K2CO3-Mediated Synthesis of Functionalised 4-Substituted-2-amino-3-cyano-4H-chromenes via Michael-Cyclization Reactions

Abstract

An efficient approach for the synthesis of functionalized 4-substituted-2-amino-3-cyano-4H-chromenes moderate to high yields (up to 98%) has been achieved via a tandem K2CO3 catalyzed conjugate addition-cyclization reaction of malononitrile and a range of Knoevenagel adducts previously formed from oxindole, pyrazolone, nitromethane, N,N-dimethylbarbituric acid or indanedione. This methodology differs from the previous classical methods in its simplicity and ready availability of the catalyst.

Advancements in the Preparation of 4H‐Chromenes: An Overview

“…However, in 2014, Shi and Zhang reported a Michael addition triggered cascade reaction of malononitrile with Knoevenagel adducts generated from salicylaldehyde and nucleophiles (Scheme 63). [61] They found the use of K 2 CO 3 could allow the in situ formation of o ‐QMs from o ‐hydroxy styrenes (Knoevenagel adducts) originated from oxindole, pyrazolone, nitromethane, N , N ‐dimethylbarbituric acid and indanedione, which then underwent tandem Michael addition with malononitrile and subsequent cyclization to provide functionalized 4‐substutited‐3‐cyano‐4 H ‐chromenes 238 in high yields (Scheme 63). 1:1 dr was obtained for almost all substrates except for o ‐hydroxy styrene derived from 2‐ naphthol and isatin (>20:1 dr).…”

An Efficient and Ecofriendly Three-Component Reaction for the Rapid Synthesis of 2-Amino-4H-chromenes Catalyzed by a DABCO­-Based Ionic Liquid

“…Calcd for C 18 H 12 N 4 O 3 : C, 65.06; H, 3.64;N,16.86. Found: C,65.17;H,3.73;N,16.94. Amino-6,8-dibromo-4-(1H-indol-3-yl) 2, 56.7, 111.0, 112.4, 116.4, 118.2, 118.5, 119.3, 120.5, 121.4, 124.0, 125.4, 128.3, 131.5, 133.7, 137.3, 145.3, 160.0.…”

Highly Efficient One‐Pot Three‐Component Synthesis and Antimicrobial Activity of 2‐Amino‐4H‐chromene Derivatives

“…Among various derivatives of chromene, 2‐amino‐4 H ‐chromenes have attracted great attention, as they present wide range of biological functions such as antimicrobial , antifungal , antitumor , anticancer , antioxidant , antileishmanial , inhibitors , and hypotensive activities. In recent years, several new methodologies have been developed to synthesize 4 H ‐chromene derivatives by means of acidic and basic catalysis , CuO─CeO 2 nanocomposite , catalyst‐free conditions in water , ionic liquid , ultrasonic , and microwave irradiations along with grinding . Despite all of these new modifications, the majority of the reactions have rather low or moderate yields and often produce significant amounts of byproducts.…”