Homogeneous hydrogenation of the –NN–, –CHN–, and –NO<sub>2</sub>groupings

Jardine, I.; McQuillin, F. J.

doi:10.1039/c2970000626a

Cited by 36 publications

(16 citation statements)

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“…The conversions are lower confirming a strong influence of steric and electronic factors, as reported by FishÕs studies [12][13][14][15]. 1 In conclusion, the three complexes (1)- (3) are catalytically active in the hydrogenation of nitrogen containing heterocycles giving results comparable with those reported in the literature for other ruthenium systems like RuCl 2 (CO) 2 (PPh 3 ) 2 and Ru 4 H 4 (CO) 12 , but operating under milder reaction temperatures (353-373 K against 453 K) and lower catalyst/substrate ratio (1/100 against 1/10) [15].…”

Section: Resultsmentioning

confidence: 51%

“…Kinetic analysis of the data reported in Table 1 (entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], following the procedure reported by Frediani et al [8], shows a first partial order with respect to reaction time with all the catalysts tested. The kinetic rates (K c ) are in the following order: (3) ) (2) @ (1) (14.60, 6.37 and 6.36 · 10 À6 s À1 , respectively) ( Table 2).…”

Section: Reaction Timementioning

confidence: 99%

“…The following catalysts were prepared according to the literature and their spectroscopic characteristics were in agreement with the data reported: Ru(CO) 2 -(CH 3 COO) 2 (P n Bu 3 ) 2 [16], Ru(CO) 2 (CH 3 COO) 2 (PPh 3 ) 2 [17], RuH 2 (CO) 2 (P n Bu 3 ) 2 (1) [3], RuH 2 (CO) 2 (PPh 3 ) 2 (2) [5], and RuH 2 (PPh 3 ) 4 (3) [1].…”

Section: Instruments and Materialsmentioning

confidence: 99%

“…Many examples of homogeneous catalytic complexes, mostly based on Rh, Ru, Fe and Co, have been employed after the first application of Jardine and McQuillin for the selective reduction of pyridine to piperidine [1] in the presence of the Rh(py) 3 Cl 3 /NaBH 4 system. The activity and selectivity of several rhodium and ruthenium complexes in different reaction conditions have been studied by various authors [2] and extensive studies on homogeneous hydrogenation of nitrogen containing heterocycles by use of Rh(I) and Ru(II) complexes, such as Rh(PPh 3 ) 3 Cl, Ru(PPh 3 ) 3 HCl and [RhCp*(MeCN) 3 ] 2+ , are due to Fish and co-workers, who also proposed a mechanism for such reactions.…”

Section: Introductionmentioning

confidence: 99%

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Catalytic activity of dihydride ruthenium complexes in the hydrogenation of nitrogen containing heterocycles

Frediani

Pistolesi

Frediani

et al. 2006

Inorganica Chimica Acta

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The catalytic activity of the dihydride ruthenium complexes, RuH 2 (CO) 2 (P n Bu 3 ) 2 , RuH 2 (CO) 2 (PPh 3 ) 2 and RuH 2 (PPh 3 ) 4 , in the hydrogenation of nitrogen containing heterocycles has been tested by analyzing the influence of reaction parameters such as temperature, hydrogen pressure, catalyst concentration, on the rate and regioselectivity of the reaction.RuH 2 (PPh 3 ) 4 shows a better catalytic activity with an 86.7% conversion of quinoline after 24 h at 100°C under a hydrogen pressure of 25 bar, while RuH 2 (CO) 2 (PPh 3 ) 2 and RuH 2 (CO) 2 (P n Bu 3 ) 2 in the same conditions give a conversion of 37.1% and 35.6%, respectively. These results are confirmed by the reaction rate of the hydrogenation of quinoline, since the K c in the presence of RuH 2 (PPh 3 ) 4 (1.46 · 10 À5 s À1 ) is higher than others (6.37 · 10 À6 s À1 for RuH 2 (CO) 2 (PPh 3 ) 2 and 6.36 · 10 À6 s À1 for RuH 2 (CO) 2 (P n Bu 3 ) 2 ).Noteworthy is the selectivity of these catalytic systems in the hydrogenation of quinoline: in all tests the three catalysts lead to 1,2,3,4-tetrahydroquinoline as the major product, furthermore this compound is the only formed in the presence of RuH 2 (CO) 2 (PPh 3 ) 2 . The selectivity is affected by the presence of an acid (CH 3 COOH) or a base (N n Bu 3 ) in the reaction media.The complex RuH 2 (PPh 3 ) 4 is catalytically active, even if in a minor extent, in the hydrogenation of isoquinoline, pyridine and 2-methylpyridine.The basicity of the substrate and steric hindrance around the nitrogen atom show a great influence on the conversion. The results obtained suggest that the catalytic system activates a heterocyclic ring through the coordination of the heteroatom to the metal centre of the complexes.

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Section: Resultsmentioning

confidence: 51%

Section: Reaction Timementioning

confidence: 99%

Section: Instruments and Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Catalytic activity of dihydride ruthenium complexes in the hydrogenation of nitrogen containing heterocycles

Frediani

Pistolesi

Frediani

et al. 2006

Inorganica Chimica Acta

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“…In a previous paper [2], we reported the transfer hydrogenation of organic substrates containing a functional group such as C@C, C@O, N@N or N-N. The catalysts were rhodium complexes with nitrogen containing ligands such as 2,2 0 -bipyridine (bipy), 1,10-phenantroline (phen) or 3,3 0 -dimethoxy-2,2 0 -bipyridine (dmo-bipy) while propan-2-ol was the hydrogen donor. These ligands show very important properties because they chelate the metal through two nitrogen atoms giving complexes having a higher stability than those containing monodentate ligands.…”

Section: Introductionmentioning

confidence: 99%

Quinoline transfer hydrogenation by a rhodium bipyridine catalyst

Frediani

Rosi

Cetarini

et al. 2006

Inorganica Chimica Acta

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Dedicated to celebrate Brian JamesÕs scientific career and 70th birthday. AbstractThe catalytic activity of the rhodium complex cis-[Rh(bipy) 2 Cl 2 ]Cl AE 2H 2 O in the transfer hydrogenation of different unsaturated substrates is reported. This complex, if pre-activated, is very active in the transfer hydrogenation of ketones (i.e., cyclohexanone is reduced with a 38.1% conversion at 283 K and 100% at 313 K) while in the case of hex-1-ene, a 36.8% conversion was reached at 293 K. A cyclic olefin (cyclohexene) was also reduced with a lower, but still significant, conversion.It is interesting to note the catalytic activity of this complex in the transfer hydrogenation of a C@N double bond belonging to imides or nitrogen-containing heterocycles. For instance, N-benzylidenaniline was hydrogenated to N-benzylaniline at 303 K with a conversion of 27.3%. Increasing the temperature to 353 K, the conversion rised to 91.8%. A nitrogen containing heterocycle, quinoline, was also reduced by transfer hydrogenation at 353 K with a 11.7% conversion giving 1,2,3,4-tetrahydroquinoline (selectivity of 96.6%). The conversion rised up to 54.2% with a still high selectivity (84.5%) when the temperature was 383 K. Almost the same activity was shown in the reduction of pyridine to pyperidine (conversion, 51.1% at 383 K), while 2-methylpyridine was hydrogenated with a 24.7% conversion.

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