Highly diastereoselective annulation of 2-substituted 3-nitro-2H-chromenes with hemicurcuminoids and curcuminoids via a double and triple Michael reaction cascade

Abstract

The K2CO3-catalysed double Michael addition of (E)-1,5-diaryl- and 1-alkyl-5-arylpent-4-ene-1,3-diones to 2-trifluoromethyl- and 2-phenyl-substituted 3-nitro-2H-chromenes in dichloromethane at room temperature for 48 h results in 10-aroyl(acyl)-7-aryl-6a-nitro-6,6a,7,8,10,10a-hexahydro-9H-benzo[c]chromen-9-ones in 75-98% yields as individual...

The Michael donor–acceptor reactivity of curcumins in the synthesis of diverse multi-functional scaffolds

“…A similar report was published by Sosnovskikh's group prior to our report and mainly CF 3 and Ph-substituted nitrochromenes 38 were utilized to synthesize tetrahydrobenzochromenes 40 in the presence of catalytic amount of Cs 2 CO 3 whereas hexahydrochromenochromenones 42 (condition A) were synthesized using Cs 2 CO 3 in CH 2 Cl 2 (condition B) or CHCl 3 (condition C) under reflux conditions but the obtained products were a mixture of diastereomers in few cases. 45 To date, asymmetric reactions with curcumins have been scarcely explored and, to fill this gap, our group introduced an enantioselective reaction of curcumin 23 with 3-alkylideneoxindole carboxylates 43, which offered spirocyclic compounds 44 in the presence of cinchonine derived thiourea catalyst C5 (Scheme 13). 46 The racemic product 44 was synthesized using TMG as base and CH 3 CN as solvent.…”

Recent Advances of Michael/hetero‐Michael Addition Reaction in the Synthesis of 3‐Nitro‐2H‐chromene Derivatives

“…So, at this point, after protonation, the Michael adduct B was generated and loss of HNO 3 provided the cine‐substitution product 60 (Scheme 15). [60] …”

Hemicurcuminoids (1-styryl-1,3-diketones) – valuable multi-faceted building blocks for organic synthesis

“…The analogous double Michael cascade involving 5-arylpentene-1,3-diones 1 , 2 and 2-substituted 3-nitro-2 H -chromenes 94 has been studied by our group. 119 We have synthesised a large library of hexahydro-6 H -benzo[ c ]chromenes 95 and performed their modification into pyrazoles 96 . The usage of potassium carbonate as a base led to the target products 95 in nearly quantitative yields.…”