C3-Symmetric cinchonine-squaramide as a recyclable efficient organocatalyst for tandem Michael addition–cyclisation of malononitrile and nitrovinylphenols

The chemistry of 2-hydroxy-β-nitrostyrenes: versatile intermediates in synthetic organic chemistry

“…This reaction is well tolerated with both electron-donating and electron-withdrawing substituents on the phenyl ring of 2 as well as polyaromatic nitrovinyl phenols. 69 Recently, Valle and colleagues prepared various polymeric organocatalysts by grafting chiral bifunctional thioureas and squaramides into the polymers of intrinsic microporosity. The prepared polymeric catalysts were applied in the reaction of 2 with malononitrile in CH 2 Cl 2 at rt to afford the corresponding 2-amino-3-cyano-4-nitromethyl-4H-chromene 174 in high yields (68-83%) and moderate enantioselectivities (up to 80 : 20 er).…”

“…This reaction is well tolerated with both electron-donating and electron-withdrawing substituents on the phenyl ring of 2 as well as polyaromatic nitrovinyl phenols. 69…”

Synthesis of C3-Symmetric Cinchona-Based Organocatalysts and Their Applications in Asymmetric Michael and Friedel–Crafts Reactions

“…Csámpai and co-workers examined the in vitro antitumor activity of acylated mono-, bis-, and tris-cinchona-based amines [26]. Other than high selectivity, Dong et al also showed the good recyclability of cinchonine squaramide-based C 3 -symmetric catalysts in enantioselective Michael addition, in hydroxyalkylation of indoles with alkyl trifluoropyruvate, and in asymmetric chlorolactonization of carboxylic acids [27][28][29][30]. These catalysts were easily recovered by precipitation and used for four to six cycles without significant loss of productivity or selectivity.…”

Organocascade Synthesis of Spiro[chroman‐3,2′‐indanedione] Scaffolds via [4+2] or [1+1+4] Cyclisation

“…Whereas, ( E )‐2‐(2‐nitrovinyl)phenol acts as a 1,4‐ambiphilic substrate, in various cascade, [12] triple cascade, [13] quadruple cascade [14] and quintuple cascade [15] reactions. These cascade reactions were initiated via either Michael or Oxa‐Michael addition followed by Michael, [16] acetalisation, [17] hemiacetalisation, [18] hemiketalisation, [19] lactonisation, [20] aldol, [21] cyclisation, [22] iodisation [23] etc. Due to its 1,4‐ambiphilic reactivity, it has intrigued organic chemists in designing various chromans, [24] chromenes, [25] α‐keto‐esters, [26] benzofurans [27] and coumarins [28] …”