Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province, Gannan Normal University, Ganzhou 341000, China.
J Org Chem. 2021 Jun 18;86(12):8365-8380. doi: 10.1021/acs.joc.1c00783. Epub 2021 Jun 7.
A new photocatalyst-free visible-light-enhanced strategy for the synthesis of pyrazolo[1,5-][1,3,5]triazine-2,4-diamines via the formation of electron donor-acceptor (EDA) complexes is reported. The generated pyrazolthiourea intermediates from 1-pyrazol-3-amines and isothiocyanates undergo formal [4 + 2] annulation with 1,1,3,3-tetramethylguanidines (TMG) to deliver the corresponding products involved in three C-N bond formations in a one-pot protocol. The formation of EDA complex from pyrazolthiourea and TMG is confirmed by UV-vis spectroscopy and H NMR experiments. Moreover, this mild reaction proceeds in the absence of any external transition metals, oxidants, bases, and ligands. This efficient methodology for the synthesis of purine analogues pyrazolo[1,5-][1,3,5]triazine-2,4-diamines provides potential synthetic applications in the field of drug research and development.
本文报道了一种新型的无 photocatalyst 可见光增强策略，通过形成电子给体-受体（EDA）复合物，用于合成吡唑并[1,5-][1,3,5]三嗪-2,4-二胺。由 1-吡唑-3-胺和异硫氰酸酯生成的生成的吡唑硫脲中间体与 1,1,3,3-四甲基胍（TMG）进行形式上的[4 + 2]环加成反应，以一锅法协议提供涉及三个 C-N 键形成的相应产物。通过 UV-vis 光谱和 H NMR 实验证实了吡唑硫脲和 TMG 之间形成 EDA 复合物。此外，该温和的反应在没有任何外部过渡金属、氧化剂、碱和配体的情况下进行。这种用于合成嘌呤类似物吡唑并[1,5-][1,3,5]三嗪-2,4-二胺的有效方法为药物研发领域提供了潜在的合成应用。
