Room Temperature Chemoselective Deoxygenation of Aromatic

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Room Temperature Chemoselective Deoxygenation of Aromatic Ketones and Aldehydes Promoted by a Tandem Pd/TiO + FeCl Catalyst 2

3

Zhenhua Dong, Jinwei Yuan, Yongmei Xiao, Pu Mao, and Wentao Wang J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01667 • Publication Date (Web): 20 Aug 2018 Downloaded from http://pubs.acs.org on August 20, 2018

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The Journal of Organic Chemistry

Room Temperature Chemoselective Deoxygenation of Aromatic Ketones and Aldehydes Promoted by a Tandem Pd/TiO2 + FeCl3 Catalyst Zhenhua Dong,1 Jinwei Yuan,1 Yongmei Xiao,1 Pu Mao,1 Wentao Wang*,2 1

College of Chemistry, Chemical and Environmental Engineering, Henan

University of Technology, Lianhua Street 100, Zhengzhou 450001, China 2

Dalian Institute of Chemical Physics, Chinese Academy of Sciences,

Zhongshan Road 457, Dalian 116023, China

ABSTRACT: A rapid and practical protocol for the chemoselective deoxygenation of various aromatic ketones and aldehydes was described, which used a tandem catalyst composed of heterogeneous Pd/TiO2 + homogeneous

FeCl3

with

the

green

hydrogen

source,

polymethylhydrosiloxane (PMHS). The developed catalytic system was robust and scalable, as exemplified by the deoxygenation of acetophenone, which was performed on a gram scale in atmospheric environment utilizing only 0.4 mol% Pd/TiO2 + 10 mol% FeCl3 catalyst to give the corresponding ethylbenzene in 96% yield within 10 min at 1

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The Journal of Organic Chemistry 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

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room temperature. Furthermore, the Pd/TiO2 catalyst was shown to be recyclable up to three times without an observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. Insights toward the reaction mechanism of Pd-catalyzed reductive deoxygenation for aromatic ketones and aldehydes were investigated through operando IR, NMR, GC-MS techniques. KEYWORDS: green chemistry, deoxygenation reaction, carbonyl compounds, palladium catalysis, polymethylhydrosiloxane. INTRODUCTION Chemoselective deoxygenation reactions continued to attract wide interest in modern organic synthesis because of the fundamental importance of the reaction in the synthesis of biologically active molecules as well as in industrial-scale procedures for the transformation of both biomass feedstocks and petroleum chemicals.1 There was a great demand for the development of new protocols, especially utilizing cheap and environmentally friendly catalysts. To date, many useful manners for the

chemoselective

deoxygenation

of

oxygen-containing

organic

molecules, such as alcohols, aldehydes, ketones, amides, epoxides and nitro compounds, have been developed.2 Conventional methods for the reduction of carbonyl compounds to the corresponding alkanes included the Barton-McCombie (R3SnH),3 NaBH4, borane, Clemmensen (Zn/Hg, HCl) and Wolff-Kishner-Huang (N2H4, KOH) reductions with rigorous 2


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reaction conditions and stoichiometric amounts of unfriendly reagents. Subsequent developments led to mild stoichiometric protocols for the deoxygenation of carbonyl compounds with poor atom economy and undesirable byproduct, in which various metal hydride reagents were employed.4 To address these issues, hydrogen gas was developed for the deoxygenation of carbonyl compounds promoted by transition metal catalysts with H2O being the only byproduct.5 Although H2 was an atom efficient and nontoxic reducing agent, the reaction usually performed at high temperature and pressure with the explosion risk. In contrast, silanes can be considered as one of the most inexpensive and environmentally friendly

hydride

donors.

Of

the

many

available

silanes,

polymethylhydrosiloxane (PMHS), a plentiful and green byproduct of the silicone industry, is a very attractive option.6 In this context, although homogeneous catalytic systems for the deoxygenation of aromatic alcohols, aldehydes, and ketones with PMHS have been developed,7 heterogeneous catalytic systems remain limited.8 Heterogeneous catalysts have remarkable advantages, such as simplified reusability and purification, the potential for incorporation in continuous reactors and microreactors over homogeneous systems, could have great positive environmental consequences.9 Therefore, the development of cheaper, simpler and more efficient heterogeneous catalysts for rapid and chemoselective deoxygenation of aromatic ketones and aldehydes is 3



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highly desirable and challenging. Herein, we report a rapid, practical and efficient method for the chemoselective deoxygenation of various aromatic ketones and aldehydes, using heterogeneous Pd/TiO2 + homogeneous FeCl3 as tandem catalysts together with the green hydride source PMHS. RESULTS AND DISCUSSION Table 1. Optimization of reaction conditions a

entry catalyst

additive

T (oC) t (min) yield(%)b

(mol%)

2a

3a

1

Au/TiO2 (1wt%)

-

40

120

0

11

2

Ru/TiO2 (1wt%)

-

40

120

0

0

3

Pt/TiO2 (1wt%)

-

40

120

0

0

4

Ir/TiO2 (1wt%)

-

40

120

0

0

5

Rh/TiO2 (1wt%)

-

40

120

0

0

6

Pd/TiO2 (1wt%)

-

40

120

5

77

7

Pd/TiO2 (1wt%)

HCl(10)

40

120

53

30

8

Pd/TiO2 (1wt%)

AlCl3 (10)

40

120

83

15

9

Pd/TiO2 (1wt%)

ZrCl4(10)

rt

10

83

9

10

Pd/TiO2 (1wt%)

FeCl3(10)

rt

10

98

2

11

Pd/CeO2 (1wt%)

FeCl3(10)

rt

10

13

42

12

Pd/Al2O3 (1wt%)

FeCl3(10)

rt

10

73

13

13

Pd/FeOx (1wt%)

FeCl3(10)

rt

10

0

0

14

Pd/TiO2 (1wt%)

FeCl3(5)

rt

10

88

9

4


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a

15

Pd/TiO2 (1wt%)

FeCl3(10)

0

10

17

40

16

Pd/TiO2 (1wt%)

FeCl3(10)

50

3

56

22

17

-

FeCl3(10)

rt

120

0

0

The reaction was carried out with 0.4 mol% catalyst, 0.5 mmol

4-methoxyacetophenone 1a, 1.5 mL CH3OH, 90 µL PMHS, room temperature. b

The

GC

yield

was

obtained

from

the

calibration

curve

using

1,3,5-trimethylbenzene as an internal standard.

In initial experiments, we attempted the deoxygenation reaction of 4-methoxyacetophenone (1a) into 4-ethylanisole (2a) with various TiO2 supported metal nanoparticle catalysts. The supported metal catalysts were prepared by a routine deposition precipitation method. During the optimization of the reaction conditions, we found that Pd/TiO2 afforded 5% yield of 4-ethylanisole (2a) in the presence of PMHS (Table 1, entry 6). Other metals such as Au, Ru, Ir, Rh and Pt nanoparticles displayed very low activity (Table 1, entries 1-5). Previous exploratory/mechanistic studies showed that the reaction proceeded in two steps,7,8 where the ketone was first reduced to the alcohol, followed by hydrodeoxygenation to produce the saturated product. On the other hand, metal chloride complexes have been proven to be highly effective Lewis acid catalysts for deoxygenation of alcohols and carbonyl compounds, showing certain stability against moisture and air.10 These features aroused the intriguing question of whether metal chloride salts might be helpful catalysts in hydrogenolytic C-O bond cleavage of the alcohol. And then, various metal chlorides were screened (Table 1, entries 7-10). Among the Lewis 5



acids tested as additives in the reaction, FeCl3 exhibited the highest catalytic activities (Table 1, entry 10). Note that HCl was less active (Table 1, entry 7), arguing that the transformation was primarily catalyzed by Lewis acid (Fe(III)) rather than by Brønsted acid (HCl) from metal chloride hydrolysis. Compared with TiO2, other supports for Pd nanoparticles such as CeO2, FeOx and Al2O3 resulted in low yields of 4-ethylanisole (2a) (Table 1, entries 11-13). Further studies indicated that the efficiency of this transformation decreased when lower catalyst loading was employed (Table 1, entry 14). Different reaction temperatures were investigated. The results showed room temperature provided a desirable yield (Table 1, entry 10 vs entries 15-16). In addition, only a trace amount of the product was detected with FeCl3 or Pd/TiO2 alone which demonstrated the catalytic system had a remarkable synergistic effect on promoting this reaction (Table 1, entry 6 and entry 17). To show the general applicability of the catalytic system, various substrates were tested under the optimized reaction condition. And the results were summarized in Table 2. In general, the catalytic experiments were conducted in the presence of 0.4 mol% Pd/TiO2 and 10 mol% FeCl3 at room temperature with 2-10 min. A variety of aromatic ketones and aldehydes performed well under these conditions. For example, Me, MeO, F substituted acetophenone derivatives reacted smoothly in the presence 6


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of PMHS to give the corresponding alkanes in 85-98% yield (Table 2, entries 1-6). Similar good results were observed on applying long chain aromatic ketones and cyclic ketones (Table 2, entries 7-11), thus demonstrating the versatility of the catalytic system. It is worth noting that heterocyclic ketones such as chroman-4-one (1l) could also be used in this transformation and gave chromane (2l) in 92% yield with 10 min (Table 2, entry 12). Furthermore, various benzaldehydes were also tolerated well, thus giving the desired products in excellent yields (Table 2, entries 13-15). To evaluate the scalability of the present protocol, the deoxygenation of acetophenone (1f) was performed on a gram scale in an open flask setup using 0.4 mol% Pd/TiO2 and 10 mol% FeCl3. Gratifyingly, quantitative deoxygenation of the starting compound was observed after 10 min and the product ethylbenzene (2f) could be isolated in 96% yield (Table 2, entry 16). The deoxygenation of benzophenone by the current catalytic system occurred to give diphenylmethane in 52% yield, presumably because it present too much steric hindrance for the deoxygenation reaction. However, aliphatic ketones are more difficult to be deoxygenated, as exemplified by the reaction of cyclohexanone which resulted in 8% yield of the corresponding alcohol after 2 h and the deoxygenative product cyclohexane was not observed. Table 2. Substrate scope of the chemoselective deoxygenationa

7



O Ar

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H

0.4 mol% Pd/TiO2, 10 mol% FeCl3 R

H R

Ar

PMHS, CH3OH, 2-10 min

2

1

t (min)

yield (%)b

1

10

95

2

10

87

10

85

4

10

98

5

10

95

6

5

98

7

10

91

entry

substrate (1)

product (2)

2b

3 2c

8


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8

10

90

9

10

77

10

85

10

90

10

92

2

99

10

96

10

95

O 10 1j

11 2k O 12 O 1l

O 2l

13 2m

14

O 2n

15 O 2o

9



16c

Page 10 of 26

10

a

96

Unless otherwise noted, the reaction were carried out with 0.5 mmol substrate

(1), 90 µL PMHS, 0.4 mol% Pd/TiO2, 10 mol% FeCl3, 1.5 mL CH3OH, room temperature for 2-10 min. b c

Isolated yields.

The reaction was performed on a 10 mmol scale and resulted in 96% yield of the

isolated product.

To gain insight into the reaction mechanism, several experiments were conducted. Initially, the reactions were monitored using an operando IR spectroscopy. As shown in Figure 1, the kinetic profile clearly shows the peak of the substrate acetophenone at 1679 cm-1 was consumed, a peak of the product ethylbenzene at 2960 cm-1 was accumulated. However, the peaks of the possible intermediates 1-phenylethan-1-ol was not observed obviously. These results indicated that acetophenones were rapidly deoxygenated to the corresponding ethylbenzenes under the standard reaction conditions promoted by Pd nanoparticles wiyh FeCl3. GC-MS and NMR techniques can provide some important details about the intermediates of the reaction. To our delight, a clear spectrum was obtained when the reaction mixture was investigated by GC-MS and NMR analysis. The intermediate 1-phenylethan-1-ol was detected at m/z values of 122.07 (Supporting information S18-S21). Furthermore, 1-phenylethan-1-ol was also detected by NMR spectroscopy (Supporting 10


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information

S17-S18).

These

results

proved

that

intermediate

1-phenylethan-1-ol was involved in the catalytic cycle.

Figure 1. The IR profile of real-time in situ FT-IR spectroscopic analysis of the reductive deoxygenation of acetophenone. The peaks at 1679 cm-1 and 2960 cm-1 correspond to the C=O and benzyl C-H stretching vibrations of acetophenone and ethylbenzene, respectively. A control experiment was also performed to prove the intermediate. As shown in Scheme 1, the substrates 1-phenylethan-1-ol (1p) could be transformed to ethylbenzene (2f) in 5 min under optimized reaction condition. The result further confirmed the reaction intermediate.

11



Scheme 1. Deoxygenation of 1-phenylethan-1-ol under standard conditions. The kinetic reaction results showed that acetophenone was reduced to 1-phenylethan-1-ol within 1 min, which was then further reduced to ethylbenzene

in

the

following

10

min

(Figure

2).

Clearly,

1-phenylethan-1-ol was an intermediate for the deoxygenatve product. This was consistent with the reported proposed ketone-alcohol-alkane reaction pathway.7,8

100

80 Yield (%)

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

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product ketone alcohol

60

40

20

0 0

2

4 6 Reaction time (min)

8

10

Figure 2. Substrate and product concentration profiles as a function 12


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of the reaction time. Reaction conditions: 0.4 mol% Pd/TiO2 catalyst; 10 mol% FeCl3; 0.5 mmol acetophenone 1f; 1.5 mL CH3OH. A hot filtration experiment was carried out to rule out the possible contribution of homogeneous catalysis (Figure 3a). The Pd/TiO2 was separated from the reaction system by filtration at a conversion of 54% for substrate 1f and the filtrate was examined by ICP-AES. The results showed that only a negligible amount of Pd (0.6 ppm corresponding to 0.55wt% of initial charge) were detected in the solution and no further reaction occurred when a new batch of substrates was added into the filtrate. Evidently, the tandem reductive deoxygenation reaction indeed took place on the surface of the solid catalyst. The catalysts also exhibited good recyclability and stability. For example, the catalyst Pd/TiO2 was recovered by simple filtration and reused three times (Figure 3b) without significant loss of catalytic activity. The HRTEM images revealed highly dispersed Pd particles with a mean size of 4.02 nm, for which the narrowly distributed particle sizes range from 3.0 to 5.0 nm owing to the TiO2 stabilization (Figure 4).

13



Figure 3. The hot filtration (a) and reuse experiments (b) of the reaction: 0.5 mmol acetophenone 1f, 0.4 mol% Pd/TiO2, 10 mol% FeCl3, 90 µL PMHS, 1.5 mL CH3OH.

Figure 4. HRTEM images and particle size distribution of Pd/TiO2. Based on the observations noted above, the following reaction 14


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mechanism can be proposed (Scheme 2). The reductive deoxygenation of carbonyl compounds can be divided into two major steps: (i) ketone is reduced to alcohol; (ii) alcohol is hydrodeoxygenated to produce the saturated product. The catalytic cycle begins with the dissociative adsorption of the PMHS onto the Pd nanoparticles surface. The Pd nanoparticles served as the main active sites to activate carbonyl group and adsorb H species in the first step (ketone→alcohol), presumably due to strong affinity of Pd to the carbonyl group. The Lewis acidic FeCl3 would mainly activate the alcohol in the second step (alcohol→aromatic hydrocarbon). With the assistance of FeCl3, the resulting intermediate alcohol undergoes hydrodeoxygenation to give the observed product alkane.

Scheme 2 A plausible reaction mechanism. CONCLUSION In summary, a rapid and relatively environmentally benign method for 15



reductive deoxygenation of aryl ketones and aldehydes has been uncovered using a tandem catalytic system comprised of Pd/TiO2 + FeCl3 under mild conditions in CH3OH. A variety of substrates with several functional groups performed well. The protocol has the advantages of short reaction time (2-10 min), a cheap and green reducing agent (PMHS) together with low loading of a readily available catalyst. Under the optimized reaction conditions, the Pd/TiO2 catalyst is recyclable up to three times without significant loss in activity. The synergistic interplay between supported Pd catalyst and Lewis acid FeCl3 revealed in this work may offer a new guide to the design of other bifunctional catalysts in the green synthesis of fine chemicals. EXPERIMENTAL SECTION General Experimental Information. Aldehydes, ketones, FeCl3, ZrCl4, AlCl3, and polymethylhydrosiloxanen were purchased from Aladdin Industrial Inc. Unless otherwise stated, all reagents were purchased from commercial suppliers and used without further purification. To facilitate the comparison, the metal contents in these catalysts were chosen as 1% by weight. NMR spectra were recorded at room temperature in CDCl3 on 400 MHz spectrometers. HRTEM images were recorded on a JEOL 2100F instrument operating at 120 kV. Prior to HRTEM characterization, the samples were dispersed in CH3CH2OH solution with ultrasonic treatment for 5 min and then dropped onto a 16


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carbon film on copper grid. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) was tested on an IRIS Intrepid II XSP instrument

(Thermo

Electron

Corp.).

Analytical

thin-layer

chromatography (TLC) was performed on silica gel, visualized by irradiation with UV light. For column chromatography, 200-300 mesh silica gel was used. Preparation of Catalysts. 1wt% supported Pd catalysts were prepared by a routine deposition precipitation method. An aqueous solution of H2PdCl4 (0.047 mmol) in 20 mL H2O was heated to 60 oC under vigorous stirring. The pH was adjusted to 8.0 by dropwise addition of NaOH (0.1 M), and then 500 mg of TiO2 was dispersed in the solution. The mixture was stirred for 3 h at 60 oC, after which the suspension was cooled to room temperature. Extensive washing with deionized water was then followed until it was free of chloride ions (determined by silver nitrate solution). Then, the solid was further dried at 80 °C for 12 h. Finally, the sample was reduced at 300 °C under the H2 flow (60 mL•min-1g-1), followed by a passivation process with 1 % (v/v) O2/N2 for 1 h at room temperature. The Pd loading on Pd/TiO2 was determined to be 1.09 wt% by ICP-AES analysis. General Experimental Procedure for the Pd/TiO2 Catalyzed Deoxygenation

of

Ketones

and

Aldehydes.

The

substrate

aldehyde/ketone (0.5 mmol), 0.002 mmol catalyst (based on metal 17



palladium), 0.05 mmol FeCl3 and 1.50 mL CH3OH were sequentially added into a test tube with a magnetic stir bar. The mixture was stirred with 800 rpm stirring speed for 3 min at room temperature. And then PMHS (90 µL, Si-H = 1.32 mmol) was added under stirring. The resulting mixture was stirred at room temperature for 10 min. Upon completion of the reaction, the catalyst was filtrated and washed with CH3OH, dried under air and then directly reused under the same conditions. The solvent was removed under reduced pressure and the residue was purified (if necessary) by flash chromatography using pentane ether/ethyl acetate (10:1) as the eluent to give the corresponding deoxygenated products. All the products were known compounds. The products were confirmed by the comparison of their GC retention time, mass spectrum, and 1H NMR spectrum with the experimental values from National Institute of Standards and Technology (NIST). Table 2, entry 1: Following the general experimental procedure, the reaction mixture of 1a (0.5 mmol, 75.0 mg), Pd/TiO2 (0.4 mol%, 21.2 mg), FeCl3 (10 mol%, 8.0 mg), PMHS (90 uL), was stirred in 1.5 mL CH3OH at room temperature for 10 min to afford 2a (eluent: Pentane ether/ethyl acetate = 10:1) as a colorless oil, 64.6 mg in 95% yield. The structure of the product 2a was confirmed by gas chromatography-mass spectrometer,11 calcd for C9H12O, 136.089, found, 135.962. Table 2, entry 2: 1-ethyl-2-methylbenzene (2b),11 a colorless oil, 52.2 mg 18


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in 87% yield, calcd for C9H12, 120.094, found, 119.961. Table 2, entry 3: 1-ethyl-3-methylbenzene (2c),11 a colorless oil, 51.0 mg in 85% yield, calcd for C9H12, 120.094, found, 119.960. Table 2, entry 4: 1-ethyl-4-methylbenzene (2d),11 a colorless oil, 58.8 mg in 98% yield, calcd for C9H12, 120.094, found, 119.949. Table 2, entry 5: 1-ethyl-4-fluorobenzene (2e),11 a colorless oil, 58.9 mg in 95% yield, calcd for C8H9F, 124.069, found, 123.948. Table 2, entry 6: ethylbenzene (2f),11 a colorless oil, 52.0 mg in 98% yield, calcd for C8H10, 106.078, found, 105.972. Table 2, entry 7: propylbenzene (2g),11 a colorless oil, 54.6 mg in 91% yield, calcd for C9H12, 120.094, found, 119.967. Table 2, entry 8: butylbenzene (2h),11 a colorless oil, 60.3 mg in 90% yield, calcd for C10H14, 134.110, found, 133.977. Table 2, entry 9: pentylbenzene (2i),11 a colorless oil, 57.0 mg in 77% yield, calcd for C11H16, 148.125, found, 148.016. Table 2, entry 10: 2,3-dihydro-1H-indene (2j),11 a colorless oil, 50.2 mg in 85% yield, calcd for C9H10, 118.078; found, 117.984. Table 2, entry 11: 1,2,3,4-tetrahydronaphthalene (2k),11 a colorless oil, 59.4 mg in 90% yield, calcd for C10H12, 132.094; found, 131.943. Table 2, entry 12: chromane (2l),11 a white solid, 61.6 mg in 92% yield, calcd for C9H10O, 134.073; found, 133.924. Table 2, entry 13: toluene (2m),11 a colorless oil, 45.5 mg in 99% yield, 19



calcd for C7H8, 92.063; found, 91.009. Table 2, entry 14: 1-methoxy-2-methylbenzene (2n),11 a colorless oil, 58.6 mg in 96% yield, calcd for C8H10O, 122.073; found, 121.880. Table 2, entry 15: 1-methoxy-3-methylbenzene (2o),11 a colorless oil, 58.0 mg in 95% yield, calcd for C8H10O, 122.073; found, 121.913.

ASSOCIATED CONTENT Supporting Information Characterization of the obtained deoxygenated products, 13CNMR results of the reaction liquid mixture after acetophenone performed 1 and 4 min under the optimized conditions, GC-MS results of the reaction liquid mixture after the substrate acetophenone proceeded 1 min under the optimized conditions, these materials are available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENT

The authors are grateful to the National Natural Science Foundation of China (Project No.21672210) for financial support. This work was generously supported by The Science and Technology Foundation of 20


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Henan Province (No.172102310043), The Colleges and Universities Key

Research

Program

Foundation

of

Henan

Province

(No.17A150007), Doctor Fund of Henan University of Technology (No.2015BS013). REFERENCES (1) (a) Zhou, C. H.; Beltramini, J. N.; Fan, Y. X.; Lu, G. Q. Chemoselective Catalytic Conversion of Glycerol as a Biorenewable Source to Valuable Commodity Chemicals. Chem. Soc. Rev. 2008, 37, 527-549; (b) Bozell, J. J.; Petersen, G. R. Technology Development for the Production of Biobased Products from Biorefinery Carbohydrates-the US Department of Energy's “Top 10” Revisited. Green Chem. 2010, 12, 539-554; (c) Vennestrøm, P. N. R.; Osmundsen,C. M.; Christensen, C. H.; Taarning, E. Beyond Petrochemicals: the Renewable Chemicals Industry. Angew. Chem. Int. Ed. 2011, 50, 10502-10509; (d) Ruppert, A. M.; Weinberg,

K;

Palkovits

R.

Hydrogenolysis

Goes

Bio:

From

Carbohydrates and Sugar Alcohols to Platform Chemicals. Angew. Chem. Int. Ed. 2012, 51, 2564-2601; (e) Alonso, D. M.; Wettstein, S. G.; Dumesic, J. A. Bimetallic Catalysts for Upgrading of Biomass to Fuels and Chemicals. Chem. Soc. Rev. 2012, 41, 8075-8098; (f) Sheldon, R. A. Green and Sustainable Manufacture of Chemicals from Biomass: State of the Art. Green Chem. 2017, 16, 950-963; (g) Baumann, K.; Knapp, H.; Strnadt, G.; Schulz, G.; Grassberger, M. A. Carbonyl to Methylene 21



Page 22 of 26

Conversions at the Tricarbonyl-portion of Ascomycin Derivatives. Tetrahedron Lett. 1999, 40, 7761-7764; (h) Piontek, A.; Bisz, E.; Szostak, M. Iron-Catalyzed Cross-Coupling in the Synthesis of Pharmaceuticals: In

Pursuit

of

Sustainability.

Angew.

Chem.

Int.

Ed.

10.1002/anie.201800364. (2) (a) Li, Z.; Deng, G.; Li, Y. C. Zinc(II) Iodide-Triethylsilane: A Novel Mild Reduction System for Direct Deoxygenation of Aryl Aldehydes, Ketones, and α,β-Unsaturated Enones. Synlett 2008, 19, 3053-3057; (b) Zhou, S. L.; Junge K.; Addis, D.; Das, S.; Beller, M. A Convenient and General Iron-Catalyzed Reduction of Amides to Amines. Angew. Chem. Int . Ed. 2009, 48, 9507-9510; (c) Hanada, S.; Tsutsumi, E.; Motoyama, Y.; Nagashima, H. Practical Access to Amines by Platinum-Catalyzed Reduction of Carboxamides with Hydrosilanes: Synergy of Dual Si-H Groups Leads to High Efficiency and Selectivity. J. Am. Chem. Soc. 2009, 131, 15032-15040; (d) Das, S.; Addis, D.; Zhou, S. L.; Junge, K.; Beller, M. Zinc-Catalyzed Reduction of Amides: Unprecedented Selectivity and Functional Group Tolerance. J. Am. Chem. Soc. 2010, 132, 1770-1771; (e) Mamillapalli, N. C.; Sekar, G. Chemoselective Reductive Deoxygenation and Reduction of α-Keto Amides by Using a Palladium Catalyst. Adv. Synth. Catal. 2015, 357, 3273-3283; (f) Sousa, S. C. A.; Fernandes, T. A.; Fernandes, A. C. Highly Efficient Deoxygenation of Aryl Ketones to Arylalkanes Catalyzed by Dioxidomolybdenum Complexes. Eur. J. Org. 22


Page 23 of 26 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


Chem. 2016, 3109-3112; (g) Schafer, C.; Ellstrom, C. J.; Torok, B. Pd/C-Al-water Facilitated Selective Reduction of a Broad Variety of Functional Groups. Green Chem. 2017, 19, 1230-1234; (h) Dai, X. J.; Li, C. J. En Route to a Practical Primary Alcohol Deoxygenation. J. Am. Chem. Soc. 2016, 138, 5433-5440; (i) O.Bauer, J.; Chakraborty, S.; Milstein, D. Manganese-Catalyzed Direct Deoxygenation of Primary Alcohols. ACS Catal. 2017, 7, 4462-4466. (3) Clive, D. L. J.; Wang, J. A tin Hydride Designed to Facilitate Removal of Tin Species from Products of Stannane-mediated Radical Reactions. J. Org. Chem. 2002, 67, 1192-1198. (4) Lau, C. K.; Dufresne, C.; Belanger, P. C.; Pietre, S.; Scheigetz, J. Reductive Deoxygenation of Aryl Aldehydes and Ketones by Tert-butylamine Borane and Aluminium Chloride. J. Org. Chem. 1986, 51, 3038-3043. (5) (a) Xu, X.; Li, Y.; Gong, Y.; Zhang, P.; Li, H.; Wang, Y. Synthesis of Palladium Nanoparticles Supported on Mesoporous N-Doped Carbon and Their Catalytic Ability for Biofuel Upgrade. J. Am. Chem. Soc. 2012, 134, 16987-16990; (b) Stein, M.; Breit, B. Catalytic Hydrogenation of Amides to Amines under Mild Conditions. Angew. Chem. Int. Ed. 2013, 52, 2231-2234; (c) Guyon, C.; Baron, M.; Lemaire, M.; Popowycz, F.; Metay, E.

Commutative

Reduction

of

Aromatic

Ketones

to

Arylmethylenes/Alcohols by Hypophosphites Catalyzed by Pd/C under 23



Page 24 of 26

Biphasic Conditions. Tetrahedron, 2014, 70, 2088-2095; (d) Kalutharage, N.; Yi, C. S. Scope and Mechanistic Analysis for Chemoselective Hydrogenolysis of Carbonyl Compounds Catalyzed by a Cationic Ruthenium Hydride Complex with a Tunable Phenol Ligand. J. Am. Chem. Soc. 2015, 137, 11105-11114; (e) Li, M. M.; Deng, J.; Lan, Y. K.; Wang, Y. Efficient Catalytic Hydrodeoxygenation of Aromatic Carbonyls over a Nitrogen-Doped Hierarchical Porous Carbon Supported Nickel Catalyst. ChemistrySelect 2017, 2, 8486-8492. (6)

(a)

Lawrence,

N.

J.;

Drew,

M.

D.;

Bushell,

S.

M.

Polymethylhydrosiloxane: a Versatile Reducing Agent for Organic Synthesis. J. Chem. Soc. Perkin Trans. 1 1999, 3381-3391; (b) Chandrasekhar, S.; Chandrasekhar, G.; Babu, B. N.; Vijeender, K.; Reddy, K. V. Reductive Etherification of Carbonyl Compounds with Alkyl Trimethylsilylethers

Using

Polymethylhydrosiloxane

(PMHS)

and

Catalytic B(C6F5)3. Tetrahedron Lett. 2004, 45, 5497-5499; (c) Senapati, K. K. Polymethylhydrosiloxane (PMHS). Synlett 2005, 1960-1961; (d) Addis, D.; Das, S.; Junge K.; Beller, M. Selective Reduction of Carboxylic Acid Derivatives by Catalytic Hydrosilylation. Angew. Chem. Int. Ed. 2011, 50, 6004-6011; (e) Dohlert, P.; Enthaler, S. Conversion of Poly(methylhydrosiloxane) Waste to Useful Commodities. Catal. Lett. 2016, 146, 345-352. (7) (a) Rahaim, R. J. Jr.; Maleczka, R. E. Jr. C-O Hydrogenolysis 24


Page 25 of 26 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


Catalyzed by Pd-PMHS Nanoparticles in the Company of Chloroarenes. Org. Lett. 2011, 13, 584-587; (b) Wang, H.; Li, L.; Bai, X. F.; Shang, J. Y.; Yang, K. F.; Xu, L.W. Efficient Palladium-Catalyzed CO Hydrogenolysis of

Benzylic

Alcohols

and

Aromatic

Ketones

with

Polymethylhydrosiloxane. Adv. Synth. Catal. 2013, 355, 341-347; (c) Gong, S. W.; He, H. F.; Zhao, C. Q.; Liu, L. J.; Cui, Q. X. Convenient Deoxygenation of Aromatic Ketones by Silica-supported Chirosan Schifff Base Palladium Catalyst. Syn. Commu. 2012, 42, 574-581; (d) Zotto, C. D.; Virieux, D.; Campagne, J. M. FeCl3-Catalyzed Reduction of Ketones and Aldehydes to Alkane Compounds. Synlett 2009, 2, 276-278; (e) Lucas, K. M.; Kleman, A. F.; Sadergaski, L. R.; Jolly, C. L.; Bollinger, B. S.; Mackesey, B. L.; McGrath, N. A. Versatile, Mild, and Selective Reduction of Various Carbonyl Groups Using an Electron-deficient Boron Catalyst. Org. Biomol. Chem. 2016, 14, 5774-5778; (f) Ding, G. N.; Li, C. J.; Shen, Y. F.; Lu, B.; Zhang, Z. G.; Xie, X. M. Potassium Hydroxide-Catalyzed Chemoselective Reduction of Cyclic Imides with Hydrosilanes: Synthesis of ω-Hydroxylactams and Lactams. Adv. Synth. Catal. 2016, 358, 1241-1250; (g) Mehta, M.; Holthausen, M. H.; Mallov, I.; Perez, M.; Qu, Z. W.; Grimme, S.; Stephan, D. W. Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations. Angew. Chem. Int. Ed. 2015, 54, 8250-8254. (8) Volkov, A.; Gustafson, K. P. J.; Tai, C. W.; Verho, O.; Backvall, J. E.; 25



Page 26 of 26

Adolfsson, H. Mild Deoxygenation of Aromatic Ketones and Aldehydes over Pd/C Using Polymethylhydrosiloxane as the Reducing Agent. Angew. Chem. Int. Ed. 2015, 54, 5122-5126. (9) (a) Astruc, D.; Lu, F.; Aranzaes, J. R. Nanoparticles as Recyclable Catalysts: the Frontier between Homogeneous and Heterogeneous Catalysis. Angew. Chem. Int. Ed. 2005, 44, 7852-7872; (b) Molnar, A.; Papp, A. Catalyst Recycling-A Survey of Recent Progress and Current Status. Coordin. Chem. Rev. 2017, 349, 1-65. (10) (a) Wang, J. L.; Huang, W.; Zhang, Z. X.; Xiang, X.; Liu, R. T.; Zhou, X. G. FeCl3·6H2O Catalyzed Disproportionation of Allylic Alcohols and Selective Allylic Reduction of Allylic Alcohols and Their Derivatives with Benzyl Alcohol. J. Org. Chem. 2009, 74, 3299-3304; (b) Egi, M.; Kawai, T.; Umemura, M.; Akai, S. Heteropolyacid-Catalyzed Direct Deoxygenation of Propargyl and Allyl Alcohols. J. Org. Chem. 2012, 77, 7092-7097; (c) Bisz, E.; Szostak, M. Iron-Catalyzed C-O Bond Activation: Opportunity for Sustainable Catalysis. ChemSusChem 2017, 10, 3964-3981. (11) The mass spectra of the products were in agreement with the experimental

values

from

NIST

(see

supporting

https://webbook.nist.gov/chemistry/

26


information).

Room Temperature Chemoselective Deoxygenation of Aromatic

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