This manuscript reports the synthesis and X-ray characterization of two octahydro-1H-4,6-epoxycyclopenta[c]pyridin-1-one derivatives that contain the four most abundant halogen atoms (Ha) in the structure with the aim of studying the formation of Ha···Ha halogen bonding interactions. The anisotropy of electron density at the heavier halogen atoms provokes the formation of multiple Ha···Ha contacts in the solid state. That is, the heavier Ha-atoms exhibit a region of positive electrostatic potential (σ-hole) along the C–Ha bond and a belt of negative electrostatic potential (σ-lumps) around the atoms. The halogen bonding assemblies in both compounds were analyzed using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, the quantum theory of “atom-in-molecules” (QTAIM), the noncovalent interaction plot (NCIplot), and the electron localization function (ELF).

A series of 4,5-dibromo-2-(4-substituted phenyl)hexahydro-3a,6-epoxyisoindol-1(4H)-ones were synthesized by reaction of the corresponding 2-(4-substituted phenyl)-2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1(6H)-ones with [(Me₂NCOMe)₂H]Br₃ in dry chloroform under reflux for 3−5 h. In contrast to the 4-F and 4-Cl substituents, one of the bromine atoms of the isoindole moiety behaves as a halogen bond donor in the formation of intermolecular halogen bonding in the 4-H, 4-Br and 4-I analogues. Not only intermolecular hydrogen bonds, but also Ha⋯Ha and Ha⋯π types of halogen bonds in the 4-H, 4-Br, and 4-I compounds, contribute to the formation of supramolecular architectures leading to 2D or 3D structures.

In the title compounds, N,N-dimethylacetamide–1-(dimethyl-λ⁴-azanylidene)ethan-1-ol tribromide (1/1), C₄H₉NO·C₄H₁₀NO⁺·Br₃ ⁻ or [(C₄H₉NO)·(C₄H₁₀NO)](Br₃), (I), N,N-dimethylacetamide–1-(dimethyl-λ⁴-azanylidene)ethan-1-ol dibromidoiodate (1/1), C₄H₉NO·C₄H₁₀NO⁺·Br₂I⁻ or [(C₄H₉NO)·(C₄H₁₀NO)](Br₂I), (II), and N,N-dimethylacetamide–1-(dimethyl-λ⁴-azanylidene)ethan-1-ol dichloridoiodate (1/1), C₄H₉NO·C₄H₁₀NO⁺·Cl₂I⁻ or [(C₄H₉NO)·(C₄H₁₀NO)]·(Cl₂I), (III), all the anions are almost linear in geometry and all the cations, except for the methyl H atoms, are essentially planar. In the crystal structure of (I), the cations are linked by pairs of C—H...O hydrogen bonds, forming inversion dimers with an R ₂ ²(8) ring motif. These dimers also exhibit O—H...O hydrogen bonding. Dimerized cation pairs and anions are arranged in columns along the a axis. In the crystal of (II), the cations are linked by pairs of O—H...O and C—H...O hydrogen bonds, forming an R ₄ ⁴(14) ring motif. These groups of cations and the anions form individual columns along the a axis and jointly reside in planes roughly parallel to (011). In the crystal of (III), cations and anions also form columns parallel to the a axis, resulting in layers parallel to the (020) plane. Furthermore, the crystal structures of (I), (II) and (III) are consolidated by strong halogen (Br and/or I and/or Cl)...H and weak van der Waals interactions. In addition to the structural evaluation, a Hirshfeld surface analysis was carried out.

A series of amino derivatives of 5-arylisoxazoles and 4,5-dichloroisothiazole with primary and secondary amino groups was synthesized. 3-Aminomethyl-5-arylisoxazol-3-ylmethanamines were obtained on the basis of 5-aryl-3-(chloromethyl)isoxazoles using the Gabriel phthalimide method. 5-Arylisoxazol-3-yl- and 4,5-dichloroisothiazol-3-ylallylamines were synthesized in two ways: reduction of azomethines obtained by condensation of 5-arylisoxazolyl- and 4,5-dichloroisothiazolyl-3-carbaldehydes with allylamine, and by nucleophilic substitution of the chlorine atom in 3-chloromethyl derivatives of the corresponding azoles by reaction with allylamine. Amides and sulfonamides of azolylallylamines were synthesized. Some of the compounds obtained showed antibacterial and fungicidal activity.

The title compounds C₂₄H₂₁NO₃S, I, and C₂₄H₂₁NO₄, II, are the products of the IMDAV reaction between phenylmaleic anhydride and thienyl(furyl)allylamines. Their molecular structures comprise fused tricyclic systems containing thiophene, cyclohexene and pyrrolidine rings (I) or furan, cyclohexene and pyrrolidine rings (II). The central cyclohexene and pyrrolidine rings in both compounds adopt slightly twisted boat and envelope conformations, respectively. The dihedral angles between the basal plane of the pyrrolidine ring and the thiophene (in I) or furan (in II) ring plane are 22.74 (16) and 26.29 (5)°, respectively. The nitrogen atom both in I and II has practically planar environment [the sums of the bond angles are 359.8 and 358.9°, respectively]. In the crystal of I, the molecules form hydrogen-bonded zigzag chains along [010] through strong intermolecular O—H...O hydrogen bonds involving carboxylic and keto groups, whereas in the crystal of II, the molecules are joined into centrosymmetric dimers by strong O—H...O hydrogen bonds between the carboxylic groups. In II, the atoms involved into these hydrogen bonds (and hence the whole carboxylic group) are disordered over two sets of sites with an occupancy ratio of 0.6:0.4. Compounds I and II crystallize as racemates consisting of enantiomeric pairs of the 3aSR,4RS,4aRS,7aSR and 3aSR,4SR,4aRS,7aSR diastereomers, respectively.