Synthesis, Structure, and Properties of Corona[6]arenes and Their

Article Cite This: J. Org. Chem. 2018, 83, 1502−1509

pubs.acs.org/joc

Synthesis, Structure, and Properties of Corona[6]arenes and Their Assembly with Anions in the Crystalline State Meng-Yao Zhao,† De-Xian Wang,*,‡ and Mei-Xiang Wang*,† †

MOE Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, China ‡ CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science, Beijing National Laboratory for Molecular Sciences, Beijing 100191, China S Supporting Information *

ABSTRACT: The synthesis, conformational structure, electronic property, and anion complexation of novel coronarenes were systematically studied. A number of corona[4]arene[2]tetrazines that contain different combinations of nitrogen atoms with O, S, SO2, and CH2 as bridging units were synthesized conveniently by means of a fragment coupling strategy based on efficient nucleophilic aromatic substitution reaction of easily available aromatic dinucleophiles and 3,6-dichlorotetrazine. The resulting macrocycles adopt crownlike conformational structures with the nitrogen bridge(s) forming conjugation with carbonyl and the other heteroatom linkages with tetrazine. CV and DPV measurements showed that the tetrazine-bearing coronarenes were electron deficient with reduction potentials ranging from −896 to −960 mV. Owing mainly to noncovalent anion−π attractive interactions, N2,O4-corona[4]arene[2]tetrazine formed complexes with anions of varied geometries and shapes yielding diverse assembled structures in the solid state.

■

INTRODUCTION Design and construction of novel and functional macrocyclic molecules have always been one of the most attractive research areas in supramolecular science.1 Tailor-made synthetic macrocycles offer, for instance, excellent model systems to study the nature of various noncovalent interactions. Functional macrocycles, on the other hand, provide essential building blocks for the fabrication of sophisticated (supra)molecular structures, advanced materials, and machinery systems. Moreover, engineered two- and three-dimensional macrocycles with well-defined cavities are unique molecular tools in highly selective synthesis and in the study of reaction mechanism elucidation. For more than a decade, we2,3 and other groups4−7 have been exploring the macrocyclic and supramolecular chemistry of heteracalixaromatics. The easy availability, tunable conformational structure, and V-shaped cavity size and electronic property render heteracalixaromatics powerful and versatile host molecules in the study of molecular recognition and selfassembly.8 To seek host molecules that contain the cylinder cavity, we have recently devised a new type of synthetic macrocycles, namely, coronarenes,9 by means of chemical bond recombination of heteracalixaromatics. The covalent alignment of different p-(het)arylene and heteroatoms in a cyclic fashion would result in a nearly limitless amount of diverse coronarenes. More fascinatingly, the interplay between various heteroatom and (hetero)aromatic ring components through the © 2018 American Chemical Society

stereoelectronic effect would generate cylindroid cavities with finely regulatable sizes and controllable electronic features. We have established efficient methods for the construction of coronarenes. For example, one-pot reaction of a few arene-1,4diols and -1,4-dithiols with 3,6-dichlorotetrazine produces a number of symmetric oxygen- and sulfur-bridged corona[3]arene[3]tetrazines, respectively.9−11 The fragment-coupling strategy, on the other hand, provides facile accesses to coronarenes bearing either giant macrocyclic rings or functional groups.12 Furthermore, post-macrocyclization manipulations13 including functional group modification,14 tetrazine transformation based on inverse electron demand Diels−Alder reaction,10,11 and selective oxidation of sulfur linkages10 afford sophisticated coronarene derivatives. Coronarenes have been shown to adopt crownlike conformational structures with varied cylinder cavities which are influenced dominantly by the nature of heteroatoms, viz. their polar and resonance effects.9,10 Most significantly, the assembly of different heteroatom linkages with electron-rich or -deficient (hetero)aromatic rings leads to coronarenes with contrasting electronic characteristics which are advantageous in recognition of fullerenes,11b,12 cations10,14,15 or anions,9 respectively. In contrast to a number of oxygen- and sulfur-bridged coronarenes in the literature, 9−17 there are very few Received: December 13, 2017 Published: January 12, 2018 1502

DOI: 10.1021/acs.joc.7b03136 J. Org. Chem. 2018, 83, 1502−1509

Article

The Journal of Organic Chemistry coronarenes which contain nitrogen atom as the linking units.18−21 Employing the Pd-catalyzed cross-coupling C−N bond forming protocol, the synthesis of N-(p-methoxyphenyl)N6-corona[6]arene was shown by Ito and Tanaka18 in 2010 and an analogous N-phenyl-N6-corona[6]arene by Yang and Su19 in 2012. Very recently, Jäkle reported the preparation of an interesting B3,N3-corona[6]arene macrocycle. It is worth noting that, attributable to the integrated triarylamine subunits, the resulting nitrogen-linked corona[6]arenes exhibit intriguing optoelectronic and electrochemical properties useful for organic electronics.21 To the best of our knowledge, however, coronarenes which are composed of both heteroaromatic rings and nitrogen atom linkages remain unknown. As a continuation of our research program aiming at the development of novel synthetic macrocycles and their applications in supramolecular chemistry, we undertook the current study, Reported herein are the convenient synthesis, conformational structure, and property of unprecedented corona[4]arene[2]tetrazines which contain nitrogen and other heteroatoms as the bridging units. We have found that all corona[4]arene[2]tetrazines synthesized are electron deficient and able to complex anions of different geometries and shapes by anion−π and hydrogen-bonding interactions, affording diverse assembled structures in solid state.

Table 1. Optimization for the Synthesis of N2,O4Corona[4]arene[2]tetrazine 4 from the Macrocyclic Condensation between 1a and 3

■

RESULTS AND DISCUSSION We have shown previously that the nucleophilic aromatic substitution reaction works excellently for the construction of heteracalixaromatics2,3 and coronarenes9−11,13,14 when appropriate aromatic dinucleophiles react with cyanuric acid chloride and 3,6-dichlorotetrazine, respectively. To synthesize diverse coronarenes and to study the effect of the combination of nitrogen with other heteroarom linkages on the structure and properties of the macrocycles, we focused the fragment coupling strategy based on efficient nucleophilic aromatic substitution reaction in all steps. To develop the general method, we examined initially the preparation of N2,O4corona[4]arene[2]tetrazine compound using N,N-bis(4hydroxyphenyl)acetamide 1a22 and 3,6-dichlorotetrazine 223 as building blocks. In the presence of triethylamine as an acid scavenger, two-directional nucleophilic aromatic substitution reactions of 1a with 3 equiv of 2 afforded a linear tetramer 3 in 74% yield (Scheme 1). The macrocyclization between 3 and 1a

entry

base

solvent

temp (°C)

conc (mM)

1 2 3 4 5 6 7 8 9 10 11

DIPEA DIPEA DIPEA DIPEA DIPEA DIPEA Et3N Na2CO3 Cs2CO3 DIPEA DIPEA

CH2Cl2 CHCl3 CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN CH3CN

reflux reflux 25 40 60 reflux 60 60 60 60 60

5 5 5 5 5 5 5 5 5 10 5

timea (h) 25 25 25 25 25 25 25 25 25 25 25

+ + + + + + + + + + +

5 5 5 5 5 5 5 5 5 5 60

yieldb (%) c c 59 58 73 68 70 d d 62 69

a

Time of addition plus time for further reaction. bIsolated yield. cA mixture of polar and inseparable oligomers was formed in addition to starting 1a. dCompound 3 underwent decomposition.

tetramer 3 is sparingly soluble in both chlorinated solvents, and a mixture of polar and inseparable oligomers was formed (entries 1 and 2, Table 1). Fortunately, acetonitrile turned out to be a good reaction medium, and the reaction proceeded very rapidly to give the desired macrocyclic product. Notably, the chemical yield of the product increased from around 60% to 73% when the reaction temperature was raised from 25 to 60 °C (entries 3−5, Table 1). Further increase of reaction temperature, however, did not improve the yield (entry 6, Table 1). The use of triethylamine instead of DIPEA resulted in a slight decrease of the chemical yield (entry 7, Table 1), while the use of inorganic base Na2CO3 had a detrimental effect on the macrocyclization (entry 8, Table 1). It is important to address that the initial concentration of reactants needed to be controlled around 5 mM. This has been exemplified by the erosion of chemical yield when the concentration of reactants was doubled due to most probably the more favorable oligomerization reaction pathway (entry 10, Table 1). Equally important is the control of reaction time. It seemed advantageous to quench the reaction right after the completion of the reaction since elongation of reaction time, which was unnecessary, caused slight decrease of chemical yield of 4 (entry 11, Table 1). Under the optimized conditions, new coronarenes that contain different combinations of bridging units were synthesized by reacting 3 with other aromatic diols and dithiols. The reaction took place rapidly, but the efficiency for the macrocyclization was strongly dependent upon the structure of the nucleophiles and, particularly, the linkage Y between phenylenes of 1b−h. For example, 4,4′-sulfonyldiphenol 1b reacted as efficiently as N,N-bis(4-hydroxyphenyl)acetamide 1a with 3, producing the corresponding N,O4,(SO2)-

Scheme 1. Preparation of Linear Tetramer 3 from the Reaction of 1a and 2

was surveyed in terms of variables such as solvent and temperature. Since oligomerization reaction is always in competition with macrocyclization in the synthesis, the reaction between 3 and 1a was conducted in a pseudodilute solution manner (see the Experimental Section). The results compiled in Table 1 indicated clearly that the dichloromethane and chloroform are not good solvents for the reaction because 1503


Article

The Journal of Organic Chemistry

and also to shed light on the conformation of macrocycles, high-quality single crystals of 4, 5, 7, 9, and 11 were obtained from recrystallization by diffusion of ethyl ether into their DMF (4), acetonitrile (5, 9, 11), or a mixed acetonitrile/DMSO solution (7) at room temperature and their molecular structures were determined by X-ray diffraction analysis. Structures illustrated in Figure 1 show that macrocycles adopt

corona[4]arene[2]tetrazine 5 in a high yield (entry 1, Table 2). When the sulfone group was replaced by sulfur, oxygen, and Table 2. Synthesis of Corona[4]arene[2]tetrazines 5−11 Containing Various Bridging Atoms from the Reaction of 3 with 1b−h

a

entry

1

2

3

4

5

6

7

1 X Y product % yielda

1b O SO2 5 73

1c O S 6 15

1d O O 7 15

1e O CH2 8 17

1f S S 9 40

1g S O 10 48

1h S CH2 11 46

Isolated yield.

methylene, diphenols 1c−e were also able to undergo the nucleophilic aromatic substitution reaction with 3. The desired target macrocycles 6−8 were obtained, however, in low yields (entries 2−4, Table 2). In these cases, oligomerization reaction seemed to exceed macrocyclization under the identical conditions, yielding a large amount of polar and inseparable oligomers. Remarkably, when 4,4′-thio- (1f), 4,4′-oxy- (1g), and 4,4′-methylenedibenzenethiols (1h) were applied, macrocyclization reaction proceeded effectively to yield coronarene products 9, 10, and 11, respectively, in good yields (entries 5− 7, Table 2). The aforementioned outcomes revealed a subtle effect of the combination of atom bridges on the conformation of linear hexamers prior to macrocyclization. It is worth addressing that the synthesis of highly symmetric N2O4-corona[4]arene[2]tetrazine 4 was not necessary executed by the stepwise fragment coupling method depicted in Scheme 1 and Table 1. Practically, a simple one-pot reaction of N,Nbis(4-hydroxyphenyl)acetamide 1a and equimolar 3,6-dichlorotetrazine 2 in the presence of DIPEA in acetonitrile at 70 °C furnished the formation of 4 in 52% yield (Scheme 2). The structure of all coronarene products 4−11 was supported by their spectroscopic and elemental analysis data (see the Experimental Section and the Supporting Information). To put the structures of products beyond any ambiguity,

Figure 1. X-ray molecular structure of coronarenes 4 (A), 5 (B), 7 (C), 9 (D), and 11 (D) with top (left) and side (left) views. Solvent molecules are omitted for clarity.

Scheme 2. Synthesis of 4 from a One-Pot Reaction of 1a and 2

generally the hexagon-like coronary conformation. The combinations of atom linkages played obviously a role in regulating the conformation of each individual coronarene. Six heteroatoms in N2O4-corona[4]arene[2]tetrazine 4, for example, adopt a seriously pinched chair form with four oxygen atoms being in the same plane, while in N,O4,(SO2)corona[4]arene[2]tetrazine 5 and N,O5-corona[4]arene[2]tetrazine 7, all bridging atoms locate almost on the same plane. It is evident that tetrazine rings are procumbent on the plane defined by heteroatoms whereas phenylene components tend to perpendicular to the plane. Introduction of sulfur atoms 1504


Article


transitions of a tetrazine component.23 In addition, for 4−8, another stronger absorption band (ε = 7.39 × 103 to 8.69 × 103 L·mol−1·cm−1) was observed at a short wavelength region λmax = 329−338 nm. Interestingly, this absorption band due to π→ π* transitions shifted bathochromically to λmax = 382−388 nm (ε = 3.13 × 103 to 3.27 × 103 L·mol−1·cm−1) when sulfur bridges were introduced into the macrocycles (Supporting Information). The redox properties of 4−11 were studied by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). As depicted in Figure 3, cyclic voltammo-

into macrocyclic skeleton led to the significant conformational change. This has been demonstrated clearly by the observation of slightly twisted crown-like conformations in which six linking atoms form a boat chair structure in 9 and 11. Despite the variation of conformations, only marginal difference was observed for macrocyclic cavity. The distance between two tetrazine centroids for instance was in a narrow range from 9.12 to 9.62 Å. It is also noteworthy that the interatomic distance of bridging nitrogen to the carbon of phenylenes and to that of carbonyl are some 1.44 and 1.37 Å, respectively, in all structures, suggesting the delocalization of nitrogen lone-pair electrons into the carbonyl rather than into the phenylenes. Finally, judging on the bond lengths and angles, heteroatoms in between tetrazine and benzene tend to form conjugation with tetrazine moiety due to most likely the electron-deficient nature of heteroaromatic ring. The propensity of heteroatoms to form different degrees of conjugation with tetrazine rings would result in the regulation of electron density of the macrocycles, which we will discuss later on. In contrast to coronarenes which contain only oxygen and sulfur atoms as linkages, the newly acquired macrocyclic products 4−11 gave two sets of proton and carbon signals in their 1H and 13C NMR spectra, respectively, at room temperature (Figure 2 and Supporting Information). When

Figure 3. Cyclic voltamograms and differential pulse voltamograms of macrocycles 4−11 (1 mM) at 293 K. CV (scan rate 100 mVs−1) and DPV (scan rate 10 mVs−1) measurements were carried out in argonpurged CH3CN with [n-Bu4N][PF6] (0.1 M) as the supporting electrolyte. Potentials were recorded vs Fc+/ Fc.

grams of 4−8 gave nearly the identical electrochemical response showing a characteristic reversible redox couple due to one electron reduction and oxidation of the tetrazine moiety.24 The half-wave reduction potentials measured by DPV, which are same to that obtained by CV measurement, are in the range of −896 to −960 mV versus Fc+/Fc. Interestingly, evidenced by both CV and DPV results in Figure 3, the sulfide linkage-containing corona[5]arenes 9−11 proceeded reversibly through a sequential one-electron redox process, indicating the occurrence of electronic communication between the two identical tetrazine redox centers within the macrocycles. The potentials for the first redox measured by CV and DPV ranged from −921 to −958 mV versus Fc+/Fc. It is important to emphasize that the redox properties of coronarenes 4−11 were strongly dictated by the nature of the heteroatom linkages and their combination alike. The coronarene 5, which contains one sulfone unit, appeared most electron deficient whereas the methylene-linked analog 8 was least electron deficient. The different redox property stemmed obviously from the interplay of heteroatoms with aromatic rings. In other word, incorporation of varied combinations of heteroatoms into nitrogenbearing corona[4]arene[2]tetrazines enabled the construction of synthetic macrocycles with tunable electronic features. The past decade has witnessed the tremendous progress in the study of noncovalent anion−π interactions.24,25 A growing number of experimental evidence26 and plethora of theoretical calculations27 substantiate the importance of anion−π inter-

Figure 2. Partial variable-temperature 1H NMR spectra of 4 in DMSO-d6.

the temperature of NMR probe was increased to above 100 °C, both proton and carbon resonance signals emerged into one single set of sharp and well-resolved peaks (Figure 2). The variable-temperature NMR spectra indicated the presence of two stable conformers at ambient temperature. They were able to undergo very fast interconversion at a high temperature in relative to the NMR time scale. The observation of two sets of resonance signals and of high coalescence temperatures was most probably due to the presence of amide substructure within the macrocyclic scaffold. In accordance with the structures revealed by X-ray crystallography (vide supra), the conjugation of nitrogen lone pair electrons with carbonyl would rigidify the structure decreasing macrocyclic mobility. To shed light on the physicochemical properties of resulting coronarenes 4−11, we investigated their electronic spectra and redox properties. The UV/visible spectra of all 4−11 in acetonitrile exhibited one absorption band at λmax = 517−522 nm with molar extinction coefficients (ε) being around 1.72 × 103 to 2.00 × 103 L·mol−1·cm−1. This is characteristic of n→π* 1505


Article

The Journal of Organic Chemistry actions as the driving force in assembled chemical and biological systems. The coronarenes with varied conformations, cavities, and electronic properties would provide unique macrocyclic hosts in study of supramolecular science. The electron-deficient nature of tetrazine-bearing coronarenes prompted us to explore macrocycles 4−11 as electron-neutral receptors for anion complexation. The interactions of coronarene 4 with anions was surveyed using electron-spray ionization mass spectrometry. To reveal the structure effect, anions of different geometries and shapes such as spherical chloride, bromide, and iodide, linear cyanide, thiocyanate and azides, planar triangular nitrate and carbonate, tetrahedral tetrafluoroborate, and octahedral hexafluorophophate were selected. In almost all cases, the mixed sample of macrocycle 4 with tetraalkylammonium salts in acetonitrile displayed intense mass peaks corresponding to [anion·4]− (Supporting Information), implying the formation of the 1:1 anion−host complexes in gaseous phase under mass conditions. Since no appreciable changes in UV−vis, fluorescence, or NMR spectra of tetrazine moieties were observed when macrocycle 4 was titrated with anions due to most likely low sensitivity or binding in solution, we focused on the complexation of coronarene 4 with anions in the solid state. To our delight, macrocycle 4 was able to cocrystallize with tetraalkylammonium salts of bromide, iodide, thiocyanate, nitrate, tetrafluoroborate, perchlorate, and even naphthalene-1,5-disulfonate, yielding X-ray quality single crystals. Molecular structures of the host−guest complexes, which were determined unambiguously by X-ray diffraction analysis, are depicted in Figures 4−6. On the basis of the crystallographic results, all complexes involved typical anion−π interactions between anion and tetrazine moiety with only the exception of complexation of 4 with tetraalkylammonium nitrate in which anion interacted with tetrazine through σ-type interactions (Figure S13 in Supporting Information). The anions do not intrude into the cavity to be complexed by two tetrazine moieties within one macrocyclic molecule. Instead, most of the anions were sandwiched by two tetrazine rings from two macrocycles. Depending on the nature of anions, and due to the effect of different noncovalent bond interactions between anions and coronarenes, varied supramolecular assemblies were generated in the crystalline state. It should be addressed that cations in all complexes do not interact with electron-deficient tetrazine rings though they have short contact to anions. Some important structure features are noted below. As shown in Figure 4, the bromide anion (Br1) in [4·Br−] complex locates over the center of the tetrazine (T1) ring. The short distance (dBr1‑plane = 3.464 Å) between Br1 to the plane of tetrazine (T1) indicates the formation of typical anion-π interaction. Noticeably, the tetrazine ring in complexation with bromide adopts a pinched boat conformation with the dihedral angle of planeN−N−N−N and planeC−N−N being 16.2°. The deformation of a planar aromatic ring to a flattened boat conformation also accords the typical attractive anion−π interactions predicted by theoretical calculations.27d Besides, Br1 also has a short contact (dBr1‑plane = 3.357 Å) to tetrazine (T2) ring from the neighboring coroanarene. The bromide anion (Br1) is sandwiched by two tetrazine (T1 and T2) rings due to dual anion−π interactions. Probably because of the steric hindrance coming from the macrocyclic backbone, these two tetrazine rings are not face-to-face paralleled. Instead, they open up slightly to give a V-shaped alignment, with the nearest and

Figure 4. X-ray molecular structures of complexes between coronarene 4 and n-Bu4NBr (A), n-Bu4NI (B), n-Bu4NSCN (C), and n-Bu4NClO4 (D). Cations and solvent molecules are omitted for clarity.

longest distances of T1 and T2 being 5.999 (dC2−C18) and 7.080 Å (dC1−C17), respectively (Figure 4, left column). It is evident 1506


Article

The Journal of Organic Chemistry that, directed by dual anion−π interactions, bromide anions act as a gluing component to assemble corona[4]arene[2]tetrazines into one-dimensional structure (Figure 4, right column). Despite of varied geometries, anions including I−, SCN−, and ClO4− form analogous anion-π complexes with the tetrazines embedded in corona[4]arene[2]tetrazine and yield similar assembled supramolecular structures. However, degree of deformation of tetrazine ring from planarity varied depending on the nature of anions. The dihedral angle of boat conformation of complexing tetrazine increased for instance in the order of ClO4− (10.62°), SCN− (11.92°), I− (12.18°), and Br− (16.02°). The shortest and longest distances between two tetrazines T1 and T2 are 5.999 and 7.080 Å (Br−), 6.270 and 7.173 Å (I−), 6.531 and 8.007 Å (SCN−), and 6.648 and 8.093 Å (ClO4−), respectively (Figure 4, left column). The order of dihedral angles and intertetrazine distances correlate nicely with the order of ionic radius of the anions (0.196 Å for Br− < 0.220 Å for I− < 0.213 Å for CNS− < 0.240 Å for ClO4−), indicating the close association of anions to two tetrazine rings. Finally, owing to the orientation of neighboring coronarenes, one-dimensional pseudohelical assembled structures were observed in the solid state (Figure 4, right column). Being different from the aforementioned anion−π complexes in which anions are sandwiched by two electron-deficient tetrazine rings, complex [4·BF4−] shows another supramolecular motif in the structure illustrated in Figure 5. While

Figure 6. X-ray molecular structure of complex between coronarene 4 and tetrabutylammonium naphthalene-1,5-disulfonate. Cation and solvent molecules are omitted for clarity.

solvent molecules which associate with the other tetrazine ring of coronarene via a lone-pair electron−π interaction28 (Figure 6).

■

CONCLUSION In summary, we have synthesized a number of corona[4]arene[2]tetrazines which contain varied combinations of nitrogen, oxygen, sulfur, sulfone, and methylene linkages by means of a fragment-coupling strategy based on nucleophilic aromatic substitution reaction. We have also demonstrated that the interplay between heteroatoms and aromatic units play a role in regulating the conformational structures, and more importantly the electronic properties of the resulting macrocycles. The electron-deficient nature of tetrazine engendered the synthesized coronarenes unique building blocks to form diverse complexes with anions of different geometries and shapes driven mainly by attractive anion−π interactions.

■

EXPERIMENTAL SECTION

All commercially available reagents were used as received. TLC analysis was performed on precoated, glass-backed silica gel plates and visualized under UV light. Flash column chromatography was performed on silica gel (200−300). Anhydrous solvents were dried by 4 Å molecular sieves. 1H and 13C NMR spectra were recorded using 400 MHz spectrometers. Chemical shifts are reported in ppm versus tetramethylsilane with either tetramethylsilane or the residual solvent resonance used as an internal standard. Abbreviations are used in the description of NMR data as follows: chemical shift (δ, ppm), multiplicity (s = singlet, d = doublet, t = triplet, m = multiplet), coupling constant (J, Hz). Infrared spectra were recorded using a FTIR spectrometer with KBr discs in the 4000−400 cm−1 region. UV−vis spectra were recorded using a UV−vis spectrophotometer. Mass and elemental analyses were performed at the Institute of Chemistry, CAS. Melting points are uncorrected. Synthesis of Compound 3. To a solution of 3,6-dichlorotetrazine 2 (3 mmol) in anhydrous acetonitrile (10 mL) at 0 °C was added dropwise a solution of 1a (1 mmol) and Et3N (3 mmol) in acetonitrile (5 mL) during 25 min. The resulting mixture was allowed to stir for another 5 min at 0 °C. The mixture was quenched by addition of brine (30 mL), and the mixture was extracted with ethyl acetate (3 × 20 mL). The combined organic phase was washed with brine (3 × 50 mL) and dried over anhydrous Na2SO4. After filtration and removal of solvent, the residue was chromatographed on a silica gel column with a mixture of DCM and acetone as the mobile phase (5:1) to give pure product 3 (349 mg, 74% yield) as a red solid: mp 236−238 °C; 1H NMR (400 MHz, DMSO-d6, 60 °C) δH 7.58 (d, J = 8.2 Hz, 4H), 7.47 (d, J = 8.7 Hz, 4H), 2.02 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 60

Figure 5. X-ray molecular structure of complex between coronarene 4 and n-Et4NBF4. Cation and solvent molecules are omitted for clarity.

BF4− forms typical anion−π interaction with one tetrazine ring, as evidenced by the distance of one fluorine atom of BF4− to tetrazine plane (dF‑plane = 2.731 Å), BF4− interacts with the second coronarene by forming multiple hydrogen bonds. The multiple anion-π and hydrogen bonding interactions consequently lead to the formation of an interesting ladder-like self-assembly (Figure 5). In the case of complex between coronarene 4 with naphthalene-1,5-disulfonate, an organic bis-anionic species, each sulfonate group complexes with one tetrazine ring due to the typical anion−π interactions (Figure 6). As a consequence, one naphthalene-1,5-disulfonate appears to be encapsulated by two coronarene molecules. Each complexed capsule then assembles into a linear structure through DMSO 1507


Article

The Journal of Organic Chemistry °C) δC 169.2, 167.0, 163.8, 150.2, 141.0, 129.2, 121.4, 23.1; IR (KBr, cm−1) ν 1674, 1505, 1443, 1371, 1303, 1180, 1160; HRMS (APCI orbitrap) calcd for C18H12Cl2N9O3+ [M + H]+ 472.0435, found 472.0417. Anal. Calcd for C18H11Cl2N9O3: C, 45.78; H, 2.35; N, 26.69. Found: C, 45.41; H, 2.29; N, 27.00. General Procedure for the Synthesis of 4−11. To a solution of DIPEA (1.1 mmol) in acetonitrile (90 mL) at 60 °C was added dropwise a solution of 3 (0.5 mmol) and 1a−h (0.5 mmol) in acetonitrile (10 mL) during 25 min. The resulting mixture was kept allowed to stir for another 5 min under 60 °C. The reaction was then quenched by brine (100 mL) at room temperature, and the mixture was extracted with ethyl acetate (3 × 50 mL). The combined organic phase was washed with brine (3 × 100 mL) and dried over anhydrous Na2SO4. After filtration and removal of solvent, the residue was chromatographed on a silica gel column with a mixture of DCM and acetone or a mixture of petroleum ether (60−90 °C) and acetone as the mobile phase to give pure products 4−11. Characterization data of all products are listed below. 4 (mobile phase, DCM/acetone = 5:1) (234 mg, 73% yield): red solid, mp >300 °C; 1H NMR (400 MHz, DMSO-d6, 110 °C) δH 7.50 (d, J = 8.2 Hz, 8H), 7.32 (d, J = 8.7 Hz, 8H), 2.02 (s, 6H); 13C NMR (100 MHz, DMSO-d6, 130 °C) δC 168.4, 166.6, 150.6, 140.9, 129.1, 121.6, 21.9; IR (KBr, cm−1) ν 1664, 1505, 1473, 1389, 1332, 1207, 1190, 1114; HRMS (APCI - orbitrap) calcd for C32H23N10O6+ [M + H]+ 643.1797, found 643.1794. Anal. Calcd for C32H22N10O6· 0.5CH3COCH3: C, 59.91; H, 3.75; N, 20.86. Found: C, 59.75; H, 3.54; N, 20.57. A high-quality single crystal for X-ray diffraction analysis was obtained by diffusing ethyl ether vapor into the solution of 4 in DMF. 5 (mobile phase, DCM/acetone = 5:1) (237 mg, 73% yield): red solid, mp >300 °C; 1H NMR (400 MHz, DMSO-d6, 120 °C) δH 8.09 (d, J = 8.0 Hz, 4H), 7.55 (d, J = 8.0 Hz, 4H), 7.51 (d, J = 8.8 Hz, 4H),7.32 (d, J = 8.4 Hz, 4H), 2.02 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 120 °C) δC 168.5. 166.7, 166.2, 156.6, 150.5, 141.0, 138.7, 129.2, 122.1, 121.6, 22.0; IR (KBr, cm−1) ν 1668, 1588, 1504, 1474, 1383, 1333, 1206, 1154, 1104; HRMS (ESI - orbitrap) calcd for C30H20N9O7S+ [M + H]+ 650.1201, found 650.1188. A high-quality single crystal for X-ray diffraction analysis was obtained by diffusing ethyl ether vapor into the solution of 5 in acetonitrile. 6 (mobile phase, petroleum ether/acetone = 5:1−2:1) (46 mg, 15% yield): red solid, mp 282 °C dec; 1H NMR (400 MHz, DMSO-d6, 110 °C) δH 7.59 (d, J = 8.2 Hz, 4H), 7.51 (d, J = 8.2 Hz, 4H), 7.35 (d, J = 8.8 Hz, 4H), 7.31 (d, J = 8.8 Hz, 4H), 2.03 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 110 °C) δC 168.5, 166.6, 166.3, 152.0, 150.6, 141.0, 134.0, 132.9, 129.2, 121.6, 121.3, 22.2; IR (KBr, cm−1) ν 1682, 1504, 1475, 1386, 1330, 1200; HRMS (APCI - orbitrap) calcd for C30H20N9O5S+ [M + H]+ 618.1303, found 618.1298. Anal. Calcd for C30H19N9O5S·0.5H2O: C, 57.50; H, 3.22; N, 20.12. Found: C, 57.39; H, 3.34; N,19.86. 7 (mobile phase, DCM/acetone = 10:1) (45 mg, 15% yield): red solid, mp >300 °C; 1H NMR (400 MHz, DMSO-d6, 110 °C) δH 7.49 (d, J = 7.6 Hz, 4H), 7.34 (d, J = 8.0 Hz, 4H), 7.30 (d, J = 8.8 Hz, 4H), 7.19 (d, J = 8.8 Hz, 4H), 2.02 (s, 3H); 13C NMR (100 MHz, DMSOd6, 110 °C) δC 168.6, 166.8, 166.6, 156.2, 150.8, 148.4, 140.9, 129.1, 121.8, 121.7, 121.5, 22.2; IR (KBr, cm−1) ν 1666, 1504, 1473, 1387, 1330, 1185; HRMS (APCI - orbitrap) calcd for C30H20N9O6+ [M + H]+ 602.1531, found 602.1494. Anal. Calcd for C30H19N9O6·0.5H2O: C, 59.02; H, 3.30; N, 20.65. Found: C, 58.70; H, 3.16; N, 20.62. A high-quality single crystal for X-ray diffraction analysis was obtained by diffusing ethyl ether vapor into the solution of 7 in a mixture of acetonitrile and DMSO (v: v = 1:2). 8 (mobile phase, petroleum ether/acetone = 5:1−2:1) (51 mg, 17% yield): red solid, mp >300 °C; 1H NMR (400 MHz, DMSO-d6, 120 °C) δH 7.50 (d, J = 8.2 Hz, 4H), 7.40 (d, J = 8.7 Hz, 4H), 7.32 (d, J = 8.7 Hz, 4H), 7.18 (d, J = 8.2 Hz, 4H), 3.96 (s, 2H), 2.03 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 110 °C) δC 168.5, 166.7, 166.5, 150.6, 150.3, 140.9, 139.4, 129.3, 129.2, 121.6, 120.5, 22.1; IR (KBr, cm−1) ν 1667, 1505, 1473, 1390, 1331, 1197; HRMS (APCI - orbitrap) calcd for C31H22N9O5+ [M + H]+ 600.1738, found 600.1729. Anal. Calcd for

C31H21N9O5: C,62.10; H, 3.53; N, 21.03. Found: C, 62.33; H, 3.72; N, 19.99. 9 (mobile phase, petroleum ether/acetone = 5:1−2:1) (130 mg, 40% yield): red solid, mp 281 °C dec; 1H NMR (400 MHz, DMSO-d6, 110 °C) δH 7.68 (d, J = 8.2 Hz, 4H), 7.53(d, J = 8.4 Hz, 4H), 7.50 (d, J = 8.8 Hz, 4H), 7.39 (d, J = 8.7 Hz, 4H), 2.01 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 20 °C) δC 170.9, 169.4, 166.9, 151.1, 150.0, 141.4, 140.9, 136.1, 135.8, 134.3, 132.6, 132.2, 130.4, 129.2, 126.8, 126.7, 122.4, 121.6, 23.0; IR (KBr, cm−1) ν 1667, 1504, 1446, 1354, 1210, 1172, 1158; HRMS (APCI - orbitrap) calcd for C30H20N9O3S3+ [M + H]+ 650.0846, found 650.0833. Anal. Calcd for C30H19N9O3S3: C, 55.46; H, 2.95; N, 19.40. Found: C, 55.38; H, 3.18; N, 19.02. A highquality single crystal for X-ray diffraction analysis was obtained by diffusing ethyl ether vapor into the solution of 9 in acetonitrile. 10 (mobile phase, petroleum ether/acetone = 5:1−2:1) (152 mg, 48% yield): red solid, mp 272 °C dec; 1H NMR (400 MHz, DMSO-d6, 110 °C) δH 7.69 (d, J = 8.7 Hz, 4H), 7.52 (d, J = 8.2 Hz, 4H), 7.39 (d, J = 8.7 Hz, 4H), 7.17 (d, J = 8.7 Hz, 4H), 2.00 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 120 °C) δC 171.3, 168.8, 166.5, 157.8, 140.8, 135.5, 129.2, 121.6, 121.2, 120.5, 22.4; IR (KBr, cm−1) ν 1677, 1579, 1504, 1483, 1450, 1358, 1236, 1173, 1158; HRMS (APCI - orbitrap) calcd for C30H20N9O4S2+ [M + H]+ 634.1074, found 634.1063. Anal. Calcd for C30H19N9O4S2: C,56.86; H, 3.02; N, 19.89. Found: C, 57.14; H, 3.17; N, 19.65. 11 (mobile phase, petroleum ether/acetone = 5:1−2:1) (145 mg, 46% yield): red solid, mp 287 °C dec; 1H NMR (400 MHz, CDCl3, 20 °C) δH 7.52 (d, J = 8.2 Hz, 4H), 7.36−7.31 (m, 6H), 7.29 (d, J = 8.7 Hz, 2H), 7.23 (d, J = 8.7 Hz, 2H), 7.17 (d, J = 8.7 Hz, 2H), 3.91 (s, 2H), 2.08 (s, 3H); 13C NMR (100 MHz, DMSO-d6, 120 °C) δC 171.5, 168.5, 166.3, 150.1, 142.2, 140.7, 134.1, 129.5, 129.0, 123.5, 121.4, 40.2, 22.1; IR (KBr, cm−1) ν 1668, 1504, 1438, 1355, 1210, 1173, 1158; HRMS (APCI - orbitrap) calcd for C31H22N9O3S2+ [M + H]+ 632.1282, found 632.1266. Anal. Calcd for C31H21N9O3S2: C,58.94; H, 3.35; N, 19.96. Found: C, 59.16; H, 3.43; N, 19.63. A high-quality single crystal for X-ray diffraction analysis was obtained by diffusing ethyl ether vapor into the solution of 11 in acetonitrile. Synthesis of 4 from a One-Pot Reaction of 1a and 2. To a solution of DIPEA (2.2 mmol) in acetonitrile (180 mL) at 70 °C was added dropwise a solution of 1a (1 mmol) and 3,6-dichlorotetrazine 2 (1 mmol) in acetonitrile (20 mL) during 25 min. The resulting mixture was allowed to stir for another 5 min at 70 °C. The mixture was cooled to room temperature, and brine (200 mL) was added. The resulting mixture was extracted with ethyl acetate (3 × 100 mL). The combined organic phase was washed with brine (3 × 200 mL) and dried over anhydrous Na2SO4. After filtration and removal of solvent, the residue was chromatographed on a silica gel column with a mixture of DCM and acetone as the mobile phase to give pure product 4 (167 mg, 52% yield). Procedure for the Preparation of Single Crystals of the Complexes between 4 and Tetraalkylammonium Salts. A mixture of host 4 (6 mg) and 2 equiv of tetraalkylammonium salt, namely, n-Bu4NBr (7 mg), n-Bu4NI (6 mg), n-Bu4NSCN (6 mg), nBu4NNO3 (6 mg), Et4NBF4 (4 mg), n-Bu4NClO4 (7 mg), or tetrabutylammonium naphthalene-1,5-disulfonate (15 mg), were dissolved in a mixture of acetonitrile and DMSO (v/v = 1:2, 1.5 mL). Slow diffusion of diethyl ether vapor into the sample solution at ambient temperature afforded red single crystals of the corresponding complexes except for complex n-Bu4NI·4, which was purple.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b03136. X-ray data for coronarene 4 (CIF) X-ray data for coronarene 5 (CIF) X-ray data for coronarene 7 (CIF) X-ray data for coronarene 9 (CIF) X-ray data for coronarene 11 (CIF) 1508


Article


■

(13) Wu, Z.-C.; Guo, G.-H.; Wang, M.-X. Angew. Chem., Int. Ed. 2017, 56, 7151. (14) Guo, Q.-H.; Zhao, L.; Wang, M.-X. Angew. Chem., Int. Ed. 2015, 54, 8386. (15) Zhao, M.-Y.; Guo, Q.-H.; Wang, M.-X. Org. Chem. Front. 2017, DOI: 10.1039/C7QO00900C. (16) (a) Franke, J.; Vögtle, F. Tetrahedron Lett. 1984, 25, 3445. (b) Takeuchi, D.; Asano, I.; Osakada, K. J. Org. Chem. 2006, 71, 8614. (17) (a) Tsuchida, E.; Miyatake, K.; Yamamoto, K.; Hay, A. S. Macromolecules 1998, 31, 6469. (b) Zimmerman, D. A.; Koenig, J. L.; Ishida, H. Polymer 1996, 37, 3111. (c) Friederich, R.; Nieger, M.; Vögtle, F. Chem. Ber. 1993, 126, 1723. (d) Ben-Haida, A.; Colquhoun, H. M.; Hodge, P.; Raftery, J.; White, A. J. P.; Williams, D. J. Org. Biomol. Chem. 2009, 7, 5229 and references cited therein. (18) Ito, A.; Yokoyama, Y.; Aihara, R.; Fukui, K.; Eguchi, S.; Shizu, K.; Sato, T.; Tanaka, K. Angew. Chem., Int. Ed. 2010, 49, 8205. (19) Yang, T.-F.; Chiu, K. Y.; Cheng, H.-C.; Lee, Y. W.; Kuo, M. Y.; Su, Y. O. J. Org. Chem. 2012, 77, 8627. (20) Chen, P.; Lalancette, R. A.; Jäkle, F. Angew. Chem., Int. Ed. 2012, 51, 7994. (21) Ito, A. J. Mater. Chem. C 2016, 4, 4614. (22) Ohta, K.; Chiba, Y.; Ogawa, T.; Endo, Y. Bioorg. Med. Chem. Lett. 2008, 18, 5050. (23) Clavier, G.; Audebert, P. Chem. Rev. 2010, 110, 3299. (24) (a) Mascal, M.; Armstrong, A.; Bartberger, M. D. J. Am. Chem. Soc. 2002, 124, 6274. (b) Quinonero, D.; Garau, C.; Rotger, C.; Frontera, A.; Ballester, P.; Costa, A.; Deya, P. M. Angew. Chem., Int. Ed. 2002, 41, 3389. (c) Alkorta, I.; Rozas, I.; Elguero, J. J. Am. Chem. Soc. 2002, 124, 8593. (25) For reviews, see: (a) Hay, B. P.; Bryantsev, V. S. Chem. Commun. 2008, 2417. (b) Wang, D.-X.; Wang, M.-X. Chimia 2011, 65, 939. (c) Frontera, A.; Gamez, P.; Mascal, M.; Mooibroek, T. J.; Reedijk, J. Angew. Chem., Int. Ed. 2011, 50, 9564. (d) Chifotides, H. T.; Dunbar, K. R. Acc. Chem. Res. 2013, 46, 894. (e) Ballester, P. Acc. Chem. Res. 2013, 46, 874. (f) Vargas Jentzsch, A.; Hennig, A.; Mareda, J.; Matile, S. Acc. Chem. Res. 2013, 46, 2791. (g) Giese, M.; Albrecht, M.; Rissanen, K. Chem. Rev. 2015, 115, 8867 and references cited therein. (26) (a) Wang, D.-X.; Zheng, Q.-Y.; Wang, Q.-Q.; Wang, M.-X. Angew. Chem., Int. Ed. 2008, 47, 7485. (b) Wang, D.-X.; Wang, M.-X. J. Am. Chem. Soc. 2013, 135, 892. (c) Wang, D.-X.; Wang, Q.-Q.; Han, Y.; Wang, Y.; Huang, Z.-T.; Wang, M.-X. Chem. - Eur. J. 2010, 16, 13053. (d) Chifotides, H. T.; Schottel, B. L.; Dunbar, K. R. Angew. Chem., Int. Ed. 2010, 49, 7202. (e) Rosokha, Y. S.; Lindeman, S. V.; Rosokha, S. V.; Kochi, J. K. Angew. Chem., Int. Ed. 2004, 43, 4650. (f) Adriaenssens, L.; Gil-Ramírez, G.; Frontera, A.; Quiñonero, D.; Escudero-Adán, E. C.; Ballester, P. J. Am. Chem. Soc. 2014, 136, 3208. (27) (a) Xi, J.; Xu, X. Phys. Chem. Chem. Phys. 2016, 18, 6913 and references cited therein. (b) Zhang, J.; Zhou, B.; Sun, Z.-R.; Wang, X.B. Phys. Chem. Chem. Phys. 2015, 17, 3131. (c) Zheng, X.; Shuai, Z.; Wang, D. J. Phys. Chem. A 2013, 117, 3844. (d) Garau, C.; Quiñonero, D.; Frontera, A.; Costa, A.; Ballester, P.; Deyà, P. M. Chem. Phys. Lett. 2003, 370, 7. (28) (a) Gallivan, J. P.; Dougherty, D. A. Org. Lett. 1999, 1, 103. (b) Alkorta, I.; Rozas, I.; Elguero, J. J. Org. Chem. 1997, 62, 4687.

X-ray data for complex of 4 with n-Bu4NBr (CIF) X-ray data for complex of 4 with n-Bu4NI (CIF) X-ray data for complex of 4 with n-Bu4NSCN (CIF) X-ray data for complex of 4 with n-Bu4NNO3 (CIF) X-ray data for complex of 4 with n-Bu4NClO4 (CIF) X-ray data for complex of 4 with n-Bu4N-naphthalene1,5-disulfonate (CIF) X-ray data for complex of 4 with Et4NBF4 (CIF) 1 H and 13C NMR spectra of all products (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

De-Xian Wang: 0000-0002-9059-5022 Mei-Xiang Wang: 0000-0001-7112-0657 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank the National Natural Science Foundation of China (91427301, 21732004, 21421064) and Tsinghua University for financial support.

■

REFERENCES

(1) (a) Comprehensive Supramolecular Chemistry; Lehn, J.-M., Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Vögtle, F., Eds.; Pergamon: Oxford, 1996. (b) Calixarenes and Beyond; Neri, P., Sessler, J. L., Wang, M.-X, Eds.; Springer, 2016. (c) Liu, Z.; Nalluri, S. K. M.; Stoddart, J. F. Chem. Soc. Rev. 2017, 46, 2459. (d) Ogoshi, T.; Yamagishi, T.-a.; Nakamoto, Y. Chem. Rev. 2016, 116, 7937. (e) Shetty, D.; Khedkar, J. K.; Park, K. M.; Kim, K. Chem. Soc. Rev. 2015, 44, 8747. (2) (a) Wang, M.-X.; Zhang, X.-H.; Zheng, Q.-Y. Angew. Chem., Int. Ed. 2004, 43, 838. (b) Wang, M.-X.; Yang, H.-B. J. Am. Chem. Soc. 2004, 126, 15412. (3) Wang, M.-X. Acc. Chem. Res. 2012, 45, 182. (4) For a review of oxacalixaromatics, see: (a) Maes, W.; Dehaen, W. Chem. Soc. Rev. 2008, 37, 2393. (5) For a review of azacalixaromatics, see: Tsue, H.; Ishibashi, K.; Tamura, R. Top. Heterocycl. Chem. 2008, 17, 73. (6) For a review of thiacalixarenes, see: Morohashi, N.; Narumi, F.; Iki, N.; Hattori, T.; Miyano, S. Chem. Rev. 2006, 106, 5291. (7) See Chapters 14−16 and 18 in ref 1b. (8) For recent applications of heteracalixaromatics, see: (a) Fa, S.-X.; Chen, X.-F.; Yang, S.; Wang, D.-X.; Zhao, L.; Chen, E.-Q.; Wang, M.X. Chem. Commun. 2015, 51, 5112. (b) He, Q.; Ao, Y.-F.; Huang, Z.T.; Wang, D.-X. Angew. Chem., Int. Ed. 2015, 54, 11785. (c) Zhang, C.; Wang, Z.; Tan, L.; Zhai, T.-L.; Wang, S.; Tan, B.; Zheng, Y.-S.; Yang, X.-L.; Xu, H.-B. Angew. Chem., Int. Ed. 2015, 54, 9244. (d) Manganaro, N.; Lando, G.; Gargiulli, C.; Pisagatti, I.; Notti, A.; Pappalardo, S.; Parisi, M. F.; Gattuso, G. Chem. Commun. 2015, 51, 12657. (e) Zhang, H.; Yao, B.; Zhao, L.; Wang, D.-X.; Xu, B.-Q.; Wang, M.-X. J. Am. Chem. Soc. 2014, 136, 6326. (f) Zhang, Q.; Wang, M.-X. Org. Chem. Front. 2017, 4, 283. (i) Liang, D.-D.; Wang, M.-X. Org. Chem. Front. 2017, 4, 1425. (9) Guo, Q.-H.; Fu, Z.-D.; Zhao, L.; Wang, M.-X. Angew. Chem., Int. Ed. 2014, 53, 13548. (10) Guo, Q.-H.; Zhao, L.; Wang, M.-X. Chem. - Eur. J. 2016, 22, 6947. (11) (a) Fu, Z.-D.; Guo, Q.-H.; Zhang, L.; Wang, D.-X.; Wang, M.-X. Org. Lett. 2016, 18, 2668. (b) Lu, Y.; Fu, Z.-D.; Guo, G.-H.; Wang, M.X. Org. Lett. 2017, 19, 1590. (12) Ren, W.-S.; Zhao, L.; Wang, M.-X. Org. Lett. 2016, 18, 3126. 1509


Synthesis, Structure, and Properties of Corona[6]arenes and Their

Recommend Documents