Robinson Emily R T, Walden Daniel M, Fallan Charlene, Greenhalgh Mark D, Cheong Paul Ha-Yeon, Smith Andrew D
EaStCHEM , School of Chemistry , University of St Andrews , North Haugh , St Andrews KY16 9ST , UK . Email:
Department of Chemistry , Oregon State University , 135 Gilbert Hall , Corvallis , OR 97331 , USA . Email:
Chem Sci. 2016 Dec 1;7(12):6919-6927. doi: 10.1039/c6sc00940a. Epub 2016 Jul 4.
Isothiourea-catalyzed annulations between 2-acyl benzazoles and α,β-unsaturated acyl ammonium intermediates are selectively tuned to form either lactam or lactone heterocycles in good yields (up to 95%) and high ee (up to 99%) using benzothiazole or benzoxazole derivatives, respectively. Computation gives insight into the significant role of two 1,5-S···O interactions in controlling the structural preorganization and chemoselectivity observed within the lactam synthesis with benzothiazoles as nucleophiles. When using benzazoles the absence of a second stabilizing non-bonding 1,5-S···O interaction leads to a dominant C-H···O interaction in determining structural preorganization and lactone formation.
异硫脲催化的2-酰基苯并唑与α,β-不饱和酰基铵中间体之间的环化反应，分别使用苯并噻唑或苯并恶唑衍生物，可以选择性地调节反应，以良好的产率（高达95%）和高对映体过量（高达99%）形成内酰胺或内酯杂环。计算结果揭示了两个1,5-S···O相互作用在控制以苯并噻唑为亲核试剂的内酰胺合成中所观察到的结构预组织和化学选择性方面的重要作用。当使用苯并唑时，由于不存在第二个稳定的非键1,5-S···O相互作用，导致在决定结构预组织和内酯形成方面，C-H···O相互作用起主导作用。
