Recyclable Polymer-Supported Terpyridine

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Apr 7, 2017 - Amides in Water Using NaN3 as Ammonia Equivalent. Toshimasa Suzuka * .... Pd) at 50C for 8 h under 5 atm of CO gas. The reaction mixture ...
catalysts Article

Recyclable Polymer-Supported Terpyridine–Palladium Complex for the Tandem Aminocarbonylation of Aryl Iodides to Primary Amides in Water Using NaN3 as Ammonia Equivalent Toshimasa Suzuka *, Hiromu Sueyoshi and Kazuhito Ogihara Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan; [email protected] (H.S.); [email protected] (K.O.) * Correspondence: [email protected]; Tel.: +81-98-893-8531 Academic Editor: Xiao-Feng Wu Received: 17 March 2017; Accepted: 5 April 2017; Published: 7 April 2017

Abstract: Primary aromatic amides are valuable compounds, which are generally prepared via Beckmann rearrangement of oximes and the hydration of nitriles in organic solvents. We investigated the environmentally friendly catalytic aminocarbonylation in water. Thus, a novel heterogeneous transition-metal catalyst, a polymer-supported terpyridine–palladium(II) complex, was prepared and found to promote azidocarbonylation of aryl iodides with NaN3 and to reduce the generated benzoyl azides in water under CO gas to yield primary aryl amides with high to excellent yield in a one-pot reaction. The catalyst was recovered and reused several times with no loss of catalytic activity. Keywords: aminocarbonylation; azidocarbonylation; palladium; terpyridine; water; sodium azide; carbon monoxide; Staudinger reaction

1. Introduction Primary amides are valuable compounds that are present in several natural products, are important structural motifs in pharmacologically active molecules [1], and are useful in engineering materials such as conductive polymers [2,3]. Although general procedures have been established for their preparation [4–8], e.g., the Beckmann rearrangement of oximes and the hydration of nitriles, there is continuing demand for the development of catalytic, new, improved, effective, and environmentally friendly methodologies for the synthesis of primary amides. Recently, we developed the aminocarbonylation of aryl iodides to form primary amides in water using MeONH2 and a polymer-supported terpyridine–palladium(II) complex as an environmentally friendly synthesis; however, the reported reaction did not yield a high conversion efficiency [9]. Conversely, palladium-catalyzed carbonylation reactions of aromatic halides in the presence of several nucleophiles have undergone rapid development since the pioneering work of Heck and co-workers in 1974 [10]. With regard to the Heck carbonylation reaction, aminocarbonylation reactions have also been developed as an alternative to the preparation of secondary or tertiary amides, as described in [11]. In 2010, Beller and co-workers developed the palladium-catalyzed synthesis of primary amides using carbon monoxide and ammonia [12,13]. This reaction used gaseous ammonia and Pd(OAc)2 /dppf or Pd(OAc)2 /nBuP(1-Adamantyl)2 as the catalytic system. The toxicity of gaseous ammonia is the same as that of carbon monoxide at a threshold limit values of 50 ppm. Therefore, hexamethyldisilazane [14], formamide [15], titanium-nitrogen complexes, ammonium carbamate [16], and methoxyamine [17] have been researched as effective ammonia equivalents for the palladium-catalyzed aminocarbonylation reaction in an organic solvent.

Catalysts 2017, 7, 107; doi:10.3390/catal7040107

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From the the viewpoint viewpoint of of green green chemistry, chemistry, three three principal principal drawbacks drawbacks of of the the reported reported protocol protocol exist exist From despite consideration considerationofof environmental impact andofcost of the reported (1) the despite thethe environmental impact and cost the reported reaction: reaction: (1) the expensive expensive palladium catalyst needs to be disposed of after being used a few times; (2) the products palladium catalyst needs to be disposed of after being used a few times; (2) the products might become might become (3) contaminated; (3) the organic solvent is both expensive and toxic. contaminated; the organic solvent is both expensive and toxic. On the the contrary, contrary, we we recently recently developed developed an an amphiphilic amphiphilic polystyrene–poly(ethylene polystyrene–poly(ethylene glycol) glycol) On (PS–PEG) resin-supported terpyridine–palladium complex as a phosphine-free catalyst and found it (PS–PEG) resin-supported terpyridine–palladium complex as a phosphine-free catalyst and found totobebeeffective aerobic conditions conditions it effectivefor formetal-catalyzed metal-catalyzedreactions reactionsin inwater water under under heterogeneous heterogeneous and and aerobic with high recyclability [18–21]. As an extension of that study, we investigated the catalytic of the with high recyclability [18–21]. As an extension of that study, we investigated the use catalytic PS–PEG–terpyridine–palladium(II) complex for the azidocarbonylation of aryl halides using sodium use of the PS–PEG–terpyridine–palladium(II) complex for the azidocarbonylation of aryl halides azide sodium as anazide ammonium equivalent and and subsequently performed with using as an ammonium equivalent subsequently performedreduction reduction with polymethylhydrosiloxane (PMHS) to produce primary amides in water. Although sodium azide is polymethylhydrosiloxane (PMHS) to produce primary amides in water. Although sodium azide highly toxic, it is ease to handle because it is not gaseous, and it has advantage that it can be handled is highly toxic, it is ease to handle because it is not gaseous, and it has advantage that it can be handled stably in in water. water. There There is is only onlyone onereported reportedexample exampleof ofaaPd/Xantphos Pd/Xantphos catalyzed catalyzed azidocarbonylation azidocarbonylation stably reaction in tetrahydrofuran (THF)-producing benzoyl azide products, and this was not performed performed reaction in tetrahydrofuran (THF)-producing benzoyl azide products, and this was not with the the aim aim of of synthesizing synthesizing primary primary amines amines [22]. [22]. with In this report, complexes of the type [(R 3P)P) 2Pd(Ph)N3] have been reported not to undergo CO In this report, complexes of the type [(R 3 2 Pd(Ph)N3 ] have been reported not to undergo insertion into a Pd–Ph bond under identical to CO insertion into a Pd–Ph bond under identicalreaction reactionconditions conditions due due to to conversion conversion to [(R33P) Xantphos, which which has has wide wide [(R P)22Pd(Ph)NCO] Pd(Ph)NCO] ++N N22[23]; [23];these these problems problems could could be be overcome overcome using using Xantphos, bite angles [24]. We herein report the results of this investigation and demonstrate that the complex bite angles [24]. We herein report the results of this investigation and demonstrate that the complex effectively catalyzes catalyzes the the aminocarbonylation aminocarbonylation of of various various aryl aryl iodides iodides with with carbon carbon monoxide monoxide in in water water effectively 1 3 using aa terpyridine terpyridine ligand ligand having having aa wide wide bite biteangle, angle,NN1 –Pd–N –Pd–N3 (Scheme (Scheme 1). 1). This This catalyst catalyst system system using presents three benefits: (1) it produces neither organic-solvent waste nor metal-contaminated presents three benefits: (1) it produces neither organic-solvent waste nor metal-contaminated waste; waste; (2) itit is is unaffected unaffected by by oxygen oxygen and and moisture; moisture; (3) (3) itit enables enables the the aminocarbonylation aminocarbonylation reaction reaction to to meet meet (2) green chemical requirements. green chemical requirements.

Scheme 1.1. Aminocarbonylation using polymeric polymeric catalyst catalyst 1.1. PS, polystyrene; PEG, Scheme Aminocarbonylation in in water using poly(ethylene glycol). glycol). poly(ethylene

2. Results Results 2. 2.1. 2.1. Coupling Conditions Upon Upon screening screening the the reaction reaction conditions conditions for for the the aminocarbonylation aminocarbonylation in in water water with with the polymeric polymeric palladium found thatthat the reaction efficiency was greatly by simpleby reaction conditions. palladium1,1,wewe found the reaction efficiency was enhanced greatly enhanced simple reaction Firstly, we examined in water accordinginto water the reported procedures Thus, conditions. Firstly, the we aminocarbonylation examined the aminocarbonylation according to the[22]. reported the aminocarbonylations iodobenzene (2a) andofNaN (3) were carried out in water with PMHS as procedures [22]. Thus, theofaminocarbonylations iodobenzene (2a) and NaN 3 (3) were carried out 3 reducing the generated benzoyl in the presencebenzoyl of the polymeric 1 (5 molof%the to in water agent with for PMHS as reducing agentazide for the generated azide incatalyst the presence Pd) at 50 ◦ Ccatalyst for 8 h 1under atm CO mixture was filtered, and the recovered polymeric (5 mol5 % to of Pd) at gas. 50 °CThe forreaction 8 h under 5 atm of CO gas. The reaction mixtureresin was beads were with a small water andwith extracted with EtOAc yieldand benzamide (4a) in filtered, andrinsed the recovered resinportion beads of were rinsed a small portion oftowater extracted with only 13% 1, Table EtOAc to yield yield (Entry benzamide (4a)1). in only 13% yield (Entry 1, Table 1). The scope of suitable bases for the aminocarbonylation in water using catalyst 1 was examined. The potassium carbonate, cesium carbonate, and Et3N produced 9.1%, 17%, and 3.0% yields,

unchanged for this aminocarbonylation, which produced 4a with 43%–53% yields, where the reaction is a one-pot combination of azidocarbonylation and a reduction of generated benzoyl azide with PMHS (Entries 11–16, Table 1). Finally, the highest yield (70%) was obtained when the reaction was performed under simple reaction conditions with 4 equivalents of NaN3 in the presence of 5 mol Catalysts 2017, 7, 1 107 3 of 8 % of catalyst in water at 45 °C for 24 h under 5 atm of CO gas. Table 1. Aminocarbonylation of phenyl iodides with NaN3 using polymeric catalyst 1 in water a. Table 1. Aminocarbonylation of phenyl iodides with NaN3 using polymeric catalyst 1 in water a .

Entry

NaN3 (equiv.)

Base (equiv.)

PMHS (equiv.)

Temp. (◦ C)

Time (h)

Yield of 4a (%)

Entry NaN3 (equiv.) Base (equiv.) PMHS (equiv.) Temp. (° C) Time (h) Yield of 4a (%) 1 2.0 none 7.5 50 8 13 12 2.02.0 none 7.5 50 8 13 K2 CO3 7.5 50 8 9.1 Cs23CO3 23 2.02.0 K2CO 7.5 7.5 50 50 8 8 9.1 17 Et33 N 34 2.02.0 Cs2CO 7.5 7.5 50 50 8 8 17 3.0 5 2.0 Cs2 CO3 7.5 50 24 18 4 2.0 Et3N 7.5 50 8 3.0 6 2.0 none 7.5 50 24 31 57 2.01.0 Cs2CO 3 7.5 7.5 50 50 24 24 18 24 none 68 2.03.0 none 7.5 7.5 50 50 24 24 31 48 none none 79 1.04.0 none 7.5 7.5 50 50 24 24 24 50 none 810 3.05.0 none 7.5 7.5 50 50 24 24 48 46 11 4.0 none 6.0 50 24 48 912 4.04.0 none 7.5 4.5 50 50 24 24 50 43 none 1013 5.04.0 none 7.5 3.0 50 50 24 24 46 50 none 14 4.0 none 0.2 50 24 11 4.0 none 6.0 50 24 48 48 15 4.0 none 0.1 50 24 12 4.0 none 4.5 50 24 43 51 16 4.0 none none 50 24 53 1317 4.04.0 none 3.0none 50 45 24 24 50 70 none 1418 4.04.0 none 0.2none 50 40 24 24 48 66 none 15 4.0 none 0.1 50 24 51 a All reactions were performed with 2a (0.4 mmol), NaN , polymethylhydrosiloxane (PMHS), and polymeric catalyst 3 16 4.0 none none 50 24 53 1 (5 mol %) in H2 O (3.0 mL) under a CO atmosphere. Yields were determined by gas chromatography based on 17 4.0 none none 45 24 70 n-dodecane as an internal standard. 18 4.0 none none 40 24 66 a

All reactions were performed with 2a (0.4 mmol), NaN3, polymethylhydrosiloxane (PMHS), and

The scope of suitable bases for the aminocarbonylation in water using catalyst 1 was examined. polymeric catalyst 1 (5 mol %) in H2O (3.0 mL) under a CO atmosphere. Yields were determined by The potassium carbonate, cesium carbonate, and Et3 N produced 9.1%, 17%, and 3.0% yields, gas chromatography based on n-dodecane as an internal standard. respectively (Entries 2–4, Table 1). Next, we tested prolonged reaction times using Cs2 CO3 , but the did Tolerance not improve as expected (Entry 5, Table 1). In contrast, tripling the time gave a high 2.2. yield Substrate yield when no base was used (Entry 6, Table 1). The amounts of NaN3 and PMHS were investigated With the optimal conditions hand, we examined polymer-supported for the aminocarbonylation in water. in Thus, the reaction was carried out with 1.0–5.0 terpyridine– equivalents palladium-catalyzed aminocarbonylation of several iodoarenes, and the are summarized in of NaN3 to produce benzamide (4a) in 24%, 48%, 50%, and 46% yields, results respectively (Entries 7–10, Table 1). 2. The reaction of 2atowith azide (3) provided thereduced, intendedthe benzamide (4a) inalmost a 70% Table It was surprising findsodium that, even though PMHS was yield remained yield (Entry 1, Table 2), and the reactions with iodobenzene having methyl groups at the ortho-, unchanged for this aminocarbonylation, which produced 4a with 43%–53% yields, where the reaction meta-, andcombination para-positions on the benzene also of afforded (4b), is a one-pot of azidocarbonylation and ring a reduction generated4-methylbenzamide benzoyl azide with PMHS 3-methylbenzamide (4c), and 2-methylbenzamide (4d) 64%, 59%, and yields, (Entries 11–16, Table 1). Finally, the highest yield (70%) wasinobtained when the26% reaction wasrespectively performed (Entries 2–4, Table 2). under simple reaction conditions with 4 equivalents of NaN3 in the presence of 5 mol % of catalyst 1 in water at 45 ◦ C for 24 h under 5 atm of CO gas. 2.2. Substrate Tolerance With the optimal conditions in hand, we examined polymer-supported terpyridine–palladiumcatalyzed aminocarbonylation of several iodoarenes, and the results are summarized in Table 2. The reaction of 2a with sodium azide (3) provided the intended benzamide (4a) in a 70% yield (Entry 1, Table 2), and the reactions with iodobenzene having methyl groups at the ortho-, meta-, and para-positions on the benzene ring also afforded 4-methylbenzamide (4b), 3-methylbenzamide (4c), and 2-methylbenzamide (4d) in 64%, 59%, and 26% yields, respectively (Entries 2–4, Table 2).

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Table 2. Aminocarbonylation of aryl iodides with NaN3 using polymeric catalyst 1 in water a. Table 2. Aminocarbonylation of aryl iodides with NaN3 using polymeric catalyst 1 in water a. Table 2. Aminocarbonylation of aryl iodides with NaN3 using polymeric catalyst 1 in water a .

Entry 2 4 Yield (%) a 1Entry C6H5-I:2 2a C6H5-CONH 70 a a 4 4 2: 4a Yield Entry 2 Yield(%) (%) 2 1 p-MeC 6H4-I: 2b p-MeC 6H4-CONH2: 4b 64 C66H H 2a C6CH6H 70 1 C 5-I: 5-CONH 4a 70 5 -I:2a 5 -CONH 2 :2:4a 3 2 m-MeC m-MeC 6H-CONH 4- CONH:2:4b 4c 59 p-MeC66H H44-I: -I:2c 2b p-MeC 64 6H 4-I: 6H 4 4-CONH 2 2: 4b 2 p-MeC 2b p-MeC 6H 64 4 3 o-MeC 6H4H -I: 2d o-MeC 6H H 4- CONH2:: 4d 26 m-MeC -I: 2c m-MeC 4c 59 4 2c 6 6H 4 4- CONH 2 2: 4c 3 m-MeC66H4-I: m-MeC 59 5 4 1-iodonaphthalene: 1-naphthamide: 4.2 o-MeC H4 -I: 2d2e o-MeC : 4d 26 6H 4 - CONH24e 4 o-MeC66H4-I: 2d o-MeC 6H4- CONH2: 4d 26 1-iodonaphthalene: 1-naphthamide: 4e 4.2 6 5 o-NO2C6H4-I: 2f 2e o-NO 2C6H4-CONH 2: 4f 62 b 5 1-iodonaphthalene: 2e 1-naphthamide: 4e 4.2 o-NO2 C o-NO 6241b b 7 6 p-MeOC 6H 4-I: 2g2f p-MeOC 6H -CONH22:: 4f 4g 6H 4 -I: 2 C6 H 44-CONH 6 o-NO2C6H4-I: 2f o-NO2C6H4-CONH2: 4f 62 7 p-MeOC H -I: 2g p-MeOC H -CONH : 4g 41 8 p-CF3C6H64-I:4 2h p-CF3C66H44-CONH22: 4h 90 78 p-MeOC 6H4-I: 2g p-MeOC 6H4-CONH2: 4g p-CF23CC66HH4-I: p-CF 9041b 4 -I:2i2h 3 C26CH 4 -CONH 2 :2:4h 9 p-NO p-NO 6H 4-CONH 4i 84 b 89 p-CF 3 C 6 H 4 -I: 2h p-CF 3 C 6 H 4 -CONH 2 : 4h 90 p-NO C46-I: H42j-I: 2i p-NO H4-CONH : 4i 8482 2 C66H 4 -CONH 10 p-FC62H p-FC 2:24j 910 p-NO 2 C 6 H 4 -I: 2i p-NO 2 C 6 H 4 -CONH 2 : 4i 84 p-FC6 H4 -I: 2j p-FC6 H4 -CONH2 : 4j 82 b 11 p-ClC6H 4-I: 2k p-ClC6H4-CONH2: 4k 81bb 1011 p-FC66HH4-I: 2j p-FC 6H-CONH 4-CONH:2:4k 4j p-ClC -I: 2k p-ClC H 8182 4 6 4 2 12 p-BrC6H4-I: 2l p-BrC 6H4- CONH2: 4l 65 b 1112 p-ClC 2k p-ClC 6 H 4 -CONH 2 : 4k 81 p-BrC66HH4-I: -I: 2l p-BrC H CONH : 4l 65 4 6 4 2 a All reactions were performed with 2 (0.4 mmol), NaN3 (1.6 mmol), and polymeric catalyst 12 p-BrC6H4-I: 2l p-BrC6H4- CONH2: 4l 65 a All reactions were performed with 2 (0.4 mmol), NaN (1.6 mmol), and polymeric catalyst 1 (5 mol %) in H O (3.0 1a All (5 mol %) in H 2O (3.0 mL) under 5 atm 3 of CO gas. Yields were determined by gas 2 reactions were performed with 2 (0.4 mmol), NaN3 (1.6 mmol), and polymeric catalyst mL) under 5 atm of CO gas. Yields were determined by gas chromatographyb based on n-dodecane as an internal chromatography based on n-dodecane as an internal standard; isolated yield. 1 (5b mol %) in H2O (3.0 mL) under 5 atm of CO gas. Yields were determined by gas standard; isolated yield.

b isolated yield. chromatography on n-dodecane as an internal standard;2d–f The different reactionbased outcome for 2-substituted iodoarenes is hardly surprising because benzoyl azides bearing an ortho substituent are 50–200 times more reactive the because Curtius The surprising The different different reaction reaction outcome outcome for for 2-substituted 2-substituted iodoarenes iodoarenes 2d–f 2d–f is is hardly hardlytoward surprising because rearrangement than their meta and para isomers [25]. Thus, the reaction of 1-iodonaphthalene (2e) benzoyl benzoyl azides azides bearing bearing an an ortho ortho substituent substituent are are 50–200 50–200 times times more more reactive reactive toward toward the the Curtius Curtius occurred under than similar conditions to afford the 1-naphthamide (4e) in a 4.2% yield. rearrangement theirreaction meta and and paraisomers isomers [25].Thus, Thus, reaction of 1-iodonaphthalene rearrangement their meta para [25]. thethe reaction of 1-iodonaphthalene (2e) iodobenzene derivatives 2g–l bearing electron-donating and electron-withdrawing substituents at (2e) occurred under similar reaction conditions affordthe the1-naphthamide 1-naphthamide(4e) (4e)inin 4.2% yield. occurred under similar reaction conditions to to afford aa 4.2% their para-positions produced 4-methoxybenzamide 4-trifluoromethylbenzamide (4h), iodobenzene derivatives 2g–l bearing bearing electron-donating(4g), andelectron-withdrawing electron-withdrawing substituents iodobenzene 2g–l electron-donating and substituents at 4-nitrobenzamide (4i), 4-fluorobenzamide (4j), 4-chlorobenzamide (4k), and 4-bromobenzamide (4l) at their para-positions produced 4-methoxybenzamide (4g), 4-trifluoromethylbenzamide their para-positions produced 4-methoxybenzamide (4g), 4-trifluoromethylbenzamide (4h), in 41%, 90%, 84%, (4i), 82%, 81%, and 65% yields, respectively (Entries(4k), 7–12, Table 2). A substrate having 4-nitrobenzamide (4j), 4-chlorobenzamide and 4-bromobenzamide (4l)(4l) in 4-nitrobenzamide (4i),4-fluorobenzamide 4-fluorobenzamide (4j), 4-chlorobenzamide (4k), and 4-bromobenzamide an electron-withdrawing substituent tended to produce a high yield. 41%, 90%, 84%, 82%, 81%, and 65% yields, respectively (Entries 7–12, Table 2). A substrate having an in 41%, 90%, 84%, 82%, 81%, and 65% yields, respectively (Entries 7–12, Table 2). A substrate having

electron-withdrawing substituent tended to produce a high yield. an electron-withdrawing substituent tended to produce a high yield. 2.3. Recycling Experiments 2.3. Experiments 2.3. Recycling Recycling Experiments of catalyst 1 was examined for the aminocarbonylation of The recyclability The of(2h) catalyst 1 was aminocarbonylation of 4-iodobenzotrifluoride 4-iodobenzotrifluoride NaNexamined 3 (3) (Scheme 2). After the which produced Therecyclability recyclability ofwith catalyst 1 wasfor the examined for first the reaction, aminocarbonylation of (2h) with NaN (3) (Scheme 2). After the first reaction, which produced 4-(trifluoromethyl)benzamide 4-(trifluoromethyl)benzamide (4h) in a 90% yield, the catalyst was recovered by simple filtration, 3 4-iodobenzotrifluoride (2h) with NaN3 (3) (Scheme 2). After the first reaction, which produced (4h) in awith 90% H yield, the catalyst wasinrecovered by simple filtration, dried under washed 2O, dried under (4h) vacuum, and reused fivecatalyst times under similarwith reaction to 2 O,conditions 4-(trifluoromethyl)benzamide a 90% yield, the waswashed recovered byHsimple filtration, vacuum, and reused five times under similar reaction conditions to afford 4h in 88%, 88%, 87%, afford 4h in 88%, 88%, 87%, 88%, and 88% yields. After the recycling experiments, inductively washed with H2O, dried under vacuum, and reused five times under similar reaction conditions to 88%, and 88% yields. After the 88%, recycling inductively coupled experiments, plasma-atomic emission coupled plasma-atomic emission spectrometry analysis showed that the concentration of afford 4h in 88%, 88%, 87%, and experiments, 88% (ICP–AES) yields. After the recycling inductively spectrometry (ICP–AES) analysis showed that the concentration of Pd leached into the aqueous Pd leached into the aqueous solution was