Reaction Mechanism of Aromatic Ring Amination of Benzene and

Subscriber access provided by Library, Special Collections and Museums, University of Aberdeen

Article

Reaction Mechanism of Aromatic Ring Amination of Benzene and Substituted Benzenes by Aqueous Ammonia over Platinum-Loaded Titanium Oxide Photocatalyst Hayato Yuzawa, Jun Kumagai, and Hisao Yoshida J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/jp3127658 • Publication Date (Web): 29 Mar 2013 Downloaded from http://pubs.acs.org on April 4, 2013

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Reaction Mechanism of Aromatic Ring Amination of Benzene and Substituted Benzenes by Aqueous Ammonia over Platinum-Loaded Titanium Oxide Photocatalyst Hayato Yuzawa,†, ‡ Jun Kumagai,† and Hisao Yoshida*,† †

Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 4648603, Japan

[email protected]. AUTHOR FOOTNOTE Corresponding author *To whom correspondence should be addressed. Tel: +81-52-789-4609. Fax: +81-52-789-3178. E-mail: [email protected] Present address ‡

Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 41

Abstract Reaction mechanism of photocatalytic aromatic ring amination of benzene and the derivatives with aqueous ammonia was clarified by some reaction experiments and ESR spectroscopy as follows: a platinum-loaded titanium oxide photocatalyst oxidizes an ammonia to form an amide radical (·NH2) and a proton, and the amide radical attacks an aromatic ring to produce an intermediate, followed by the abstraction of the hydrogen atom from it on the platinum sites to produce an aniline. Simultaneously, the photocatalyst also promotes the reduction of a proton to form a hydrogen radical on the platinum sites, and it reacts with the abstracted hydrogen to produce a molecular hydrogen. The photocatalytic aromatic ring amination proceeded for many kinds of monosubstituted benzenes except for phenol, and high selectivity was recorded for benzonitrile and halogenated benzenes. It is noted that the distributions of the aminated isomers were unique, i.e., the para-isomer was predominantly produced in the case of nitrobenzene, and ortho-isomers were preferentially produced in the case of the other substrates, which would depend on the approaching direction of the molecular to the photocatalyst surface.

KEYWORDS Direct amination of aromatic ring, aqueous ammonia, titanium oxide photocatalyst, isotopic effect, reaction mechanism, isomer distribution of anilines


2

Page 3 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Introduction Anilines are important chemical intermediates for resins, medicines, and so on. These are mainly synthesized through nitration of aromatic ring with mixed acid followed by hydrogenation of the obtained nitroaromatics under high temperature.1 However, we must consider that the high yield and high selectivity for anilines given in this process are achieved at the expense of the large amount of the mixed acid and the huge energy to maintain the high temperature.1 Thus, in view of green and sustainable chemistry, new methodologies have been examined to realize simple and direct amination of aromatic ring. So far, various combinations of amination reagents and catalysts have been reported.2–20 For example, Kovacic et al. reported the direct aromatic ring amination through the Friedel-Crafts type reaction by using halamines with aluminum halide.2,3 Hydroxyl amine was also used as an amination reagent with transition metal componds,4 vanadium-based supported catalysts,5 Mn-MCM-41,6 and so on. These electrophilic amination reagents can preferably attack the aromatic ring. On the other hand, some basecatalyzed nucleophilic amination reagents have been also reported such as 4-amino-1,2,4-triazole,7 sulfonamides,8 methoxyamine,9 and 1,1,1-trimethyl hydrazine iodide,10 although they were limited for nitro-substituted aromatic compounds. All of these amination reagents can selectively aminate the aromatic ring, but the extra processes are still required to synthesize these special reagents and also to separate the elimination group as necessary. In contrast to them, ammonia is an ideal amination reagent to solve these problems. It has been already reported that the direct aromatic ring amination by using ammonia (eq 1) can proceed over various catalysts such as Ni/NiO/ZrO2.11–18

(1)


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 41

However, since this reaction is endergonic (∆G0298K = 53.7 kJ mol-1), the yield of aniline is still low (97%) was not influenced by the platinum loading amount. In addition, the ammonia efficiency, which was the ratio of the amount of aniline to the consumed ammonia, were also almost constant (16–19%), where the value for the Pt(1.0)/TiO2(R) sample could not be calculated due to the lack of detectable hydrogen. With the Pt(1.0)/TiO2(R) sample, most of the produced hydrogen would be consumed for the hydrogenation. Also in the case of the Pt(x)/TiO2(A) samples, the ACS Paragon Plus Environment

8

Page 9 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


same feature as the Pt(x)/TiO2(R) sample was observed. Thus, x = 0.1 wt % was the optimum loading amount of the platinum cocatalyst on these titanium oxide photocatalysts for this reaction. Figure 2a shows the time course of the products yield in the aromatic ring amination tests over the Pt(0.1)/TiO2(R) sample as the representative. All of the products proportionally increased with the reaction time until 6 h. Then, the production rate of aniline decreased after 6 h and the aniline yield decreased from 12 h to 24 h without any formation of decomposed products from aniline. After the reaction for 24 h, a trace amount of diphenylamine (99%) was attained at the lowest temperature (Table 4, entry 4). As described above, the Pt(0.1)/TiO2(A) sample exhibited higher aniline selectivity by the limitation of the irradiated light wavelength to 365±20 nm (Table 1, entry 6) than that without the wavelength limitation (Table 1, entry 1), where the reaction temperature (300 K) was lower than that under irradiation without wavelength limitation (314 K). This temperature effect would partly contribute to the high selectivity as well as the limitation of the direct photoactivation of benzene, as reported in literature.34, 35 On the other hand, with the Pt(0.1)/TiO2(R) sample, phenol was hardly detected even if the reaction temperature increased to 323 K (Table 4, entries 5 and 6). This result indicates that the phenol production could not proceed over the Pt(0.1)/TiO2(R) under the present condition. Since the valence band-edge potential of rutile (3.04 V43 vs NHE) was more negative than that of anatase (3.12 V42), this would be because the photocatalytic oxidation of water (H2O + h+ → ·OH + H+, 2.8 V vs NHE)45 over the rutile phase proceeds more hardly than that over the anatase phase, as reported in the previous study.35


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 41

3.5. Proposed Reaction Mechanism of the Aromatic Ring Amination of Benzene. Based on the above investigations, the dominant reaction mechanism of the aromatic ring amination of benzene was summarized in Figure 4. In the aqueous ammonia solution (pH = 13.1) the surface of titanium oxide should be negatively charged. The isotopic experiment and the influence of reaction temperature in this study also supports that ammonia is dominantly adsorbed on the active sites of the titanium oxide surface, and benzene would approach to the ammonia-covered surface in this reaction condition (Figure 4i). It was reported that a direct interaction between benzene and ammonia on the titanium oxide was observed by using a FT-IR spectroscopy.46 Further, the adsorption states of ammonia were also reported.37 Considering this adsorption state, the appropriate reaction mechanism of the aromatic ring amination would be categorized as the Rideal-Eley mechanism. The adsorbed species on the titanium oxide surface in the vicinity of the platinum nanoparticles would most contribute the amination reaction. Photoexcitation of titanium oxide induces to produce a photoexcited electron and a hole. The former migrates to platinum, and the latter is trapped by deprotonated terminal hydroxyl group (eq 10, Figure 4ii).40 The trapped hole induces the N–H bond cleavage in the adsorbed ammonia to produce the amide radical (eq 11, Figure 4iii), which was supported by the ESR and the isotopic experiments. This step is the rate determining step for the photocatalytic aromatic ring amination. The produced amide radical attacks the aromatic ring to produce the intermediate (eq 12), while the photoexcited electron reduces a proton to produce a hydrogen radical (Figure 4iv). Finally, the hydrogen of the intermediate was abstracted by the platinum sites to produce an aniline (eq 13, Figure 4v), and the abstracted hydrogen reacts with the hydrogen radical on the platinum sites to produce a molecular hydrogen (eq 13, Figure 4vi). The hydrogen abstracted from ammonia by the surface oxygen is eliminated as a proton by base such as hydroxide ion (OH-) or ammonia (Figure 4vii).

3.6. Aromatic Ring Amination of Substituted Benzenes. When the photocatalytic reaction tests were carried out for various monosubstituted benzenes over the Pt(0.1)/TiO2(A) sample without wavelength limitation, aminated products selectivity was low (2.6–51%) for all of the monosubstituted benzenes ACS Paragon Plus Environment

16

Page 17 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


except for benzonitrile (87%) because the direct activation of monosubstituted benzenes could take place to form some kinds of dimer products via coupling. However, the dimer products derived from the coupling of two phenyl radicals were not produced. This would be because the amide radical did not have enough reactivity for the C–H bond of the aromatic ring as discussed in the case of benzene (section 3.3). Under the light of limited wavelength (365±20 nm), benzonitrile and halogenated benzenes were aminated as well as benzene with high selectivity such as 76–92% (Table 5, entries 2–6). The amination also proceeded on toluene, anisole and aniline, although some kinds of reactions occurred at each substituent and the amination selectivity was low for each compound (8.4–30%, Table 5, entries 7–9) due to reactions of the substituent (transformation of the substituent and coupling reaction through the substituent). These results indicate that the amide radical could activate these substituents (i.e., the C−H bond in the methyl group and the methoxy group, and the N−H bond in the amino group). In fact, the bond energies of the C−H bond in the methyl group of toluene, the C−H bond in methoxy group of anisole and the N−H bond in amino group of aniline were 375.5±5.0, 385 and 375.3 kJ mol-1 at 298 K,38 respectively, which is lower than the bond energies of the N−H bond in ammonia (452.7±1.3 kJ mol-1 at 298 K38). In the case of nitrobenzene, the selectivity for the aminated products was low (8.2%, Table 5, entry 1) because both nitrobenzene and the aminated product were hydrogenated by the produced hydrogen (or hydrogen radical) to produce aniline, nitrosobenzene, azoxybenzene and phenylenediamine. In the case of benzonitrile, byproduct was benzamide only (Table 5, entry 2). Almost the same quantity of benzamide was formed by mixing of benzonitrile and aqueous ammonia solution without photocatalyst in the dark for 3 h, and the yield of benzamide did not increase with increasing the reaction time. This result indicates that benzamide could be produced from hydration of benzonitrile under the basic condition and the reaction achieved equilibrium. Thus, the photocatalytic amination selectivity would increase with the increase in the yield of the aminated products, e.g., the aminated products selectivity increased to 87% (0.063% yield) upon photoirradiation with a high light intensity without wavelength limitation for the same reaction time. In the case of phenol, no aminated products were obtained, and the amount of hydrogen produced from ammonia ACS Paragon Plus Environment

17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 41

decomposition was the lowest (Table 5, entry 10). The color of the photocatalyst changed from light gray to yellow, which was assigned to the surface Ti−O−Ph species.47 Because of this species bonding to the surface,48 the activation of ammonia to produce amide radical might be inhibited. Or, if the aminated products were formed, they might be unable to desorb from the surface. Figure 5a shows the yield and the selectivity of the aminated products produced from the monosubstituted benzenes listed in the order of the electron withdrawing/donating property of substituent. Among these substrates, aniline provided the largest amount of aminated products (Figure 5a). This is probably due to the largest solubility of aniline in the aqueous ammonia. There is no clear relationship between the electron withdrawing/donating property of these substituent and the aminated products yield, meaning that the attack of the active species in this reaction was not affected by the electron density of the aromatic ring. If the active species were the electrophilic ammonia radical cation (·NH3+), a clear relationship should be observed between the aminated products yield and the electron withdrawing/donating property of substituent.49 This fact further supports that the dominant active species is the neutral amide radical (·NH2). Figure 5b shows the isomer distribution of the aminated products. It is expected that the electroneutral property of the amide radical should result in ortho-para or non-selective orientation.50 However, it is very interesting that two types of unique isomer distribution were observed; one is that only the para-isomer was produced from nitrobenzene (>99%), and the other is that ortho-isomers were preferentially produced from other substrates (40–79%, Figure 5b). The obtained distribution was not dependent on the platinum loading amount (see Figure S2a−c) and the kind of loading metal (see Figure S2d). In the former case, the nitro group has strongly negative charge on the oxygen atom compared to the other substrates, and the titanium oxide surface was negatively charged in the alkaline solution, so that the repulsion between them would make the nitrobenzene to be adsorbed preferentially at the para-position of the aromatic ring on the surface and to form the para- isomer selectively. In our previous study of aromatic ring hydroxylation, we already clarified that the interaction between the negative charge on the titanium oxide surface and the polarization of monosubstituted benzenes ACS Paragon Plus Environment

18

Page 19 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


influenced the isomer distribution of the hydroxylated products in the basic condition.35 However, in the latter case (the substrates having the less polarized substituent than nitrobenzene), the different feature for the isomer distribution of the aminated products from the case of nitrobenzene could not be explained by the repulsion. Thus, other factors should be considered for the preference of ortho- isomer. The following factors could be additionally discussed: the steric hindrance by the substituent, electron density of frontier orbital (HOMO and LUMO) of the substrate, and the interaction between the substrate and the ammonia. In order to clarify the contribution of these factors, we examined the reaction tests for the amination of dichlorobenzenes and m-xylene (Table 6). When 1,2-dichlorobenzene was used as a substrate, amino group was preferentially introduced to α-carbons (3 or 6-position) at high selectivity (88 %, Table 6, entry 1). This feature is consistent with the results of mono-substituted benzenes in Figure 5. For 1,3dichlorobenzene, amino group predominantly substituted at α1-carbon (2-position) at high selectivity (53 %, Table 6, entry 2). This selectivity was also observed for m-xylene (Table 6, entry 3). The results shown in Figure 5 and Table 6 clearly indicate that the amino group is preferentially introduced to the carbon next to the substituent-linked carbon and more preferentially introduced to the carbon surrounded by two substituent-linked carbons than that next to one substituent-linked carbon. The carbon surrounded by two substituent-linked carbons was the largest steric hindrance for the approach of the amide radical. Thus, the steric hindrance of the substituent is not an important factor for the isomer distribution of the aromatic ring amination. Table 6 also shows the C(2pz) orbital coefficient in the frontier orbitals (the HOMO and the LUMO) of each substrate, which were calculated by MOPAC 2009.51,52 It seems that these values were not correlated with the distribution of amino group. On the other hand, in the photocatalytic aromatic ring hydroxylation promoted by an electrophilic attack of an hydroxyl radical,35 the hydroxyl radical was preferentially introduced to the carbon having larger orbital coefficient at the HOMO as shown in Table 6, i.e., the position selectivity of the hydroxyl group was dominantly determined by the electron density of the frontier orbital. Thus, in the present photocatalytic amination, it was confirmed that the electron ACS Paragon Plus Environment

19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 41

density of the frontier orbital was also not an important factor for the isomer distribution of the aromatic ring amination. As for the interaction between the substrate and the ammonia, there are the attractive interactions of weak hydrogen bond between the hydrogen of ammonia and π orbital of aromatic ring (hydrogen−π interaction)53 or the substituent (hydrogen−substituent interaction),54 which were reported in the case of fluorobenzene53,54 in a gas phase. The hydrogen−π interaction could not explain the obtained unique distribution (Figure 5 and Table 6) and the negatively charged surface of titanium oxide would not prefer the hydrogen−π interaction. On the other hand, the hydrogen−substituent interaction could explain it, because this interaction decreases the influence of the steric hindrance of the substituent and increases the possibility to keep the produced amide radical in the vicinity of the substituent. The orthoposition is the nearest carbon except for the substituent-linked carbon. Thus, the hydrogen−substituent interaction would preferentially influence the position selectivity of amino group substitution in the substituted benzene except for the nitrobenzene. From these discussions, proposed mechanisms for the unique orientation of amino group are shown in Figure 6. Since the amide radical has neutral property (Figure 5), which is different from hydroxyl radical having electrophilic property (Table 6),35 the orientation of the amino group is influenced by the interaction between the substrate, ammonia and the negatively charged titanium oxide surface. In the case of nitrobenzene, which is the most negatively polarized at the substituent, the repulsion between the negatively charged substituent and the negatively charged titanium oxide surface in the basic condition makes nitrobenzene approach the titanium oxide surface from the para-position, then the amide radical dominantly attacks at the para-position to produce the para-isomer of the aminated product (Figure 6a). In the case of the other substrates, which are less polarized than nitrobenzene, the interaction (hydrogen bond) between the hydrogen of ammonia and the substituent leads the ammonia adsorbed on the titanium oxide to the vicinity of the substrate to produce ortho-isomer of the aminated product (Figure 6b).


20

Page 21 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4. Conclusion The reaction mechanism of the photocatalytic direct amination of aromatic ring with aqueous ammonia solution on the platinum-loaded titanium oxide photocatalyst is proposed as follows: a photoformed hole on the titanium oxide surface oxidizes an ammonia to form a neutral amide radical, which react with the aromatic ring to form an intermediate, while a photoformed electron on the platinum sites reduces a proton to form a hydrogen radical. The hydrogen of the intermediate is abstracted by the platinum sites to produce the aminated product, and the abstracted hydrogen reacts with the hydrogen radical to produce a molecular hydrogen on the platinum sites. Several kinds of mono- and disubstituted benzenes were also examined for this reaction. The paraisomer was predominantly produced in the case of nitrobenzene, while the carbon next to the substituent-linked carbon was preferentially aminated in the other monosubstituted benzenes, and disubstituted benzene (dichlorobenzenes and m-xylene). These results reveal that two factors, i.e., the coulomb charge repulsion between the titanium oxide surface and the substituent, and/or the hydrogen bond between the ammonia and the substituent, would affect the position selectivity in this photocatalytic aromatic ring amination.

ACKNOWLEDGMENT We thank to Dr. N. Endo (The Wakasa Wan Energy Research Center) for the valuable advices for the ESR measurements. This research was financially supported by Grant-in-Aid for JSPS fellows (22– 7799) and the fund for doctoral students in Nagoya University.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 41

References (1) Downing, R. S.; Kunkeler, P. J.; van Bekkum, H. Catalytic Syntheses of Aromatic Amines. Catal. Today 1997, 37, 121–136. (2) Kovacic, P.; Goralski, C. T.; Hiller, J. J. Jr.; Levisky, J. A.; Lange, R. M. Amination of Toluene with Trichloramine-Lewis Acid Catalyst. J. Am. Chem. Soc. 1965, 87, 1262–1266. (3) Kovacic, P.; Levisky, J. A. Relative Reactivities in Amination of Benzene and Alkylbenzenes with Trichloramine-Aluminum Bromide. Evidence for σ Substitution. J. Am. Chem. Soc. 1966, 88, 1000–1005. (4) Kuznetsova, N. I.; Kuznetsova, L. I.; Detusheva, L. G.; Likholobov, V. A.; Pez, G. P.; Cheng, H. Amination of Benzene and Toluene with Hydroxylamine in the Presence of Transition Metal Redox Catalysts. J. Mol. Catal. A 2000, 161, 1–9. (5) Yu, T.; Hu, C.; Wang, X. Direct Amination of Toluene with Hydroxylamine in the Presence of Vanadium-based Catalysts. Chem. Lett. 2005, 34, 406–407. (6) Parida, K. M.; Dash, S. S.; Singha, S. Structural Properties and Catalytic Activity of Mn-MCM-41 Mesoporous Molecular Sieves for Single-Step Amination of Benzene to Aniline. Appl. Catal., A 2008, 351, 59–67. (7) Katritzky, A. R.; Laurenzo, K. S. Direct Amination of Nitrobenzenes by Vicarious Nucleophilic Substitution. J. Org. Chem. 1986, 51, 5039–5040. (8) Mąosza, M.; Bialecki, M. Amination of Nitroarenes with Sulfenamides via Vicarious Nucleophilic Substitution of Hydrogen. J. Org. Chem. 1992, 57, 4784–4785. (9) Seko, S.; Kawamura, N. Copper-Catalyzed Direct Amination of Nitrobenzenes with OAlkylhydroxylamines. J. Org. Chem. 1996, 61, 442–443. (10) Pagoria, P. F.; Mitchell, A. R.; Schmidt, R. D. 1,1,1-Trimethylhydrazinium Iodide: A Novel, Highly Reactive Reagent for Aromatic Amination via Vicarious Nucleophilic Substitution of Hydrogen. J. Org. Chem. 1996, 61, 2934–2935. ACS Paragon Plus Environment

22

Page 23 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(11) Wibaut, J. P. Zur Bildung von Anilin aus Ammoniak und Benzol bei hohen Temperaturen Anwesenheit von Kontaktsubstanzen. Chem. Ber. 1917, 50, 541–546. (12) Thomas, C. L. Preparation of Aromatic Amines. Canadian Pat. 553988, 1958. (13) Schmerling, L. Preparation of Aromatic Amines. US Pat. 2, 948, 755, 1960. (14) DelPesco, T. W. Synthesis of Aromatic Amines by Reaction of Aromatic Compounds with Ammonia. US Pat. 4, 031, 106, 1977. (15) Hara, Y. Methods for Amination and Cyanation of Aromatic Compounds (Japanese), JP. 6– 293715, 1994. (16) Becker, J.; Hölderich, W. F. Amination of Benzene in the Presence of Ammonia Using a Group VIII Metal Supported on a Carrier as Catalyst. Catal. Lett. 1998, 54, 125–128. (17) Desrosiers, P.; Guan, S.; Hagemeyer, A.; Lowe, D. M.; Lugmair, C.; Poojary, D. M.; Turner, H.; Weinberg, H.; Zhou, X.; Armbrust, R.; Fengler, G.; Notheis, U. Application of Combinatorial Catalysis for the Direct Amination of Benzene to Aniline. Catal. Today 2003, 81, 319–328. (18) Hoffmann, N.; Muhler, M. On the Mechanism of the Oxidative Amination of Benzene with Ammonia to Aniline over NiO/ZrO2 as Cataloreactant. Catal. Lett. 2005, 103, 155–159. (19) Fox, M. A.; Dulay, M. T. Heterogeneous Photocatalysis. Chem. Rev. 1993, 93, 341–357. (20) Maldotti, A.; Molinari, A.; Amadelli, R. Photocatalysis with Organized Systems for the Oxofunctionalization of Hydrocarbons by O2. Chem. Rev. 2002, 102, 3811–3836. (21) Carp, O.; Huisman, C. L.; Reller, A. Photoinduced Reactivity of Titanium Dioxide. Prog. Solid State Chem. 2004, 32, 33–177. (22) Palmisano, G.; Augugliaro, V.; Pagliaro, M.; Palmisano, L. Photocatalysis: A Promising Route for 21st Century Organic Chemistry. Chem. Commun. 2007, 3425–3437. (23) Shiraishi, Y.; Hirai, T. Selective Organic Transformations on Titanium Oxide-Based Photocatalysts. J. Photochem. Photobiol., C 2008, 9, 157–170.


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 41

(24) Ohtani, B.; Osaki, H.; Nishimoto, S.; Kagiya, T. A Novel Photocatalytic Process of Amine NAlkylation by Platinized Semiconductor Particles Suspended in Alcohols. J. Am. Chem. Soc. 1986, 108, 308–310. (25) Miyama, H.; Nosaka, Y.; Fukushima, T.; Toi, H. Photocatalytic Production of Amines from Alcohols and Aqueous Ammonia. J. Photochem. 1987, 36, 121–123. (26) Matsushita, Y.; Ohba, N.; Suzuki, T.; Ichimura, T. N-Alkylation of Amines by Photocatalytic Reaction in a Microreaction System. Catal. Today 2008, 132, 153–158. (27) Mahdavi, F.; Bruton, T. C.; Li, Y. Photoinduced Reduction of Nitro Compounds on Semiconductor Particles. J. Org. Chem. 1993, 58, 744–746. (28) Ferry, J. L.; Glaze, W. H. Photocatalytic Reduction of Nitro Organics over Illuminated Titanium Dioxide: Role of the TiO2 Surface. Langmuir 1998, 14, 3551–3555. (29) Maldotti, A.; Andreotti, L.; Molinari, A.; Tollari, S.; Penoni, A.; Cenini, S. Photochemical and Photocatalytic Reduction of Nitrobenzene in the Presence of Cyclohexene. J. Photochem. Photobiol., A 2000, 133, 129–133. (30) Flores, S. O.; Rios-Bernij, O.; Valenzuela, M. A.; Córdova, I.; Gómez, R.; Gutiérrez, R. Photocatalytic Reduction of Nitrobenzene over Titanium Dioxide: By-Product Identification and Possible Pathways. Top.Catal. 2007, 44, 507–511. (31) Imamura, K.; Iwasaki, S.; Maeda, T.; Hashimoto, K.; Ohtani, B.; Kominami, H. Photocatalytic Reduction of Nitrobenzenes to Aminobenzenes in Aqueous Suspensions of Titanium(IV) Oxide in the Presence of Hole Scavengers under Deaerated and Aerated Conditions. Phys. Chem. Chem. Phys. 2011, 13, 5114–5119. (32) Tada, H.; Ishida, T.; Takao, A.; Ito, S.; Mukhopadhyay, S.; Akita, T.; Tanaka, K.; Kobayashi, H. Kinetic and DFT Studies on the Ag/TiO2-Photocatalyzed Selective Reduction of Nitrobenzene to Aniline. ChemPhysChem 2005, 6, 1537–1543. (33) Yuzawa, H.; Yoshida, H. Direct Aromatic-Ring Amination by Aqueous Ammonia with a Platinum Loaded Titanium Oxide Photocatalyst. Chem. Commun. 2010, 46, 8854–8856. ACS Paragon Plus Environment

24

Page 25 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(34) Yoshida, H.; Yuzawa, H.; Aoki, M.; Otake, K.; Itoh, H.; Hattori, T. Photocatalytic Hydroxylation of Aromatic Ring by Using Water as an Oxidant. Chem. Commun. 2008, 4634–4636. (35) Yuzawa, H.; Aoki, M.; Otake, K.; Itoh, H.; Hattori, T.; Yoshida, H. Reaction Mechanism of Aromatic Ring Hydroxylation by Water over Platinum-Loaded Titanium Oxide Photocatalyst. J. Phys. Chem. C 2012, 116, 25376–25387. (36) Nemoto, J.; Gokan, N.; Ueno, H.; Kaneko, M. Photodecomposition of Ammonia to Dinitrogen and Dihydrogen on Platinized TiO2 Nanoparticules in an Aqueous Solution. J. Photochem. Photobiol., A 2007, 185, 295–300. (37) Yuzawa, H.; Mori, T.; Itoh, H.; Yoshida, H. Reaction Mechanism of Ammonia Decomposition to Nitrogen and Hydrogen over Metal Loaded Titanium Oxide Photocatalyst. J. Phys. Chem. C 2012, 116, 4126–4136. (38) Lide, D. R. Handbook of chemistry and physics, 84th ed.; CRC Press: London, 2003. (39) Chignell, C. F.; Kalyanaraman, B.; Sik, R. H.; Mason, R. P. Spectroscopic Studies of Cutaneous Photosensitizing Agents-II. Spin Trapping of Photolysis Products from Sulfanilamide and 4Aminobenzoic Acid Using 5,5-Dimethyl-1-Pyrroline-1-Oxide Photochem. Photobiol. 1981, 34, 147–156. (40) Imanishi, A.; Okamura, T.; Ohashi, N.; Nakamura, R.; Nakato, Y. Mechanism of Water Photooxidation Reaction at Atomically Flat TiO2 (Rutile) (110) and (100) Surfaces: Dependence on Solution pH. J. Am. Chem. Soc. 2007, 129, 11569–11578. (41) Yamazoe, S.; Teramura, K.; Hitomi, Y.; Shishido, T.; Tanaka, T. Visible Light Absorbed NH2 Species Derived from NH3 Adsorbed on TiO2 for Photoassisted Selective Catalytic Reduction. J. Phys. Chem. C 2007, 111, 14189–14197. (42) Duonghong, D.; Ramsden, J.; Grӓtzel, M. Dynamics of Interfacial Electron-Transfer Processes in Colloidal Semiconductor Systems. J. Am. Chem. Soc. 1982, 104, 2977–2985.


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 41

(43) Shiga, A.; Tsujiko, A.; Yae, S.; Nakato, Y. High Photocurrent Quantum Yields in Short Wavelengths for Nanocrystalline Anatase-Type TiO2 Film Electrodes Compared with Those Rutile-Type. Bull. Chem. Soc. Jpn. 1998, 71, 2119–2125. (44) Shimura, K.; Maeda, K.; Yoshida, H. Thermal Acceleration of Electron Migration in Gallium Oxide Photocatalysts. J. Phys. Chem. C, 2011, 115, 9041–9047. (45) Jaeger, C. D.; Bard, A. J. Spin Trapping and Electron Spin Resonance Detection of Radical Intermediates in the Photodecomposition of Water at TiO2 Particulate Systems. J. Phys. Chem. 1979, 83, 3146–3152. (46) Hadjiivanov, K.; Klissurski, D.; Busca, G.; Lorenzelli, V. Benzene-Ammonia Coadsorption on TiO2(Anatase). J. Chem. Soc., Faraday Trans. 1991, 87, 175–178. (47) Usseglio, S.; Calza, P.; Damin, A.; Minero, C.; Bordiga, S.; Lamberti, C.; Pelizzetti, E.; Zecchina, A. Tailoring the Selectivity of Ti-Based Photocatalysts (TiO2 and Microporous ETS-10 and ETS4) by Playing with Surface Morphology and Electronic Structure. Chem. Mater. 2006, 18, 3412– 3424. (48) Yuzawa, H.; Aoki, M.; Itoh, H.; Yoshida H. Adsorption and Photoadsorption States of Benzene Derivatives on Titanium Oxide Studied by NMR. J. Phys. Chem. Lett. 2011, 2, 1868–1873. (49) Citterio, A.; Gentile, A.; Minisci, F.; Navarrini, V.; Serravalle, M.; Ventura, S. Polar Effects in Free Radical Reactions. Homolytic Aromatic Amination by the Amino Radical Cation, ·+NH3: Reactivity and Selectivity. J. Org. Chem. 1984, 49, 4479–4482. (50) Fukui, K.; Yonezawa, T.; Nagata, C.; Shingu, H. Molecular Orbital Theory of Orientation in Aromatic, Heteroaromatic, and Other Conjugated Molecules. J. Chem. Phys. 1954, 22, 1433–1442. (51) Stewart, J. J. P. MOPAC, version 8.331W; Stewart Computational Chemistry: Colorado Springs, CO, 2007; see http://openmopac.net/. (52) Stewart, J. J. P. Optimization of Parameters for Semiempirical Methods V: Modification of NDDO Approximations and Application to 70 Elements. J. Mol. Model. 2007, 13, 1173–1213.


26

Page 27 of 41

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(53) Vaupel, S.; Brutschy, B.; Tarakeshwar, P.; Kim K. S. Characterization of Weak NH-π Intermolecular Interactions of Ammonia with Various Substituted π-Systems. J. Am. Chem. Soc. 2006, 128, 5416–5426. (54) Tonge, N. M.; MacMahon, E. C.; Pugliesi, I.; Cockett, M. C. The Weak Hydrogen Bond in the Fluorobenzene-Ammonia Van der Waals Complex: Insights into the Effects of Electron Withdrawing Substituents on π Versus In-Plane Bonding J. Chem. Phys. 2007, 126, 154319.


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 41

Table 1. Results of the Photocatalytic Aromatic Ring Amination of Benzene over the TiO2(A) Sample and the Pt(0.1)/TiO2 Samplesa

products / µmol entry

a

sample

substrate

aniline yieldb

aniline selectivityc

aniline

phenol

biphenyl

H2/HD/D2

N2

(10-2%)

(%)

133/–/–d

–d

6.4

51

–d

0.88

–

8.3

2.8

>97

8.0

2.6

>97

1

Pt(0.1)/TiO2(A)

benzene

7.2

6.9

Reaction Mechanism of Aromatic Ring Amination of Benzene and

Recommend Documents