A novel annulation reaction of N-(het)aroyldiazenes and isothiocyanates has been established. This transformation involves a sequential cyclization and desulfurization/intramolecular rearrangement to produce 2-imino-1,3,4-oxadiazolines. The less-stable N-(het)aroyldiazenes can be conveniently generated in situ by I2-mediated oxidation of hydrazides, which allows a one-pot synthesis of the products
Synthesis of 2-Imino-1,3,4-thiadiazoles from Hydrazides and Isothiocyanates via Sequential Oxidation and P(NMe<sub>2</sub>)<sub>3</sub>-Mediated Annulation Reactions
N-acyldiazenes with isothiocyanates, producing 2-imino-1,3,4-thiadiazoles, is reported. This reaction proceeds well with crude N-acyldiazenes derived from the oxidation of hydrazides by iodine and permits the sequential synthesis of products directly from hydrazides without purification of the less stable N-acyldiazene intermediates. The reaction does not require transition metals and is a simple, scalable operation
A [4 + 3] Annulation Reaction of aza-<i>o</i>-Quinone Methides with Arylcarbohydrazonoyl Chlorides for Synthesis of 2,3-Dihydro-1<i>H</i>-benzo[<i>e</i>][1,2,4]triazepines
An unprecedented [4 + 3] annulation reaction of aza-ortho-quinone methides with arylcarbohydrazonoyl chlorides has been achieved under mild conditions. The annulation underwent a sequential conjugate addition/intramolecular annulation/rearrangement, providing a useful method for the synthesis of biologically interesting 2,3-dihydro-1H-benzo[e][1,2,4]triazepine.
在温和的条件下,已完成了氮杂-邻苯醌甲基化物与芳基羰基肼基甲酰氯的前所未有的[4 + 3]环化反应。进行连续的共轭加成/分子内的成环/重排,为生物上有趣的2,3-二氢-1 H-苯并[ e ] [1,2,4]三氮杂卓合成提供了有用的方法。
Regioselective Decarboxylative Cycloaddition Route to Fully Substituted 3‐CF
<sub>3</sub>
‐Pyrazoles from Nitrilimines and Isoxazolidinediones
作者:Yu‐Chen Tian、Jun‐Kuan Li、Fa‐Guang Zhang、Jun‐An Ma
DOI:10.1002/adsc.202100091
日期:2021.4.13
1,4‐Diaryl‐5‐carboxamido substituted 3‐trifluoromethylpyrazoles are obtained with exclusive regioselectivity under transition‐metal‐free conditions. This decarboxylative [3+2] cycloaddition protocol was enabled by employing trifluoromethyl nitrilimines as 1,3‐dipoles, and isoxazolidinediones as CO2‐masked alkynyl dipolarophiles. The applicability of this method is further manifested by its compatibility
(PBu3)-promoted annulation reaction at room temperature. In this synthetic process, crude less stable N-aroyldiazene intermediates generated by I2-mediated oxidation of hydrazides were used directly in a subsequent annulation reaction to afford the selenadiazole products. The merits of the present synthetic strategy also include absence of transition metals and gram-scale synthesis.
2-亚氨基-1,3,4-硒二唑衍生物可以在室温下通过连续氧化和三丁基膦 (PBu 3 ) 促进的环化反应从酰肼和异硒氰酸酯合成。在该合成过程中,由 I 2 -介导的酰肼氧化产生的较不稳定的粗N-芳酰基二氮中间体直接用于随后的环化反应,以提供硒二唑产物。本合成策略的优点还包括没有过渡金属和克级合成。