Michael condensation of 3-arylidene-3H-pyrrol-2-ones and 3-arylidene-3H-furan-2-ones with cyclohexanone

Abstract

The Michael condensation in the series of 5-aryl-3-arylidene-3H-pyrrol-2-ones and 5-aryl-3-arylidene-3H-furan-2-ones, containing an activated C=C bond, with cyclohexanone was investigated. It was shown that the condensation products were 1,5-dicarbonyl compounds containing a heterocyclic fragment. The enolization of one of the oxo groups, leading to the formation of hydroxypyrrole or hydroxyfuran structures, was demonstrated by the spectral data.It is possible to obtain acyclic and semi-and bicyclic ketones with symmetrical and unsymmetrical structures by the Michael reaction. This condensation is of great value since it makes it possible to increase the length of a carbon chain and to introduce various substituents into the structure of the investigated compounds in a single stage.Transformations based on Michael condensation with heterocyclic compounds as addends were examined in the series of 5-pyrazolones [1], pyrones [2], and 5-R-3H-furan-2-ones [3]. However, there are no data on the use of unsaturated five-membered heterocycles as acceptors in the Michael reaction. The structures of 3-arylidene-3H-furan-2-ones and 3-arylidene-3H-pyrrol-2-ones contain an activated double bond. As demonstrated earlier [4], the C=C and C=O bonds are fixed in the S-cis-configuration, which makes it possible to use them as acceptors in Michael condensation. We introduced cyclohexanone as addend. O R X O Ar EtOH O R X OH Ar + 4a,b-6a,b 1a,b-3a,b 1-6 R = C 6 H 4 Me; 1, 4 X = N-Ph, a Ar = Ph, b Ar = C 6 H 4 OMe-p; 2, 5 X = N-H, a Ar = Ph, b Ar = C 6 H 4 NMe 2 -p; 3, 6 X = O, a Ar = C 6 H 4 NO 2 -m, b Ar = C 6 H 4 OH-pThe Michael condensation in the series of 3-arylidene-3H-pyrrol-2-ones 1, 2 was realized at 60-65°C under the conditions of base catalysis (piperidine) with ethanol as solvent. N-Phenyl-3-(aryl-2-cyclohexanonylmethyl)-2-hydroxy-5-(4-methylphenyl)pyrroles 4a,b and 3-(aryl-2-cyclohexanonylmethyl)-2-hydroxy-5-(4-methylphenyl)pyrroles 5a,b were isolated with yields of up to 70% (Table 1).

Structure, Z′ = 2 Crystal Packing Features of 3-(2-Chlorobenzylidene)-5-(p-tolyl)furan-2(3H)-one

“…Arylmethylidene derivatives are also available as scaffolds for the synthesis of various heterocyclic compounds of different complexity. These substances combine the properties of unsaturated carbonyl compounds and esters, allowing the implementation of reactions with various C-nucleophiles such as acetoacetic ester [ 18 ], acetylacetone [ 19 ], cyclohexanone [ 20 ], and mono- and N , N -binucleophiles [ 21 , 22 ]. Owing to the presence of a conjugated double bond, arylidene derivatives can easily add azides [ 23 , 24 ] oxygen (to give rise corresponding epoxides [ 25 ]), and halogen [ 26 ].…”