A 3,5 a -epoxyfuro[2,3,4- de ]isoquinoline scaffold, the product of ROCM of 1,4:5,8-diepoxynaphthalenes, is a promising antiproliferative agent toward breast and prostate human cancer cell lines.

The asymmetric unit of the title compound, 2C₃₁H₂₈N₂O₄S·C₂H₆O, contains a parent molecule and a half molecule of ethanol solvent. The main compound stabilizes its molecular conformation by forming a ring with an R ₁ ²(7) motif with the ethanol solvent molecule. In the crystal, molecules are connected by C—H...O and O—H...O hydrogen bonds, forming a three-dimensional network. In addition, C—H...π interactions also strengthen the molecular packing.

It has been proved that the reaction between furfuryl amines and N-R-maleimides leads to the formation of aza-Michael addition products – 3-(furylmethylamino)-N-R-pyrrolidine-2,5-diones, instead of 7-oxa-2-azabicyclo[2.2.1]hept-5-enes, as this journal reported previously.

The chiral title compounds, C₂₁H₁₈N₂O₂, (I), and C₂₁H₁₈N₂OS, (II) – products of the three-component reaction between benzylamine, isatoic anhydride and furyl- or thienyl-acrolein – are isostructural and form isomorphous racemic crystals. The tetrahydropyrimidine ring in (I) and (II) adopts a sofa conformation. The amino N atom has a trigonal–pyramidal geometry [sum of the bond angles is 347.0° for both (I) and (II)], whereas the amido N atom is flat [sum of the bond angles is 359.3° for both (I) and (II)]. The furyl- and thienylethenyl substituents in (I) and (II) are planar and the conformation about the bridging C=C bond isE. These bulky fragments occupy the axial position at the quaternary C atom of the tetrahydropyrimidine ring, apparently, due to steric reasons. In the crystals, molecules of (I) and (II) form hydrogen-bonded helicoidal chains propagating along [010] by strong intermolecular N—H...O hydrogen bonds.

Compounds (I), C₂₂H₂₀N₂O₂, (II), C₂₂H₂₀N₂O₂ and (III), C₂₀H₁₈N₂O₃ are the products of three-component reactions between isatoic anhydride, the corresponding amine and 3-(5-methylfuran-2-yl)- or (furan-2-yl)-2-methylacrylaldehyde. Compound (I) crystallizes in the monoclinic space group P2₁/n, while compounds (II) and (III) are isostructural and crystallize in the orthorhombic space group Pbca. The tetrahydropyrimidine ring in (I)–(III) adopts a sofa conformation. The NH nitrogen atom has a trigonal–pyramidal geometry, whereas the N(R) nitrogen atom is flattened. The furyl-vinyl substituents in (I)–(III) are practically planar and have an E configuration at the C=C double bond. In (I), this bulky fragment occupies the axial position at the quaternary carbon atom of the tetrahydropyrimidine ring, whereas in (II) and (III) it is equatorially disposed. In the crystal of (I), molecules form hydrogen-bonded chains propagating along [001] by strong intermolecular N—H...O hydrogen bonds. The chains are packed in stacks along the a-axis direction. In the crystals of (II) and (III), molecules also form hydrogen-bonded chains propagating along [100] by strong intermolecular N—H...O hydrogen bonds. However, despite the fact that compounds (II) and (III) are isostructural, steric differences between the phenyl and furyl substituents result in chains with different geometries. Thus in the crystal of (II) the chains have a zigzag-like structure, whereas in the crystal of (III), they are almost linear. In both (II) and (III), the hydrogen-bonded chains are further packed in stacks along the b-axis direction.