电环化开环生成高张力顺式、反式环庚二烯酮的首个实验证据。在AlCl₃存在下，环丁烯酰胺重排为[2.2.1]双环酮；密度泛函理论计算为一种机制提供了证据，该机制涉及对映选择性4π-电环化开环生成顺式、反式环庚二烯酮，随后是类似纳扎罗夫的环化反应和1,2-烷基迁移。同样，4,6-稠合环丁烯酰胺通过顺式、反式环辛二烯酮中间体进行AlCl₃催化的重排反应生成[3.2.1]双环酮。这些产物可通过简便的级联反应进一步转化为复杂的三环和四环分子。
