Polysulfonylamines. CXCI. The `almost' polymorphs rac‐trans‐2‐aminocyclohexan‐1‐aminium di(methanesulfonyl)azanide and its 0.11‐hydrate

The title compound, C₆H₁₅N₂⁺·C₂H₆NO₄S₂⁻, crystallizes as a 0.11‐hydrate, (I), in the space group C2; the asymmetric unit consists of two cations (one of each enantiomer), one anion on a general position, two half anions, each with the N atom on a twofold axis, and approximately one fifth of a water molecule. The general anion departs significantly from the usual conformation: it lacks one of the typical `W'‐shaped sequence of O—S—N—S—O atoms. The compound also crystallizes in the solvent‐free form, (II), in the space group P2₁/c, with one formula unit in the asymmetric unit. Both compounds form ribbons of hydrogen‐bonded cation dimers parallel to the b axis. In (I), there are two independent ribbons of opposite chirality, each involving one anion on a special position, and these ribbons are connected by hydrogen bonds to the anion on a general position, resulting in a layer structure parallel to (100). In (II), the chains are connected by hydrogen bonds, and again a layer structure parallel to (100) results.     

Amide hydrogen bonding: control of the molecular and extended structures of two symmetrical pyridine‐2‐carboxamide derivatives

The crystal structures of two symmetrical pyridine‐2‐carboxamides, namely N,N′‐(propane‐1,3‐diyl)bis(pyridine‐2‐carboxamide), C₁₅H₁₆N₄O₂, (I), and N,N′‐(butane‐1,4‐diyl)bis(pyridine‐2‐carboxamide), C₁₆H₁₈N₄O₂, (II), exhibit extended hydrogen‐bonded sequences involving their amide groups. In (I), conventional bifurcated amide–carbonyl (N—H)...O hydrogen bonding favours the formation of one‐dimensional chains, the axes of which run parallel to [001]. Unconventional bifurcated pyridine–carbonyl C—H...O hydrogen bonding links adjacent one‐dimensional chains to form a `porous' three‐dimensional lattice with interconnected, yet unfilled, voids of 60.6 (2) ų which combine into channels that run parallel to, and include, [001]. 4% of the unit‐cell volume of (I) is vacant. Compound (II) adopts a Z‐shaped conformation with inversion symmetry, and exhibits an extended structure comprising one‐dimensional hydrogen‐bonded chains along [100] in which individual molecules are linked by complementary pairs of amide N—H...O hydrogen bonds. These hydrogen‐bonded chains interlock viaπ–π interactions between pyridine rings of neighbouring molecules to form sheets parallel with (010); each sheet is one Z‐shaped molecule thick and separated from the next sheet by the b‐axis dimension [7.2734 (4) Å].     

Charge‐assisted hydrogen bonding in salts of 2‐amino‐1H‐benzimidazole with 3‐phenylpropynoic acid and oct‐2‐ynoic acid

The 100 K structures of two salts, namely 2‐amino‐1H‐benzimidazolium 3‐phenylpropynoate, C₇H₈N₃⁺·C₉H₅O₂⁻, (I), and 2‐amino‐1H‐benzimidazolium oct‐2‐ynoate, C₇H₈N₃⁺·C₈H₁₁O₂⁻, (II), both have monoclinic symmetry (space group P2₁/c) and display N—H...O hydrogen bonding. Both structures show packing with corrugated sheets of hydrogen‐bonded molecules lying parallel to the [001] direction. Two hydrogen‐bonded ring motifs can be identified and described with graph sets R²₂(8) and R⁴₄(16), respectively, in both (I) and (II). Computational chemistry calculations performed on both compounds show that the hydrogen‐bonded ion pairs are more energetically favourable in the crystal structure than their hydrogen–bonded neutral molecule counterparts.     

Structural comparison of three N‐(4‐halogenophenyl)‐N′‐[1‐(2‐pyridyl)ethylidene]hydrazine hydrochlorides

2‐{1‐[(4‐Chloroanilino)methylidene]ethyl}pyridinium chloride methanol solvate, C₁₃H₁₃ClN₃⁺·Cl⁻·CH₃OH, (I), crystallizes as discrete cations and anions, with one molecule of methanol as solvent in the asymmetric unit. The N—C—C—N torsion angle in the cation indicates a cis conformation. The cations are located parallel to the (02) plane and are connected through hydrogen bonds by a methanol solvent molecule and a chloride anion, forming zigzag chains in the direction of the b axis. The crystal structure of 2‐{1‐[(4‐fluoroanilino)methylidene]ethyl}pyridinium chloride, C₁₃H₁₃FN₃⁺·Cl⁻, (II), contains just one anion and one cation in the asymmetric unit but no solvent. In contrast with (I), the N—C—C—N torsion angle in the cation corresponds with a trans conformation. The cations are located parallel to the (100) plane and are connected by hydrogen bonds to the chloride anions, forming zigzag chains in the direction of the b axis. In addition, the crystal packing is stabilized by weak π–π interactions between the pyridinium and benzene rings. The crystal of (II) is a nonmerohedral monoclinic twin which emulates an orthorhombic diffraction pattern. Twinning occurs via a twofold rotation about the c axis and the fractional contribution of the minor twin component refined to 0.324 (3). 2‐{1‐[(4‐Fluoroanilino)methylidene]ethyl}pyridinium chloride methanol disolvate, C₁₃H₁₃FN₃⁺·Cl⁻·2CH₃OH, (III), is a pseudopolymorph of (II). It crystallizes with two anions, two cations and four molecules of methanol in the asymmetric unit. Two symmetry‐equivalent cations are connected by hydrogen bonds to a chloride anion and a methanol solvent molecule, forming a centrosymmetric dimer. A further methanol molecule is hydrogen bonded to each chloride anion. These aggregates are connected by C—H...O contacts to form infinite chains. It is remarkable that the geometric structures of two compounds having two different formula units in their asymmetric units are essentially the same.     

Hydrogen‐bonded assemblies of 20‐(4‐pyridyl)porphyrin‐54,104,154‐tribenzoic acid with dimethyl sulfoxide and 4‐acetylpyridine in their dimethyl sulfoxide and tetrahydrofuran solvates

Crystals of the title compounds, 20‐(4‐pyridyl)porphyrin‐5⁴,10⁴,15⁴‐tribenzoic acid–dimethyl sulfoxide (2/5), C₄₆H₂₉N₅O₆·2.5C₂H₆OS, (I), and 20‐(4‐pyridyl)porphyrin‐5⁴,10⁴,15⁴‐tribenzoic acid–4‐acetylpyridine–tetrahydrofuran (1/2/10), C₄₆H₂₉N₅O₆·2C₇H₇NO·10C₄H₈O, (II), consist of hydrogen‐bonded supramolecular chains of porphyrin units solvated by molecules of dimethyl sulfoxide [in (I)] and 4‐acetylpyridine [in (II)]. In (I), these chains consist of heterogeneous arrays with alternating porphyrin and dimethyl sulfoxide species, being sustained by COOH...O=S hydrogen bonds. They adopt a zigzag geometry and link on both sides to additional molecules of dimethyl sulfoxide. In (II), the chains consist of homogeneous linear supramolecular arrays of porphyrin units, which are directly connected to one another via COOH...N(pyridyl) hydrogen bonds. As in the previous case, these arrays are solvated on both sides by molecules of the 4‐acetylpyridine ligand via similar COOH(porphyrin)...N(ligand) hydrogen bonds. The two crystal structures contain wide interporphyrin voids, which accommodate disordered/diffused solvent molecules, viz. dimethyl sulfoxide in (I) and tetrahydrofuran in (II).     

Three different fluoro‐ or chloro‐substituted 1′‐deoxy‐1′‐phenyl‐β‐D‐ribofuranoses

Crystal structures are reported for three fluoro‐ or chloro‐substituted 1′‐deoxy‐1′‐phenyl‐β‐D‐ribofuranoses, namely 1′‐deoxy‐1′‐(2,4,5‐trifluorophenyl)‐β‐D‐ribofuranose, C₁₁H₁₁F₃O₄, (I), 1′‐deoxy‐1′‐(2,4,6‐trifluorophenyl)‐β‐D‐ribofuranose, C₁₁H₁₁F₃O₄, (II), and 1′‐(4‐chlorophenyl)‐1′‐deoxy‐β‐D‐ribofuranose, C₁₁H₁₃ClO₄, (III). The five‐membered furanose ring of the three compounds has a conformation between a C2′‐endo,C3′‐exo twist and a C2′‐endo envelope. The ribofuranose groups of (I) and (III) are connected by intermolecular O—H...O hydrogen bonds to six symmetry‐related molecules to form double layers, while the ribofuranose group of (II) is connected by O—H...O hydrogen bonds to four symmetry‐related molecules to form single layers. The O...O contact distance of the O—H...O hydrogen bonds ranges from 2.7172 (15) to 2.8895 (19) Å. Neighbouring double layers of (I) are connected by a very weak intermolecular C—F...π contact. The layers of (II) are connected by one C—H...O and two C—H...F contacts, while the double layers of (III) are connected by a C—H...Cl contact. The conformations of the molecules are compared with those of seven related molecules. The orientation of the benzene ring is coplanar with the H—C1′ bond or bisecting the H—C1′—C2′ angle, or intermediate between these positions. The orientation of the benzene ring is independent of the substitution pattern of the ring and depends mainly on crystal‐packing effects.     

3,4‐Di‐2‐pyridyl‐1,2,5‐oxadiazole and its perchlorate salt

In 3,4‐di‐2‐pyridyl‐1,2,5‐oxadiazole (dpo), C₁₂H₈N₄O, each mol­ecule resides on a twofold axis and inter­acts with eight neighbours via four C—H⋯N and four C—H⋯O inter­actions to generate a three‐dimensional hydrogen‐bonded architecture. In the perchlorate analogue, 2‐[3‐(2‐pyrid­yl)‐1,2,5‐oxadiazol‐4‐yl]pyridinium perchlorate, C₁₂H₉N₄O⁺·ClO₄⁻ or [Hdpo]ClO₄, the [Hdpo]⁺ cation is bisected by a crystallographic mirror plane, and the additional H atom in the cation is shared by the two pyridyl N atoms to form a symmetrical intra­molecular N⋯H⋯N hydrogen bond. The cations and perchlorate anions are linked through C—H⋯O hydrogen bonds and π–π stacking inter­actions to form one‐dimensional tubes along the b‐axis direction.     

An X‐ray crystallographic and density functional theory study of (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one

The Schiff base enaminones (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₃H₁₇NO₄S, (I), and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₅H₂₁NO₂, (II), were studied by X‐ray crystallography and density functional theory (DFT). Although the keto tautomer of these compounds is dominant, the O=C—C=C—N bond lengths are consistent with some electron delocalization and partial enol character. Both (I) and (II) are nonplanar, with the amino–phenol group canted relative to the rest of the molecule; the twist about the N(enamine)—C(aryl) bond leads to dihedral angles of 40.5 (2) and −116.7 (1)° for (I) and (II), respectively. Compound (I) has a bifurcated intramolecular hydrogen bond between the N—H group and the flanking carbonyl and hydroxy O atoms, as well as an intermolecular hydrogen bond, leading to an infinite one‐dimensional hydrogen‐bonded chain. Compound (II) has one intramolecular hydrogen bond and one intermolecular C=O...H—O hydrogen bond, and consequently also forms a one‐dimensional hydrogen‐bonded chain. The DFT‐calculated structures [in vacuo, B3LYP/6‐311G(d,p) level] for the keto tautomers compare favourably with the X‐ray crystal structures of (I) and (II), confirming the dominance of the keto tautomer. The simulations indicate that the keto tautomers are 20.55 and 18.86 kJ mol⁻¹ lower in energy than the enol tautomers for (I) and (II), respectively.     

Seven 5‐benzylamino‐3‐tert‐butyl‐1‐phenyl‐1H‐pyrazoles: unexpected isomorphisms,and hydrogen‐bonded supramolecular structures in zero,one and two dimensions

5‐Benzylamino‐3‐tert‐butyl‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₃N₃, (I), and its 5‐[4‐(trifluoromethyl)benzyl]‐, C₂₁H₂₂F₃N₃, (III), and 5‐(4‐bromobenzyl)‐, C₂₀H₂₂BrN₃, (V), analogues, are isomorphous in the space group C2/c, but not strictly isostructural; molecules of (I) form hydrogen‐bonded chains, while those of (III) and (V) form hydrogen‐bonded sheets, albeit with slightly different architectures. Molecules of 3‐tert‐butyl‐5‐(4‐methylbenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₁H₂₅N₃, (II), are linked into hydrogen‐bonded dimers by a combination of N—H...π(arene) and C—H...π(arene) hydrogen bonds, while those of 3‐tert‐butyl‐5‐(4‐chlorobenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₂ClN₃, (IV), form hydrogen‐bonded chains of rings which are themselves linked into sheets by an aromatic π–π stacking interaction. Simple hydrogen‐bonded chains built from a single N—H...O hydrogen bond are formed in 3‐tert‐butyl‐5‐(4‐nitrobenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₂N₄O₂, (VI), while in 3‐tert‐butyl‐5‐(3,4,5‐trimethoxybenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₃H₂₉N₃O₃, (VII), which crystallizes with Z′ = 2 in the space group P, pairs of molecules are linked into two independent centrosymmetric dimers, one generated by a three‐centre N—H...(O)₂ hydrogen bond and the other by a two‐centre N—H...O hydrogen bond.     

Supramolecular hydrogen bonding of [5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrinato]palladium(II) in the presence of competing solvents

The title porphyrin compound forms hydrogen‐bonded adducts with methanol (1:1), [Pd(C₄₈H₂₈N₄O₈)]·CH₄O, (I), and with water and N,N‐dimethylformamide (1:4:4), [Pd(C₄₈H₂₈N₄O₈)]·4C₃H₇NO·4H₂O, (II). In (I), the metalloporphyrin unit lies across a mirror plane in Cmca, while in (II), this unit lies across an inversion center in P. Extended supramolecular hydrogen‐bonded arrays are formed in (I) by intermolecular interactions between the carboxylic acid functions, either directly or through the methanol species. These layers have a wavy topology and large interporphyrin pores, which are filled in the crystal structure by double interpenetration as well as enclathration of additional non‐interacting nitrobenzene solvent molecules. The supramolecular aggregation in (II) can be characterized by cascaded porphyrin layers, wherein adjacent porphyrin molecules are hydrogen bonded to one another through molecules of water that are incorporated into the hydrogen‐bonding scheme. Molecules of dimethylformamide partly solvate the carboxylic acid groups and fill the interporphyrin space in the crystal structure.     

2‐Pyridone–tartronic acid (1/1), 3‐hydroxy­pyridinium hydrogen tartronate and 4‐hydroxy­pyridinium hydrogen tartronate

Tartronic acid forms a hydrogen‐bonded complex, C₅H₅NO·C₃H₄O₅, (I), with 2‐pyridone, while it forms acid salts, namely 3‐hydroxy­pyridinium hydrogen tartronate, (II), and 4‐hy­droxy­pyridinium hydrogen tartronate, (III), both C₅H₆NO⁺·C₃H₃O₅⁻, with 3‐hydroxy­pyridine and 4‐hydroxy­pyridine, respectively. In (I), the pyridone mol­ecules and the acid mol­ecules form R(8) and R(10) hydrogen‐bonded rings, respectively, around the inversion centres. In (II) and (III), the cations and anions are linked by N—H⋯O and O—H⋯O hydrogen bonds to form a hydrogen‐bonded chain. In each of (I), (II) and (III), an intermolecular hydrogen bond is formed between a carboxyl group and the hydroxyl group attached to the central C atom, and in (I), the hydroxyl group participates in an intramolecular hydrogen bond with a carbonyl group. No intermolecular hydrogen bond is formed between the carboxyl groups in (I), or between the carboxyl and carboxyl­ate groups in (II) and (III).     

7,7‐Di­chloro‐1,6‐di­methyl‐2‐oxa‐5‐thia­bi­cyclo­[4.1.0]­heptane 5,5‐dioxide and 6‐chloro‐2,3‐di­hydro‐7‐methyl‐5‐methyl­ene‐2H,3H,5H‐1,4‐dithiepine 1,1,4,4‐tetraoxide

The structures of a 2‐oxa‐5‐thia­bi­cyclo­[4.1.0]­heptane derivative, C₇H₁₀Cl₂O₃S, (I), and a 2H,3H,5H‐1,4‐dithiepine derivative, C₇H₉ClO₄S₂, (II), are reported. The six‐membered ring in (I) has an envelope conformation and the seven‐membered ring in (II) adopts a chair conformation. There are no untoward intermolecular interactions in (I), but two Cl atoms make a short intermolecular contact across an inversion centre in (II), with a Cl?Cl distance of 3.2784 (9) Å, some 0.22 Å less than the sum of the van der Waals radii.     

Water‐induced pseudo‐quadruple hydrogen‐bonding motifs in xanthine–inorganic acid complexes

In xanthinium nitrate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium nitrate monohydrate], C₅H₅N₄O₂⁺·NO₃⁻·H₂O, (I), and xanthinium hydrogen sulfate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium hydrogen sulfate monohydrate], C₅H₅N₄O₂⁺·HSO₄⁻·H₂O, (II), the xanthine molecules are protonated at the imine N atom with the transfer of an H atom from the inorganic acid. The asymmetric unit of (I) contains a xanthinium cation, a nitrate anion and one water molecule, while that of (II) contains two crystallographically independent xanthinium cations, two hydrogen sulfate anions and two water molecules. A pseudo‐quadruple hydrogen‐bonding motif is formed between the xanthinium cations and the water molecules via N—H...O and O—H...O hydrogen bonds in both structures, and leads to the formation of one‐dimensional polymeric tapes. These cation–water tapes are further connected by the respective anions and aggregate into two‐dimensional hydrogen‐bonded sheets in (I) and three‐dimensional arrangements in (II).     

4,6‐Diaminopyrimidine‐2(1H)‐thione hemihydrate: a three‐dimensional hydrogen‐bonded framework

In the title compound, C₄H₆N₄S·0.5H₂O, there are two independent pyrimidinethione units, both of which lie across mirror planes in the space group Cmca. Hence, the H atoms bonded to the ring N atoms in each molecule are disordered over two symmetry‐related sites, each having an occupancy of 0.5. The water molecule lies across a twofold rotation axis parallel to [010]. The molecular components of (I) are linked by seven independent hydrogen bonds, of N—H...N, N—H...S, N—H...O and O—H...S types. A combination of disordered N—H...N hydrogen bonds and ordered N—H...S hydrogen bonds links the pyrimidinethione units into a continuous tubular structure. The water molecule acts as both a double donor of hydrogen bonds and a double acceptor, forming hydrogen bonds with components of four distinct pyrimidinethione tubes, thus linking these tubes into a three‐dimensional structure.     

Proton‐transfer and non‐transfer in compounds of quinoline and quinaldic acid with l‐tartaric acid

The structures of two compounds of l ‐tartaric acid with quinoline, viz. the proton‐transfer compound quinolinium hydrogen (2R,3R)‐tartrate monohydrate, C₉H₈N⁺·C₄H₅O₆⁻·H₂O, (I), and the anhydrous non‐proton‐transfer adduct with quinaldic acid, bis­(quinolinium‐2‐carboxyl­ate) (2R,3R)‐tar­taric acid, 2C₁₀H₇NO₂·C₄H₆O₆, (II), have been determined at 130 K. Compound (I) has a three‐dimensional honeycomb substructure formed from head‐to‐tail hydrogen‐bonded hydrogen tartrate anions and water mol­ecules. The stacks of π‐bonded quinolinium cations are accommodated within the channels and are hydrogen bonded to it peripherally. Compound (II) has a two‐dimensional network structure based on pseudo‐centrosymmetric head‐to‐tail hydrogen‐bonded cyclic dimers comprising zwitterionic quinaldic acid species which are inter­linked by tartaric acid mol­ecules.     

Mono­alkyl­ated 4′‐aryl‐substituted terpyridines

1‐Methyl‐2‐[4‐phenyl‐6‐(pyridinium‐2‐yl)­pyridin‐2‐yl]­pyridinium diperchlorate, C₂₂H₁₉N₃²⁺·2ClO₄⁻, (I), and 2‐[4‐(methoxy­phenyl)‐2,2′‐bipyridin‐6‐yl]‐1‐methyl­pyridinium iodide, C₂₃H₂₀N₃O⁺·I⁻, (II), both crystallize in the monoclinic space group P2₁/c. In contrast with the monocharged mol­ecule of (II), the doubly charged mol­ecule of (I) contains an additional protonated pyridine ring. One of the two perchlorate counter‐anions of (I) interacts with the cation of (I) via an N—H⋯O hydrogen bond. In (II), two mol­ecules related by a centre of symmetry are connected by weak π–π interactions, forming dimers in the crystal structure.     

2‐[(E)‐(4‐Chloro­phenyl)­methyl­ene­amino]‐N‐(X‐methyl­phenyl)‐4,5,6,7‐tetra­hydro‐1‐benzo­thio­phene‐3‐carbox­amide,where X = 2 and 3

The title compounds, both C₂₃H₂₁ClN₂OS, are isomeric, with (I) and (II) being the N‐3‐methyl­phenyl and N‐2‐methyl­phenyl derivatives, respectively. The dihedral angle between the 4‐chloro­phenyl group and the thio­phene ring in (II) [38.1 (1)°] is larger than that in (I) [7.1 (1)°], indicating steric repulsion between the chloro­phenyl and o‐toluidine groups in (II). In both compounds, an intramolecular N—H⋯N hydrogen bond forms a pseudo‐six‐membered ring, thus locking the molecular conformation. In the crystal structures, mol­ecules are connected via N—H⋯O hydrogen bonds, forming chains along the b axis in (I) and along the c axis in (II). Intermolecular C—H⋯O/S and π–π interactions are also observed in (II), but not in (I).     

A dihydro‐β‐agarofuran sesquiterpene from Maytenus boaria

The natural compound (1S ,4S ,5S ,6R ,7R ,8R ,9R ,10S )‐6‐acetoxy‐4,9,10‐trihydroxy‐2,2,5a,9‐tetramethyloctahydro‐2H‐3,9a‐methanobenzo[b ]oxepin‐5‐yl furan‐3‐carboxylate, C₂₂H₃₀O₉, (I), is a β‐agarofuran sesquiterpene isolated from the seeds of Maytenus boaria as part of a study of the secondary metabolites from Chilean flora. The compound presents a central structure formed by a decalin system esterified with acetate at site 1 and furan‐3‐carboxylate at site 9. The chirality of the skeleton can be described as 1S ,4S ,5S ,6R ,7R ,8R ,9R ,10S , which is consistent with that suggested by NMR studies. Unlike previously reported structures of sesquiterpenes containing a pure dihydro‐β‐agarofuran skeleton, (I) exhibits a three‐dimensional hydrogen‐bonded network.     

(±)‐6‐tert‐Butyl‐8‐hydroxymethyl‐2‐­phenyl‐4H‐1,3‐benzodioxin and 2,2,2′,2′,6,6′‐hexamethyl‐8,8′‐methylenebis(4H‐1,3‐benzodioxin)

Two compounds containing 1,3‐benzodioxin groups are reported, namely (±)‐6‐tert‐butyl‐8‐hydroxy­methyl‐2‐phenyl‐4H‐1,3‐benzodioxin, C₁₉H₂₂O₃, (I), and 2,2,2′,2′,6,6′‐hexamethyl‐8,8′‐methyl­enebis(4H‐1,3‐benzodioxin), C₂₃H₂₈O₄, (II).The hydroxy groups of neighbouring mol­ecules in (I) are hydrogen bonded to each other, giving rise to double‐row chains. The mol­ecule in (II) adopts a `butterfly' conformation, with the O atoms in distal positions. In both compounds, the dioxin rings are in distorted half‐chair conformations.