Ionic Liquid Promoted Regio‐Selective Synthesis of 2‐Methyl amino‐3‐Nitro‐pyrano[3,2‐c]chromen‐5‐ones

Abstract

An efficient, and simple protocol for the synthesis of extremely functionalized pyrano[3,2‐c]chromen‐5‐ones (4 a–v) has been developed. One‐pot multicomponent cyclo‐condensation of 4‐hydroxycoumarin, aromatic‐aldehydes, and (E)‐N‐methyl‐1‐(methylthio)‐2‐nitroethenamine (NMSM) catalyzed by ionic liquid [(EMIM)Ac] in two different methods as methanolic mediated and at solvent free condition is described which presumably involve the Knoevenagel reaction succeeding Michael‐addition and O‐cyclization with elimination of methanethiol. The noteworthy features of this protocol are use of ionic liquid as catalyst, good to excellent yield, optimum reaction time with easy experimental procedure. The prepared derivatives were characterized by IR, 1HNMR,13CNMR and HRMS spectroscopic techniques.

The Synthesis of Nitrogen- and Oxygen-Containing Heterocyclic Scaffolds Assisted by Ionic Liquids: A 2022 Literature Survey

“…Katariya et al developed a protocol for 1-ethyl-3-methylimidazolium acetate [Emim][Ac] catalysed synthetic construction of 4-hydroxycoumarin (53), aldehydes (87) and (E)-N-methyl-1-(methylthio)-2-nitriethenamine (98) to form pyrano[3,2-c]chromen-5-ones (99) under solvent free conditions in moderate to excellent yields (Scheme 30). 86 The ILs catalysed protocol was claimed superior as compared to the previously reported protocols. 87 This article is protected by copyright.…”

“…Katariya and co-workers have developed a protocol for the 1-ethyl-3-methylimidazolium acetate [Emim][Ac]-catalyzed synthetic construction of pyrano[3,2-c]chromen-5ones 99 in moderate to excellent yields from 4-hydroxycoumarin (53), aldehydes 87 and (E)-N-methyl-1-(methylthio)-2-nitriethenamine (98) under solvent-free conditions (Scheme 30). 87 This IL-catalyzed protocol was claimed to be superior compared to previously reported protocols. [88][89][90] Scheme 30 Synthesis of pyrano[3,2-c]chromen-5-ones 99 catalyzed by imidazolium-based ILs…”