The coordination chemistry of ring-contracted porphyrinoids, such as subporphyrins and calix[3]pyrroles, has been largely unexplored owing to the synthetic difficulty of their free-base analogues. Here, we report strain-based molecular design and high-yield synthesis of thiazole-containing calix[3]pyrrole analogues for metal complexation. The artificial force induced reaction and StrainViz analysis methods were used to perform a conformational search and evaluate/visualize the ring strain. The results indicated that the thiazole-containing analogues are less strained than the parent calix[3]pyrrole, while incorporation of imidazole or oxazole unexpectedly leads to an increase in the total strain. Calix[1]furan[2]thiazole was obtained in 60% yield by the direct macrocyclization between α-bromoketone and bis(thioamide), whereas the meso-N(sp²)-bridged analogue, which was calculated to be 5.1 kcal mol⁻¹ more strained, was only obtained in a 2% yield. Calix[1]furan[2]thiazole was converted to calix[1]pyrrole[2]thiazole to investigate metal complexation. Through the reaction with Et₂Zn, calix[1]pyrrole[2]thiazole bound a Zn(II) ion in a tridentate fashion adopting a cone conformation, giving a water/air stable organozinc complex that catalyzes polymerization of lactide. Conversely, Ag(I) and Pd(II) ions coordinated to the partial cone conformation of calix[1]pyrrole[2]thiazole in a bidentate fashion. Strain-based molecular design expands the synthetic access to contracted porphyrinoids and provides the opportunity to take advantage of their rich coordination chemistry.

中文翻译：

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含噻唑杯[3]吡咯类似物的基于应变的设计、直接大环化和金属络合

由于游离碱类似物的合成困难，缩环卟啉类化合物（例如亚卟啉和杯[3]吡咯）的配位化学在很大程度上尚未得到探索。在这里，我们报告了基于菌株的分子设计和用于金属络合的含噻唑的杯[3]吡咯类似物的高产率合成。使用人工力诱导反应和 StrainViz 分析方法来执行构象搜索并评估/可视化环应变。结果表明，含噻唑类似物的应变小于母体杯[3]吡咯，而咪唑或恶唑的掺入出人意料地导致总应变增加。通过α-溴酮和双(硫代酰胺)之间的直接大环化反应，得到了Calix[1]呋喃[2]噻唑，产率为60%，而内消旋-N(sp ² )-桥接类似物，经计算为5.1 kcal mol ^-1更紧张，仅以 2% 的产率获得。将杯[1]呋喃[2]噻唑转化为杯[1]吡咯[2]噻唑以研究金属络合。通过与Et ₂ Zn反应，杯[1]吡咯[2]噻唑以锥形构象的三齿形式结合Zn( II )离子，得到水/空气稳定的有机锌配合物，催化丙交酯的聚合。相反，Ag( I )和Pd( II )离子以二齿方式与杯[1]吡咯[2]噻唑的部分圆锥构象配位。基于应变的分子设计扩大了收缩卟啉类化合物的合成途径，并提供了利用其丰富的配位化学的机会。