Reactions of arylazosulfones with the conjugate bases of (tert-butoxycarbonyl)methyl and tosylmethyl isocyanide. Synthesis of substituted 1-arylimidazoles
The reactions of arylazosulfones 1 (ArN=NSO2Ar') with the potassium salts of (tert-butoxycarbonyl)methyl 2 and tosylmethyl isocyanide 3 in DMSO afford 4,5-bis(tert-butoxycarbonyl)-4 and 4-tosyl-1-arylimidazoles 5, respectively. Yields of imidazoles 4 and 5 vary from moderate to excellent depending on the nature both of Ar in 1 and of the nucleophile (2 or 3) employed. A comparison of the results obtained with those relevant to the reactions of the same nucleophiles with nitrosobenzene in analogous experimental conditions provides useful mechanistic indications on the transformation of 1 to 4 or 5. (C) 1997, Elsevier Science Ltd.
Silver‐Catalyzed [3+1+1] Annulation of Nitrones with Isocyanoacetates as an Approach to 1,4,5‐Trisubstituted Imidazoles
作者:Lanlan Lv、Yan Chen、Andrey Shatskiy、Jian‐Quan Liu、Xiaoyi Liu、Markus D. Kärkäs、Xiang‐Shan Wang
DOI:10.1002/ejoc.202001536
日期:2021.2.12
A silver‐catalyzed protocol for [3+1+1] annulation of nitrones and isocyanoacetates is reported. The reaction is proposed to proceed through sequential [3+2] cycloaddition, ring‐opening, cyclization‐oxidation, and dealkylation, allowing access to a broad scope of valuable polysubstituted imidazoles in high yields.