Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, Yayoi-cho, Inage-ku, Chiba, 263-8522 Japan.
Org Biomol Chem. 2018 Oct 31;16(42):7910-7919. doi: 10.1039/c8ob02066c.
A novel regioselective cyclization reaction of N-cinnamoylthioureas leading to six- or five-membered heterocyclic compounds was developed. N-Cinnamoylthioureas in the presence of trifluoroacetic acid (TFA) underwent the well-established intramolecular cycloaddition reaction to give 2-imino-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones in good yields. On the other hand, the reaction with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proceeded in an unprecedented "umpolung" cyclization fashion to afford five-membered 2-imino-1,3-thiazolidin-4-ones and/or 2-thioxoimidazolidine-4-ones. The reaction was considered to occur via a cycloadduct of DBU with the cinnamoyl moiety followed by intramolecular attack of the thiourea group.
发展了一种 N-肉桂酰基硫脲的新型区域选择性环化反应，生成六元或五元杂环化合物。在三氟乙酸（TFA）存在下，N-肉桂酰基硫脲经历了成熟的分子内环加成反应，以高产率得到 2-亚氨基-2,3,5,6-四氢-4H-1,3-噻嗪-4-酮。另一方面，与 1,8-二氮杂双环[5.4.0]十一-7-烯（DBU）的反应以前所未有的“反转”环化方式进行，生成五元 2-亚氨基-1,3-噻唑烷-4-酮和/或 2-硫代亚氨基咪唑烷-4-酮。该反应被认为是通过 DBU 与肉桂酰部分的环加成物，然后是硫脲基团的分子内攻击发生的。
