Sustainable Catalytic Amination of Diols: From Cycloamination to

Nov 21, 2017 - N-Alkyl amines are extensively applied in the synthesis of functional materials, pharmaceuticals, and pesticides. The reaction of diols...
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Cite This: ACS Sustainable Chem. Eng. XXXX, XXX, XXX-XXX

Sustainable Catalytic Amination of Diols: From Cycloamination to Monoamination Yajuan Wu,†,‡ Hangkong Yuan,† and Feng Shi*,† †

State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, No.18, Tianshui Middle Road, Lanzhou 730000, China ‡ University of Chinese Academy of Sciences, No. 19A, Yuquan Road, Beijing 100049, China S Supporting Information *

ABSTRACT: N-Alkyl amines are extensively applied in the synthesis of functional materials, pharmaceuticals, and pesticides. The reaction of diols with amines is attractive and has been investigated for more than 30 years by using iridium, ruthenium, and other catalysts. However, the main products with diols as starting materials, especially for C4−C6 diols, are N-heterocyclic compounds because cyclization reaction is favorable in thermodynamics. Here, for the first time, a simple and non-noble catalyst CuNiAlOx prepared by a coprecipitation method was developed for the reaction of C4−C6 diols with amines to give monoamination products. This method offers an efficient and environmentally friendly method for the selective monoamination of diols. KEYWORDS: Diols, Amines, Monoamination, Non-noble metal catalyst

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INTRODUCTION Owing to its broad applications in many fields, such as pharmaceutical chemistry, pesticides and petrochemistry, the research on N-alkylation of amines has always been an important subject in catalysis.1,2 Traditionally, N-substituted amines are prepared by the alkylation of amines with halides. However, this method often suffers from serious environmental problems and expensive starting materials.3 Therefore, in many cases, N-substituted amines are synthesized by hydroamination4−6 and hydroaminomethylation7,8 reactions. Besides, an environmental benign procedure to produce N-substituted amines is the catalytic alkylation of amines with alcohols because alcohols are readily available, inexpensive, nontoxic, and water is the only byproduct theoretically.1,9−13 The reaction of diols with amines is attractive and has been widely investigated by using iridium,14−17 ruthenium10,18−22 and other23−26 catalysts. However, the main products with diols as starting materials, especially for C4−C6 diols, are Nheterocyclic compounds such as pyrrolidine, piperidine and azepane derivatives because cyclization reaction is favorable in thermodynamics. As it is well-known, alcohol-based amines of type RNH(CH2)nOH (R = alkyl, aryl) are widely used in pharmaceutical intermediates and functional materials. Thus, the controllable synthesis of monoaminated products by the reaction of amines and diols, especially C4−C6 diols, is very interesting both in academic and industrial fields. Herein, based on our continuing efforts in alcohol amination reactions,23,27−32 we propose a protocol to selectively synthesize N-(n-hydroxyalkyl)amines via monoamination of © XXXX American Chemical Society

diols with amines by using a simple CuNiAlOx heterogeneous catalyst through simple dynamic regulations (Scheme 1). Scheme 1. Catalytic Monoamination of Diols

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EXPERIMENTAL SECTION

Materials. All the chemicals were obtained commercially and used without further purification. Catalyst preparation. CuNiAlOx was prepared by the coprecipitation method. 1.44 g (5.96 mmol) of Cu(NO3)2·3H2O, 3.48 g (11.97 mmol) of Ni(NO3)2·6H2O, and 6 g (15.99 mmol) of Al(NO3)3·9H2O were added into 150 mL of deionized water at 80 °C in a 250 mL flask, and under vigorous stirring, 60 mL of Na2CO3 solution (1.415 mol) was added dropwise into the solution. The mixture was mechanically stirred for 5 h and then cooled to room temperature and filtrated. Following, the filtrate was washed with deionized water to neutral, dried at 100 °C for 5 h, calcined at 400 °C for 4 h, and then reduced under hydrogen flow at 450 °C for 2 h. Finally, the obtained catalyst was denoted as CuNiAlOx. The catalysts denoted as CuAlOx, NiAlOx, and CuNiOx were prepared with the same procedures. Received: September 21, 2017 Revised: October 29, 2017

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DOI: 10.1021/acssuschemeng.7b03373 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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ACS Sustainable Chemistry & Engineering Catalyst characterization. Mass spectra were in general recorded on an Agilent 5977A MSD GC-MS. High-resolution TEM analysis was carried out on a JEM 2010 operating at 200 keV. XRD measurements are conducted by a STADIP automated transmission diffractometer (STOE) equipped with an incident beam curved germanium monochromator selecting Cu Kα1 radiation and a 6° position sensitive detector (PSD). The XRD patterns are scanned in the 2θ range of 10−100°. For the data interpretation the software WinXpow (STOE) and the database of Powder Diffraction File (PDF) of the International Centre of Diffraction Data (ICDD) were used. Nitrogen adsorption−desorption isotherms were measured at 77 K using American Quantachrome iQ2 automated gas sorption analyzer. The pore-size distribution was calculated by Barrett, Joyner and Halenda (BJH) method from desorption isotherm. The contents of Cu and Ni in the catalysts were measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES), using an Iris advantage Thermo Jarrel Ash device. NMR spectra were measured using a Varian NMR system at 400 MHz (1H) and 101 MHz (13C). All spectra were recorded in d6-Acetone or CDCl3, and chemical shifts (δ) are reported in ppm relative to tetramethylsilane referenced to the residual solvent peaks. Extended X-ray absorption fine structure (EXAFS) experiments were performed at the Beijing Synchrotron Radiation Facility (BSRF) in Institute of High Energy Physics, Chinese Academy of Sciences with storage ring energy of 2.5 GeV and a beam current between 150 and 250 mA. The Cu K edge absorbance of powder catalysts was measured in transmission geometry at room temperature. The energy was scanned from −200 eV below to 800 eV above the Cu K edge (8979 eV). EXAFS data analysis was carried out using iffeffit analysis programs (http://cars9.uchicago.edu/ifeffit/). Catalytic activity test. The reaction of aniline with 1,6-hexanediol was chosen as a model reaction for catalyst screening and optimization of the reaction conditions. The reactions were performed in 15 mL pressure tubes under an argon atmosphere with a magnetic stirring speed of 450 rpm. Cycloamination reaction. 0.5 mmol amine, 1.0 mmol diol, 0.05 mmol NaOH, 100 mg catalyst, 2 mL mesitylene, 180 °C (oven temperature), 24 h. Monoamination reaction. 0.5 mmol amine, 1.0 mmol diol, 0.05 mmol NaOH, 25 mg catalyst, 2 mL mesitylene, 180 °C (oven temperature), 24 h. Diamination reaction. 2.5 mmol amine, 1.0 mmol diol, 0.1 mmol NaOH, 25 mg catalyst, 180 °C (oven temperature), 72 h. After completion of the reaction, the reaction tube was cooled to room temperature, and then 4 mL ethanol was added to dissolve the reaction mixture sufficiently. Subsequently, the reaction mixture was analyzed by GC-MS (Agilent 7890B/5977A) and GC-FID (Agilent 7890A), and the isolated yields were obtained by flash column chromatography.

Figure 1. XRD diffraction patterns of catalysts CuAlOx (a), NiAlOx (b), CuNiOx (c), and CuNiAlOx (d).

diffraction peaks of Cu(111), Cu(200), Cu(220), Cu(311), and Cu(222). Ni(111) (2θ = 44.8°), Ni(200) (2θ = 51.8°), Ni(220) (2θ = 76.4°), and Ni(311) (2θ = 92.9°) reflections indicate the presence of metallic Ni. Additionally, some Al2O3(311) (2θ = 37.0°) and Al2O3(111) (2θ = 66°) signals are also detected in samples CuAlOx, NiAlOx, and CuNiAlOx. It is noteworthy that the presence of Cu−Ni alloy in the CuNiOx and CuNiAlOx leads to the peak shifts. The diffraction peaks of Ni(220), Ni(311), and Ni(222) (2θ = 98.4°) manifested the coexistence of Cu−Ni alloy and metallic Ni in CuNiOx. The chemical state and surface composition of the samples were revealed by XPS. The XPS spectra of Cu 2p and Ni 2p given in Figure 2 indicated that Cu and Ni in the catalysts possibly existed in metallic Cu (932.4 and 952.2 eV) and NiO (853.3 and 871.7 eV). However, the peaks at 852.3 and 869.7 eV are assigned to the 2p orbit of the Ni0 species, which revealed the existence of metallic Ni in CuNiOx. This can be ascribed to the large particles of CuNiOx, which makes part of Ni hard to be oxidized. Therefore, it can be concluded that the dispersity of the other three catalysts is better due to the addition of AlOx; thus, the metallic Ni is easier to be oxidized. Nevertheless, the XRD results imply that the major Ni species exist as metallic Ni in the bulk phase. The morphologies and microstructures of the catalysts were examined by TEM, and the images are shown in Figure 3. The HR-TEM image shown in Figure 3h confirms the observations from XRD diffraction patterns and XPS spectra. The crystal lattices of Cu(111) and Ni(111) can be observed clearly. A Cu and Ni K-edge extended X-ray absorption fine structures (EXAFS) were analyzed to reveal the coordination environment of Cu and Ni in catalysts CuAlOx, NiAlOx, CuNiOx, and CuNiAlOx (Figure 4 and 5). It can be determined that the Cu species mainly exists in the form of metallic state or Cu−Ni alloy when compared to the standard spectra (Figure 4a, d−g). Unfortunately, the spectra of Cu foil and Cu−Ni alloy are almost overlapped so that it is hard to differentiate the existential state of Cu in CuNiOx and CuNiAlOx. The weak Ni−O peaks in all the catalysts demonstrated that the major Ni species may exist in the metallic state (Figure 5), which is also

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RESULTS AND DISCUSSION Catalyst characterization. To explore the correlation of structure and activity, the prepared catalysts were extensively characterized by ICP-AES, N2 adsorption−desorption analysis, XPS, XRD, EXAFS, and TEM. According to the ICP-AES analysis of CuAlOx (Cu/Al = 1:2.7), NiAlOx (Ni/Al = 2:2.7), CuNiOx (Cu/Ni = 1:2), and CuNiAlOx (Cu/Ni/Al = 1:2:2.7) catalysts, the Cu contents were 27.4%, 31.1%, and 18.6%, and the Ni loadings were 39.7%, 39.5%, and 33.2%, respectively. The molar ratio of Cu and Ni in CuNiAlOx is 1:1.93 because the solubility-product constant Ksp of Ni(OH)2 (2.0 × 10−15) is greater than Cu(OH)2 (2.2 × 10−20) and the loss of Ni is more than Cu in the process of washing. The BET surface areas of these catalysts were 275.55, 300.6, 33.13, and 203.7 m2/g, respectively. The XRD diffraction patterns of the catalysts are shown in Figure 1. The CuAlOx catalyst shows diffraction peaks at 43.3°, 50.4°, 74.1°, 89.9°, and 95.0°, which can be ascribed to the B

DOI: 10.1021/acssuschemeng.7b03373 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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ACS Sustainable Chemistry & Engineering

Figure 2. Cu 2p (A) and Ni 2p (B) spectra of catalysts CuAlOx (a), NiAlOx (b), CuNiOx (c), and CuNiAlOx (d).

Figure 4. Fourier transform (FT) of Cu K-edge EXAFS: Cu foil (a); CuO (b); Cu2O (c); Cu−Ni alloy (d); CuNiOx (e); CuAlOx (f); CuNiAlOx (g).

Figure 5. Fourier transform (FT) of Ni K-edge EXAFS: Ni foil (a); Ni2O3 (b); Cu−Ni alloy (c); CuNiOx (d); NiAlOx (e); CuNiAlOx (f).

Figure 3. TEM (a, c, e, g) and HR-TEM (b, d, f, h) images of the catalysts CuAlOx (a, b), NiAlOx (c, d), CuNiOx (e, f), and CuNiAlOx (g, h).

existence of Cu−Ni alloy possibly (Figure 5). The Ni K-edge EXAFS spectra of NiAlOx are similar to CuNiAlOx, and the peaks at 2.2 Å and 4.66 Å indicate that the main Ni species exists in the form of metallic Ni. Thus, it can be sure that the main Ni species in NiAlOx and CuNiAlOx should be a metallic state but Cu−Ni alloy in CuNiOx. Furthermore, we can

proved by the XRD results. Besides, the spectrum of CuNiOx is almost the same as that of Cu−Ni alloy, which manifests the C

DOI: 10.1021/acssuschemeng.7b03373 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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ACS Sustainable Chemistry & Engineering Table 1. Catalyst Screening and Reaction Conditions Optimizationa

Sel (%)b Entry

Catalysts

Catalyst loading (mg)

Conv (%)

1 2 3 4 5 6 7 8 9

CuNiAlOx CuNiAlOx CuNiAlOx CuNiAlOx CuNiAlOx CuNiAlOx CuAlOx NiAlOx CuNiOx

100 50 40 30 25 12.5 25 25 25

100 100 100 100 100 86 80 53 85

b

C1

M1

100 82 56 10

0 18 44 81 96 85 86 63 77

8 8 37 15

a Aniline (0.5 mmol), 1,6-hexanediol (1 mmol), NaOH (10 mol % to aniline), mesitylene (2 mL), 180 °C, 24 h. bDetermined by GC-FID without correction.

Table 2. Results of Cycloamination of 1,6-Hexanediola

ascertain that the Cu species in all catalysts are metallic Cu apart from some Cu−Ni alloy in CuNiOx. Following, the reaction of aniline with 1,6-hexanediol was chosen as a model for catalyst screening and reaction conditions optimization. As expected, we got the thermodynamics driven cyclization products in good yields (Table 1, entries 1−2). However, N-(6-hydroxyhexyl)aniline would be mainly formed if the amount of CuNiAlOx was decreased to 25 mg or even to 12.5 mg (entries 5−6). The best performance was observed with CuNiAlOx as catalyst among all the samples attempted (entries 5, 7−9). Noteworthy, the choice of bases was crucial for this reaction as the base is an important cocatalyst to promote the alcohol activation to generate the ketone/aldehyde intermediate in “hydrogen transfer reaction”23,33 (Table S2, entries 1−6). Solvents also play important roles, and it seems that solvents with high boiling point and low polarity may lead to high conversion and selectivity (entries 7− 12). Among the various solvents examined, 1,3,5-trimethylbenzene was the most suitable one and 96% GC yield of M1 was achieved. The scope and limitations of catalyst CuNiAlOx in N-alkyl azepane synthesis were explored with different amines. Typically, the yield of 1-phenylazepane was 81% (C1, Table 2, entry 1). Good to excellent results were also obtained if aniline derivatives with other substituting groups, such as -Me, -di-Me, -i-Pr, -n-Bu, and -tert-Bu were used as the starting materials. The yields of the desired products ranged from 74% to 91% (C2−C6, entries 2−6). The reaction of aliphatic amines can also be performed. For example, 1-butylazepane can be synthesized with 84% yield via the reaction of n-butylamine with 1,6-hexanediol (C7, entries 7). The cyclization reaction of cyclohexylamine was also realized, and 74% yield of the desired product was obtained (C8, entries 8). In addition, the monoamination of diols, i.e., 1,4-butane diol, 1,5-pentane diol, and 1,6-hexane diol, can be realized with the addition of 25 mg of CuNiAlOx catalyst (Table 3). First, a series of aromatic primary amines reacted with 1,6-hexanediol to obtain N-(6-hydroxyhexyl)anilines in isolated yields of 97%− 53% (M1-M7, entries 1−7). The yields of monoamination products of aniline with 1,5-pentanediol and 1,4-butanediol were 97% and 88% (M8-M9, entries 8−9). Good to excellent results, i.e., 80−95%, can also be obtained if secondary amines such as morpholine derivatives, piperazine derivatives, piper-

a Amine (0.5 mmol), 1,6-hexanediol (1 mmol), CuNiAlOx (100 mg), NaOH (10 mol % to amine), mesitylene (2 mL), 180 °C, C1, C7, C8, 24 h, C2−C6, 36 h. bIsolated yields. cDetermined by GC-FID without correction.

idine derivatives, and pyrrole were applied as the starting materials (M10−M18, entries 10−18). Aliphatic primary amines also can react smoothly with 1,6-hexanediol to give the desired products efficiently (M19−M21, entries 19−21). D

DOI: 10.1021/acssuschemeng.7b03373 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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ACS Sustainable Chemistry & Engineering Table 3. Results of Monoamination of 1,6-Hexanediola

Finally, the reusability of CuNiAlOx was tested by the reaction of 1,6-hexanediol and aniline. To our delight, 80% yield of N(6-hydroxyhexyl)aniline can still be obtained at the second run although longer reaction time is needed. ICP-AES test revealed that the contents of Cu and Ni decreased slightly from 18.6% and 33.2% to 16.8% and 29.9% after being used for two times. These results showed that the catalyst is relatively stable during the reaction, and it has potential to be reused. Noteworthy, the diamination of diols can be achieved too if increasing the molar ratio of amine and diols to 2.5:1 (Table 4). Table 4. Results of Diamination of 1,6-Hexanediola

a

Amine (2.5 mmol), 1,6-hexanediol (1 mmol), CuNiAlOx (25 mg), NaOH (10 mol % to 1,6-hexanediol), 180 °C, 24 h. bIsolated yields.

Typical amines including aniline and heterocyclic amines can react with diols smoothly to generate the desired products. For example, the isolated yield of N,N′-dipbenyl-1,6-hexyldiamine was 89% (entry 1), and 85−91% isolated yields to the diamination products can be obtained if typical heterocyclic amines such as piperidine and morpholine derivatives were used as the starting materials (entries 2−5). Finally, the amination of 1,6-hexanediol with ammonia was explored as hexane-1,6-diamine was the intermediate for Nylon-6 synthesis. As expected, the amination reaction occurred, but azepane was formed as the sole product due to the fast cyclization of 6aminohexan-1-ol or 1,6-hexanediamine. To elucidate the selectivity variation of the products with different catalyst loadings, a possible reaction mechanism was proposed in Scheme 2. For the cycloamination, the catalyst loading is sufficient enough (100 mg) that the diols can be dehydrogenized to dialdehydes, dehydrated to form imine, and then hydrogenated to achieve the cyclization product (Scheme 2 and Scheme S1). However, the diols can only be dehydrogenated on one side to form 6-hydroxyhexanal when the catalyst loading in the reaction mixture is inadequate; thus, the main reaction product is monoaminated ones (Scheme 2 and Scheme S2). The two reaction pathways are competitive. Besides, for diamination of diols, the presence of an excess amount of amine would react with dialdehydes fast so the cyclization reaction can be efficiently avoided (Scheme S3).

a

Amine (0.5 mmol), diols (1 mmol), CuNiAlOx (25 mg), NaOH (10 mol % to amine), mesitylene (2 mL), 180 °C, 24 h. bIsolated yields. c The catalyst was used at the second run and reacted for 32 h. dThe reaction time was extended to 36 h. eThe molar ratio of amine to diol is 5:1. fDetermined by GC-FID without correction. E

DOI: 10.1021/acssuschemeng.7b03373 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

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ACS Sustainable Chemistry & Engineering Scheme 2. Possible Reaction Mechanism for Reaction Selectivity Variation

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(2) Maxwell, G. Synthetic Nitrogen Products: A Practical Guide to the Products and Processes; Kluwer Academic Publishers: 2004. (3) Salvatorea, R. N.; Yoona, C. H.; Jung, K. W. Synthesis of Secondary Amines. Tetrahedron 2001, 57, 7785−7811. (4) Shen, X.; Buchwald, S. L. Rhodium-catalyzed Asymmetric Intramolecular Hydroamination of Unactivated Alkenes. Angew. Chem., Int. Ed. 2010, 49 (3), 564−567. (5) Perl, N. R.; Ide, N. D.; Prajapati, S.; Perfect, H. H.; Duron, S. G.; Gin, D. Y. Annulation of Thioimidates and Vinyl Carbodiimides to Prepare 2-Aminopyrimidines, Competent Nucleophiles for Intramolecular Alkyne Hydroamination. Synthesis of (−)-Crambidine. J. Am. Chem. Soc. 2010, 132, 1802−1803. (6) Hesp, K. D.; Tobisch, S.; Stradiotto, M. [Ir(COD)Cl]2 as a Catalyst Precursor for the Intramolecular Hydroamination of Unactivated Alkenes with Primary Amines and Secondary Alkyl- or Arylamines: A Combined Catalytic, Mechanistic, and Computational Investigation. J. Am. Chem. Soc. 2010, 132, 413−426. (7) Ahmed, M.; Seayad, A. M.; Jackstell, R.; Beller, M. Amines Made Easily: A Highly Selective Hydroaminomethylation of Olefins. J. Am. Chem. Soc. 2003, 125, 10311−10318. (8) Vieira, T. O.; Alper, H. Rhodium(I)-catalyzed Hydroaminomethylation of 2-isopropenylanilines as a Novel route to 1,2,3,4tetrahydroquinolines. Chem. Commun. 2007, 26, 2710−2711. (9) Watson, A. J.; Williams, J. M. J. Chemistry. The Give and Take of Alcohol Activation. Science 2010, 329 (5992), 635−636. (10) Hamid, M. H. S. A.; Allen, C. L.; Lamb, G. W.; Maxwell, A. C.; Maytum, H. C.; Watson, A. J. A.; Williams, J. M. J. Rutheniumcatalyzed N-Alkylation of Amines and Sulfonamides Using Borrowing Hydrogen Methodology. J. Am. Chem. Soc. 2009, 131, 1766−1774. (11) Nixon, T. D.; Whittlesey, M. K.; Williams, J. M. Transition Metal Catalysed Reactions of Alcohols Using Borrowing Hydrogen Methodology. Dalton Trans. 2009, 5, 753−762. (12) Guillena, G.; Ramon, D. J.; Yus, M. Alcohols as Electrophiles in C–C Bond-forming Reactions: the Hydrogen Autotransfer Process. Angew. Chem., Int. Ed. 2007, 46 (14), 2358−2364. (13) Hamid, M. H. S. A.; Slatford, P. A.; Williams, J. M. J. Borrowing Hydrogen in the Activation of Alcohols. Adv. Synth. Catal. 2007, 349 (10), 1555−1575. (14) Yuan, K.; Jiang, F.; Sahli, Z.; Achard, M.; Roisnel, T.; Bruneau, C. Iridium-Catalyzed Oxidant-free Dehydrogenative C-H Bond Functionalization: Selective Preparation of N-Arylpiperidines through Tandem Hydrogen Transfers. Angew. Chem., Int. Ed. 2012, 51 (35), 8876−8880. (15) Fujita, K.-i.; Fujii, T.; Yamaguchi, R. Cp*Ir Complex-Catalyzed N-Heterocyclization of Primary Amines with Diols: A New Catalytic System for Environmentally Benign Synthesis of Cyclic Amines. Org. Lett. 2004, 6, 3525−3528.

CONCLUSIONS In conclusion, the controllable amination reactions of C4−C6 diols with amines were realized with CuNiAlOx as catalyst. Cycloamination, monoamination, and diamination can be selectively obtained by simply varying the catalyst loadings in the range 12.5−100 mg. To the best of our knowledge, this is the first time that diols were efficiently and selectively monoaminated without cyclization in good to excellent yields. This offers an efficient and environmentally friendly method for the synthesis of monoaminated alcohols.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b03373. Tables of physical properties and reaction conditions; N2 adsorption−desorption analysis; borrowing hydrogen strategy; and NMR data of the products (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Feng Shi: 0000-0001-5665-4933 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the National Key Research and Development Program of China (2017YFA0403100), National Natural Science Foundation of China (21633013), and Key Research Program of Frontier Sciences of CAS (QYZDJ-SSW-SLH051). We thank Lirong Zheng at the Institute of High Energy Physics, Chinese Academy of Sciences for helping us to perform the EXAFS analysis.

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REFERENCES

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DOI: 10.1021/acssuschemeng.7b03373 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX