A series of diverse aromatic azadienetriyne and azatriynes was synthesised. These compounds were subjected to transition metal-mediated [2+2+2] cycloisomerisation to form pentacyclic or hexacyclic helically chiral azahelicene or azahelicene-like structures mostly in moderate yields. Introducing stereogenic centre(s) into selected azatriynes, cyclisation proceeded in a stereoselective fashion providing aza[5]helicenes or aza[6]helicene-like compounds in up to a 100:0 diastereomeric ratio. Gibbs energy differences between corresponding pairs of diastereomers (calculated at the DFT(B3LYP)/TZV+P level) were in good agreement with the experimental data and allowed for the prediction of the stereochemical outcome of the reaction. This study presents for the first time asymmetric synthesis of azahelicene derivatives in high optical purities.
合成了一系列多样的芳香性的偶氮二炔和偶氮三炔化合物。这些化合物经过过渡金属介导的[2+2+2]环异构化反应,形成了大部分处于中等产率下的五环或六环螺旋手性氮杂螺芴或氮杂螺芴类结构。在选定的偶氮三炔中引入立体异构中心后,环化反应以立体选择性的方式进行,提供了最高达到100:0的对映异构比例的氮杂[5]螺芴或氮杂[6]螺芴类化合物。在对应的对映异构体对之间的吉布斯自由能差异(在DFT(B3LYP)/TZV+P水平计算)与实验数据非常吻合,并可用于预测反应的立体化学结果。这项研究首次展示了高光学纯度下氮杂螺芴衍生物的不对称合成。