Compounds 3 are red crystal substances readily soluble in DMSO and DMF, poorly soluble in other common organic solvents, and insoluble in saturated hydrocarbons and water. The products give a positive test (cherry-red coloration) with iron(III) chloride for the presence of enol hydroxyl groups. The IR spectra of 3 have absorption bands inherent to stretching vibrations of the enolic hydroxy group (3161–3188 cm−1, broadened band), two lactam carbonyl groups C5'=O (1763–1781 cm−1) and C2=O (1715–1732 cm−1), and two ketone carbonyl moieties C4=O (1667–1680 cm−1) and C3'-C=O (1640–1647 cm−1).
1H-NMR spectra of 3 display signals of protons in the aromatic rings and substituents attached thereto, two doublets from the protons of the ethylene fragment of the cinnamoyl substituent (δ 7.64–7.66 and 7.72–7.75 ppm) with coupling constant (3J) values of about 16 Hz, and a broadened singlet from the enolic hydroxy proton (δ 13.31–13.45 ppm). In the 13C-NMR spectra of 3d we have observed carbon atom signals of the aromatic and aliphatic fragments, the carbonyl carbon atom of the cinnamoyl moiety (δ 182.46 ppm), ketone carbonyl carbon atom C4 (δ 183.74 ppm), lactam carbonyl carbon atoms C2 (δ 171.89 ppm) and C5' (δ 165.38 ppm), and spiro carbon atom (δ 68.34 ppm).
The structure of 3c was unambiguously confirmed by single-crystal X-ray crystallography (Figure 1 and Figure 2).
3'-Cinnamoyl-4'-hydroxy-1,1'-di(4-methylphenyl)-1H-spiro[indeno[1,2-b]pyrrole-3,2'-pyrrole]-2,4,5'(1'H)-trione (3c): Red solid, yield 79%, mp 282–283 °C. IR νmax: 3174 (OH), 1763 (C2=O), 1727 (C5'=O), 1678 (C4=O), 1647 (C3'-C=O) cm−1. 1H-NMR δ: 2.28 (s, 3H, Me), 2.43 (s, 3H, Me), 6.39 (d, 1H, H-8, J = 7.3 Hz), 7.01–7.69 (m, 16H, H-arom), 7.64 (d, 1H, COCH=CHPh, J = 15.8 Hz), 7.74 (d, 1H, COCH=CHPh, J = 15.8 Hz), 13.31 (s, 1H, OH).
Molecules 2012, 17(12), 13787-13794; doi:10.3390/molecules171213787