AbstractThiourea derivatives are in‐demand motifs in organic synthesis, medicinal chemistry and material science, yet redox methods for the synthesis that start from safe, simple, inexpensive and readily available feedstocks are scarce. In this article, we disclose the synthesis of these motifs using elemental sulfur and nitromethane as the starting materials. The method harnesses the multi‐electron auto‐redox property of nitromethane in the presence of sulfur and amines, delivering thiourea products without any added oxidant or reductant. Extension of this reaction to cyclizable amines and/or higher homologues of nitromethane led to a wide range of nitrogen heterocycles and thioamides. Operationally simple, the reactions are scalable, tolerate a wide range of functional groups, and can be employed for the direct functionalization of natural products. Mechanistically, the nitro group was found to act as an oxidant leaving group, being reduced to ammonia whereas sulfur, along with the role of a sulfur building block for the thiocarbonyl group, behaved as a complementary reductant, being oxidized to sulfate.
摘要 硫脲衍生物是有机合成、药物化学和材料科学中炙手可热的基团,然而以安全、简单、廉价和易于获得的原料为起始原料的氧化还原合成方法却十分稀缺。本文披露了以元素硫和硝基甲烷为起始原料合成这些基团的方法。该方法利用了硝基甲烷在硫和胺存在下的多电子自动氧化还原特性,在不添加任何氧化剂或还原剂的情况下生成硫脲产品。将这一反应扩展到可环化胺和/或硝基甲烷的更高同系物,可得到多种氮杂环和硫代酰胺。该反应操作简单,可扩展性强,可容忍多种官能团,可用于天然产物的直接官能化。从机理上讲,硝基可作为氧化剂离去基团,被还原成氨,而硫作为硫代羰基的硫构件,可作为互补还原剂,被氧化成硫酸盐。