Catalyst-Free One-Pot Access to Pyrazoles and Disulfide-Tethered Pyrazoles via Deamidative Heteroannulation of β-Ketodithioesters with Semicarbazide Hydrochloride in Water
作者:Suvajit Koley、Sumit Kumar Panja、Sonam Soni、Maya Shankar Singh
DOI:10.1002/adsc.201701595
日期:2018.5.2
operationally simple, mild, and catalyst‐free one‐pot protocol to access privileged pyrazoles and disulfide‐tethered pyrazoles has been devised by [3+2] heteroannulation of β‐ketodithioesters with semicarbazide hydrochloride in water under open air. The pH of the medium played a key role toward the selectivity switch, as refluxing in water led to the formation of pyrazoles, whereas addition of sodium acetate
通过[3 + 2]将β-酮基二硫代酯与氨基脲在水中在露天条件下[3 + 2]异环化反应,已设计出一种操作简单,温和且无催化剂的单罐方案,可访问特权吡唑和二硫键联吡唑。介质的pH值对选择性的转换起着关键作用,因为在水中的回流导致吡唑的形成,而在水中加入乙酸钠则可以形成二硫键连接的吡唑。值得注意的是,该方案涉及胺化/环化/脱水/加氢脱硫/水解/脱酰胺反应的串联序列。概述了该区域/化学选择性多米诺反应的机理原理,该原理得到密度泛函理论计算的充分支持和验证。