|Hydrogenation of benzylcyanide to phenetylamines|
Hi I’m working with the hydrogenation of some benzylcyanide to the phenetylamines (made from the red. Of the aldehyde with NaBH4 in MeOH, sub of oh with PBr3 in ether and sub of the bromine with cyanide via NaCN in DMF (ill write a synth. later)
All these reaction work good. But the hydrogenation is quite time consuming. Right now I’m hydrogenate at 6 bars with Pd/C and use 10% hydrochloric acid(aq) in ethanol. It work’s but hydrogenation of 5g takes 1-2dayes. Anyone with experience with other solvent systems??
|Re: Hydrogenation of benzylcyanide|
SWIM experience hydrogenating mostly chloroephedrine to meth, using methanol as the solvent and Pd. 10%/C. SWIM found that many times the catalyst gets poisoned , although it will hydrogenate but slow , so it’s best to change your catalyst 2-3 times until it kicks and you see it taking hydrogens at a good rate so you can be done in less than and hour. At a good rate the hydrogen gets consumed so fast that at the end your bottle is very hot from the reaction ........java
Edit :see also Patent US3458576 originally provided by polysam, then Roger2003 , and recently reviewed by Aurelius
Post 439559 (Aurelius: "US Patent 3458576 reduction of phenylnitropropene", Methods Discourse)
We're all in this world together,
(Rated as: excellent)
Ups, the hydrogen flas was not turned off, that's why no presuredrop was seen. Here is the writup
(To Rhodium, iff you wan't a HTML I mail you one)
From aldehyde to alcohol
50g(0,28mol) 3,4,5-trimethoxybensaldehyde was dissolved into 600mL 0°C methanol (ice bad) under stirring. Then 10g NaBH4 was added in 3 portions, the reaction was left over night.
The next day most of the methanol was removed (rotorvap, important to get a nice extraction)) and the rest diluted with water (500mL) and made acid with 37% HCl(aq). The water was extracted with 4*100mL CH2Cl2, the organic phases was combined, dried and concentrated on the rotor vapor.
Yield 47,2g(93%) 3,4,5-trimethoxybenzylakohol.
Rf (40% EtOAc in Heptane) 0,27
From alcohol to bromide
47,2g(0,24mol) 3,4,5-trimethoxybenzaldehyde was dissolved into 1L ether at 0°C (ice bad) under stirring. Then 25g(0,1mol) PBr3 was added over 30min, the ice removed and the reaction left for 60 min. After that the mixture was poured out into 300mL water, the organic phase was separated, the water extracted with 2*100mL ether, the ether phases combined, washed with 2*50mL water, dried and concentrated (rot. vap.)
Yield 55g(88%) 3,4,5-trimethoxybenzylbromice
Rf (50% EtOAc in Heptane) 0,63
From bromide to nitile
50g(0,19mol) 3,4,5-trimethoxybenzylbromide was dissolved into 600mL DMF under stirring at 0°C (ice bad), then 20g NaCN vas added and the ice bad removed. After 1 hour the mixture was poured out into 2L water, the water was extracted with 4*100mL CH2Cl2. The organic phases was combined, washed with 2*100mL water, dried and concentrated.
Yield of 3,4,5-trimethoxybenzylcyanide 36g(90%)
Rf (50% EtOAc in heptane) 0,45
From nitrile to ammine
Yield 13,7g mescaline freebase.
Phenethylamines via Mandelonitrile Carbamates
(Rated as: excellent)
I have two questions:
- What is your setup to contain 6 bar of pressure? Is there any way to do it for a kitchen chemist, without Parr Apparatus?
- For EveryknowledgableBee:
This is the hydrogenation of a mandelonitrile intermediate to the PEA, at RPT condition, is there any reason that it could not work on a normal phenylacetonitrile, or is this only applicable to O-Ethoxycarbonyl mandelonitriles? Otherwise it would bee a very convenient way to PEA from acetonitrile derivates.
Synthesis of meta-Methoxyphenethylamine via O-(Ethoxycarbonyl)-3-Methoxy-Mandelonitr
J. Org. Chem. 47, 2638-2643 (1982) (../rhodium/pdf /mandelonitri
This is the original reference for the KrZ way to 2C-H (../rhodium/chemistry /2cb.ma
Attempted preparation of 2-(m-methoxyphenyl)ethylamine (4) by reduction of nitrostyrene 6 with lithium aluminum hydride1 gave a product containing a persistent impurity which could be eliminated only if nitrostyrene 6 was rigorously purified. Catalytic hydrogenation2 of 6 gave variable results as the scale was increased. However, an efficient and convenient synthesis of phenylethylamine 4, independent of scale, proceeded in high yield from m-anisaldehyde (5) by first treatment with potassium cyanide and ethyl chloroformate to form O-(ethoxycarbonyl)-3-methoxymandelonitri
To a stirred solution of 13.6 g (0.1 mol) of m-anisaldehyde (5) and 11.9 g (0.11 mol, 10.8 mL) of ethyl chloroformate in 20 mL of THF, cooled in an ice-water bath, was added in one portion 7.2 g (0.11 mol) of KCN dissolved in 25 mL of water. The reaction mixture was stirred for 4 h at 5°C and then slowly warmed to room temperature overnight. Water (100 mL) was added, the aqueous solution was extracted with 3x40 mL of ether, the combined extracts were dried and evaporated, and the residue was distilled to afford 21.4 g (0.92 mol, 92%) of the cyanohydrin carbamate 7: bp 110-115°C/0.3mmHg [lit. bp 132°C/0.4 mmHg].
A solution of 23.5 g (0.1 mol) of 7 in 300 mL of absolute ethanol was added dropwise (0.5 drop/s) to a mechanically stirred solution of 300 mL of absolute ethanol containing 1.5 g of 10% Pd/C catalyst and 12.9g (0.13 mol, 7 mL) of concentrated sulfuric acid as hydrogen was bubbled through the solution. After the addition, stirring and bubbling were continued for 8 h, the reaction mixture was filtered, the filtrate was evaporated, water (100 mL) was added, and the cooled aqueous solution was made alkaline with 4 M sodium hydroxide. The solution was extracted with 4x50 mL of ether, the combined extracts were dried and evaporated, and the residue was distilled to afford 13.9 g (0.09 mol, 92%) of phenylethylamine 4: bp 93-95°C/0.1mmHg [lit. bp 122-123°C/1.0mmHg].
 J. Chem. Soc. C, 2632 (1971)
 Synth. Commun. 1, 47 (1971) and references cited therein. Post 472313 (Rhodium: "Catalytic Hydrogenation of Nitrostyrenes", Serious Chemistry)
 J. Am. Chem. Soc. 55, 2593 (1933) Post 471993 (Rhodium: "Catalytic Reduction of Mandelonitriles", Serious Chemistry)
 Justus Liebig's Ann. Chem. 564, 49 (1949) Post 485823 (Rhodium: "Kindler: Phenylacetonitriles to Phenethylamines", Serious Chemistry)
It was done in a Parr apparatus.
|I have had similar problems.|
I have had similar problems. You get the aldehyde as a byproduct by hydrolysis of the imine.
(Rated as: good read)
Now the hydrogenation is also done witj RaNi. Works as greath as Pd/C
5g 3,4,5-trimethoxybenzonitril was disolved into 100mL ethanol, 20mL 25% ammonia in wather and 1g RaNi was added, the reaction was the hydrogenated at 6 bar for 12 houres, filtrated, evaporated, disolved into 2M HCl(aq), ekstracted with DCM, made basic with NaOH(s), ekstracted with 2*50mL DCM. The organic phases was combined, dryeat and evaporated. Yeald 83%.
That's good .
Hest, if you have the time and enough catalyst/nitrile, could you try the hydrogenation at atmospheric pressure, with a bigger amount of Pd/C, like one gram for 15g nitrile?
To see if bees without Parr apparatus have some hope in that reduction...
Catalytic Reduction of Mandelonitriles
(Rated as: excellent)
This is Reference #3 from Post 448639 (Chimimanie: "Phenethylamines via Mandelonitrile Carbamates", Serious Chemistry):
Catalytic Reduction of Mandelonitriles
By J. S. Buck
J. Am. Chem. Soc. 55, 2593-97 (1933)
In an attempt to simplify the preparation of ß-phenylethylamines, the catalytic reduction of mandelonitriles was investigated. Some previous work in this direction has been cited by Hartung1. Little seems to have been done at moderate pressures and at room temperature. Kindler2 reports that the reaction fails, and3 that acylated nitriles reduce badly, giving poor yields of the ß-phenylethylamines. Paal and Gerum4, in earlier work, reduced mandelonitrile, using palladium, to benzyl alcohol, benzylamine, dibenzylamine and ammonia.
Hartung1 gave details for the reduction of mandelonitrile to ß-phenylethylamine and noted the non-production of ß-hydroxy-ß-phenylethylamine. He used palladium charcoal as catalyst and alcoholic hydrogen chloride as solvent. The Adams catalyst (platinum oxide) and the usual apparatus (Burgess-Parr) offer a simple and expedient method of reduction and were used by the present author to reduce a number of mandelonitriles. In the presence of a slight excess of concentrated hydrochloric acid, the nitrile, in alcoholic solution, is smoothly reduced to the corresponding ß-phenylethylamine or ß-hydroxy-ß-phenylethylamine, which one being determined by the starting material. The reaction is complex, and attention was directed solely to the isolation, as hydrochloride, of the amine. Although some of the yields are not altogether satisfactory, the expediency of the method makes it convenient for the preparation of certain of the ß-phenylethylamines. Of the nitriles examined, those with ortho substituents gave the ß-hydroxy-ß-phenylethylamine, the others giving the ß-phenylethylamine. No meta-substituted nitriles were prepared in a state of sufficient purity for reduction. Kindler5 has recently discussed the mechanism of the production of amines by reduction.
Three carbethoxymandelonitriles and one carbomethoxymandelonitrile were also reduced under the conditions given above. All four gave the corresponding ß-phenylethylamines, showing, in the case of the o-chloro compounds at any rate, that more than a simple hydrolysis is involved, since the non-acylated and the acylated mandelonitriles give different products.
The p-nitrobenzoyl derivatives were prepared for the better characterizing of the amines, particularly as the melting points of the hydrochlorides are not always sharp.
The general method used was to dissolve 0.05 mole of the nitrile or acylated nitrile in 45 mL of alcohol, and after adding 5.0 mL of concentrated hydrochloric acid (1.2 moles) to reduce the solution, at room temperature, with platinum oxide and hydrogen. The initial pressure was 50 lb. The amount of catalyst used was between 0.3 and 1.0 g., the larger amount being used on the slower reductions. The time required for reduction was usually two hours or less, but occasionally eight to ten hours were necessary. The theoretical amount of hydrogen was rarely taken up, the reduction usually stopping considerably short of the end-point. It is essential that the starting material be pure.
The reaction mixtures were worked up by filtering off the catalyst and evaporating the filtrate to dryness under reduced pressure. The residue was then dissolved in absolute alcohol and absolute ether added to incipient precipitation. On standing in the cold the hydrochloride crystallized out and was filtered off, washed with ether, and dried in vacuo. The yields are recorded for material of this purity. There is considerable loss on subsequent recrystallizations owing to the unselective nature of the solvent used (alcohol-ether mixture). For practical purposes, it would be preferable, in most cases, to isolate the free amine directly from the reduction mixture.
For identification, the product was repeatedly recrystallized from alcohol-ether mixture, or in some cases from alcohol, until pure. The hydrochloride was analyzed and converted into the p-nitrobenzoyl derivative of the amine, which was also analyzed. In a number of cases comparison was made with authentic compounds and mixed melting point determinations carried out. The validity of the latter method is sometimes open to doubt when used with hydrochlorides as some of these have unsharp melting points (e. g., homoanisylamine hydrochloride).
Three methods were used to prepare the nitriles. As a rule, the nitrile is only obtainable in quantity by one of the techniques, which is selected by trial.
(1) A method similar to that of McCombie and Parry6 was employed, but, although occasionally giving good yields of pure material, it was erratic.
(2) Anhydrous hydrogen cyanide, in the presence of calcium oxide, was used, after the method of Bigelow, Jenkins and Buck7.
(3) The bisulfite compound of the aldehyde was treated with potassium cyanide solution, in a manner similar to that of Kostanecki and Lampe8.
In all cases the crude product was extracted with ether, and washed (each washing being repeated once) with water, sodium bisulfite solution, water, sodium bicarbonate solution, and finally water. The ether solution was then dried over anhydrous sodium sulfate and the ether removed as completely as possible under reduced pressure at 25-30°C. The resultant oil solidified on standing in the refrigerator and the solid was then ground with petroleum ether (bp 30-60°C), filtered off, washed with petroleum ether and recrystallized from ether-petroleum ether mixture. So obtained, the nitriles are mostly fairly stable and reduce readily. As a rule, the nitriles are very soluble in the usual solvents and very or moderately soluble in ether. In petroleum ether, they are rather slightly soluble.
Table I: Mandelonitriles
a Mentioned but not described by Pictet and Gams9 and Kindler10. In addition to the above, p-dimethylaminomandelonitrile No. 7 and mandelonitrile No. 8 were both prepared by Method 2.
Reduction of Carbethoxy- and Carbomethoxymandelonitriles
Carbethoxymandelonitrile was prepared by the method of Francis and Davis11 and the other three compounds were obtained by practically the same procedure. The reduction was carried out in a manner similar to that of the mandelonitriles, and it proceeded in much the same way as with the non-acylated compounds. The products were isolated and identified in the manner already described. The following results were obtained; carbomethoxymandelonitrile gave ß-phenylethylamine hydrochloride in 38% yield; carbethoxymandelonitrile gave ß-phenylethylamine hydrochloride in 47% yield; o-chlorocarbethoxymandelonitrile gave o-chloro-ß-phenylethylamine hydrochloride in 94% yield, and p-methoxycarbethoxymandelonitrile gave homoanisylamine hydrochloride in 49% yield.
Carbethoxymandelonitrile11 was also used (No. 12). The odors are very faint (nitrile). Except for the p-methoxy compound, the nitriles are practically colorless. They are rather viscous liquids, insoluble in water but miscible with the usual solvents. They are sparingly soluble in petroleum ether, and are quite stable.
Table II: Carbomethoxy- and Carbethoxymandelonitriles
Benzoyl- and p-Nitrobenzoyl Derivatives
The method of preparation was usually to reflux the hydrochloride of the amine with twice its weight of p-nitrobenzoyl chloride and twenty times its weight of benzene for thirty minutes. The benzene was then allowed to boil off and the residue heated on the water-bath for a further forty-five minutes. It was dissolved in warm benzene, shaken with dilute potassium hydroxide solution, and then washed with water. At this point the product usually crystallized out from the benzene and was filtered off, washed with water and recrystallized from alcohol, to which a little water was added. Benzoyl p-dimethylamino-ß-phenylethylamine and benzoyl p-chloro-ß-phenylethylamine were prepared by the Schotten-Baumann method, on account of difficulties encountered with the above method. The solubilities of the compounds are very similar. They are readily soluble in warm alcohol, but separate well on adding a little water to the solutions. They are soluble in warm chloroform, fairly soluble in warm benzene, and sparingly soluble in ether. The compounds are difficult to analyze and require slow burning. The ß-hydroxy group is not nitrobenzoylated by the above procedure.
Table III: Hydrochlorides Of ß-Phenylethylamines And ß-Hydroxy-ß-Phenylethylamines
a Checked by mixed melting point determinations with authentic specimens.
1. A number of mandelonitriles have been prepared in pure crystalline condition and reduced by the Adams method to ß-hydroxy-ß-phenylethylamines or to ß-phenylethylamines, the product being determined by the substituents in the nitrile.
2. The p-nitrobenzoyl or benzoyl derivatives of the amines have been prepared.
3. Several carbethoxy- or carbomethoxymandelonitriles have been similarly reduced to the ß-phenylethylamines.
4. A number of the compounds have not been previously described.
5. Owing to its simplicity and expediency, the reduction described offers a convenient method for the preparation of certain ß-phenylethylamines.
(1) Hartung, J. Am. Chem. Soc., 50, 3370 (1928) Post 450229 (Rhodium: "Catalytic Reduction of Nitriles and Oximes", Methods Discourse)
(2) Kindler, Arch. Pharm., 265, 389 (1927)
(3) Kindler, Arch. Pharm., 269, 70 (1931)
(4) Paal and Gerum, Ber., 42, 1558 (1909)
(5) Kindler, Ann., 485, 113 (1931) Post 485823 (Rhodium: "Kindler: Phenylacetonitriles to Phenethylamines", Serious Chemistry)
(6) McCombie and Parry, J. Chem. Soc., 95, 586 (1909)
(7) Bigelow, Jenkins and Buck, J. Am. Chem. Soc., 52, 5201 (1930)
(8) Kostanecki and Lampe, Ber., 42, 828 (1909); cf. Patent DE85230
(9) Pictet and Gams, Ber., 42, 2943 (1909)
(10) Kindler and Peschke, Arch. Pharm., 269, 581 (1931)
(11) Francis and Davis, J. Chem. Soc., 95, 1409 (1909)
(12) Described as oily by Braun and Blessing, Ber., 56, 2153 (1923)
Catalytic Hydrogenation of Nitrostyrenes
(Rated as: excellent)
This is Reference #2 from Post 448639 (Chimimanie: "Phenethylamines via Mandelonitrile Carbamates", Serious Chemistry):
ß-Phenethylamines. The Catalytic Hydrogenation of omega-Nitrostyrenes
D. P. Wagner, A. I. Rachlin, and S. Teitel
Synthetic Communications 1(1), 47-50 (1971) (../rhodium/chemistry /ns2pea
Good yields of ß-phenethylamine hydrochloride salts are obtained directly from the catalytic reduction of conjugated nitroalkenes in dilute hydrochloric acid.
Reduction of omega-nitrostyrenes (I) is a simple route to the important ß-phenethylamines (II). Lithium aluminum hydride has been used successfully for this transformation1-3. While this reagent is admirably suited for small-scale reactions, it is impractical for bulk preparative work because of the hazards inherent in the use of large quantities of this relatively expensive metal hydride and the difficult work-up procedures. In view of these objections, the hydrogenation of I would appear to be a more desirable procedure. This has already been done indirectly, via the oxime, in poor over-all yield4,5 and directly in highly acidic solution6,7. While good yields are reported under the latter conditions, the work-up is tedious.
We now wish to report a simple, efficient, and inexpensive method of converting I to II. This procedure, which involves the palladium catalyzed hydrogenation of I suspended in dilute hydrochloric acid8, is general and gives good yields of II as the hydrochloride salt. A typical procedure is given in the Experimental Section and several examples are listed in Table I.
To a suspension of X g of an omega-nitrostyrene in X mL of conc. hydrochloric acid is added ca. 0.2-0.3 X grams of 10% Pd-C catalyst and enough water to make the omega-nitrostyrene comprise 5-7% of the mixture. Reduction is carried out at 50-80°C under 500-1500 psi of hydrogen in an agitated autoclave. Removal of the catalyst, evaporation of the filtrate, and trituration of the residue with acetone normally affords the hydrochloride salt of the ß-phenethylamine pure enough for further use. In rare cases, when the hydrogenation filtrate is not colorless because of impurities in the omega-nitrostyrene, the aqueous filtrate is extracted with an immiscible organic solvent prior to evaporation.
A rocking autoclave was charged with 207g (1.07 mol) of 3,4-methylenedioxy-ß-nitrostyrene9, 207 mL of conc. hydrochloric acid, 65g of 10% Pd/C and the total volume was adjusted to 3500 mL by the addition of water. The mixture was hydrogenated at 55°C and an initial pressure of 800 psi until there was no further uptake, about 4 h. After cooling, the catalyst was removed and the colorless filtrate was evaporated to dryness under reduced pressure. Benzene was added to the residue and the evaporation was repeated to remove traces of water. The white, solid, residual ß-(3,4-methylenedioxyphenyl)ethylamine hydrochloride, after trituration with three 250 mL portions of acetone and drying at 70°C in a vacuum oven, weighed 153g (71%); mp 212-214°C10.
The ß-phenethylamine hydrochlorides listed in Table I were prepared by this procedure from the corresponding omega-nitrostyrenes.
Table I: ß-Phenethylamine Hydrochlorides (II*HCl)
a - Recrystallized; b - as free base; c - not recrystallized
 Dornow and G. Petsch, Arch. Pharm., 248, 160 (1951)
 F. Benington and R. Morin, J. Amer. Chem. Soc., 73, 1359 (1951)
 F. A. Ramirez and A. Burger, J. Amer. Chem. Soc., 72, 2781 (1950) (../rhodium/chemistry /lah.ph
 E. Späth, Monatsh. Chem., 40, 144 (1919)
 F. Zymalkowski, "Katalytische Hydrierungen", Ferdinand Enke, Stuttgart, 1965.
 M. Green, Patent US3062884 (1962)
 P. N. Rylander, "Catalytic Hydrogenation over Platinum Metals", Academic Press, New York, N. Y., 1967.
 The first example of this procedure was the preparation of 4-Hydroxy-3-Methoxyphenethylamine reported by A. Brossi, J. Van Burik, and S. Teitel, Helv. Chim. Acta., 51, 1978 (1968) prior to the development of the general procedure herein reported.
 E. Knoevenagel and L. Walter, Ber., 37, 4502 (1904) (../rhodium/pdf /knoevenagel.
 P. Medinger, Monatsh. Chem., 27, 244 (1906)
 J. Buck, J. Amer. Chem. Soc., 55, 3388 (1933)
 J. Buck, J. Amer. Chem. Soc., 54, 3661 (1932)
 M. Jansen, Chem. Abstr., 25, 5405 (1931)
Kindler: Phenylacetonitriles to Phenethylamines
(Rated as: good read)
This is reference #5 from Post 471993 (Rhodium: "Catalytic Reduction of Mandelonitriles", Serious Chemistry):
Studien über den Mechanismus chemischer Reaktionen. II.
Ûber den Mechanismus der Synthese von sekundären und tertiären Aminen durch Reduktion
Ann. Chem. 485, 113-126 (1931) (../rhodium/pdf /nitrile.kind
____ ___ __ _
This is reference #4 from Post 448639 (Chimimanie: "Phenethylamines via Mandelonitrile Carbamates", Serious Chemistry):
Studien über den Mechanismus chemischer Reaktionen. XI.
Ûber die Lenkung der Katalytischen Hydrierung bei Estern des Mandelonitrils
Karl Kindler und Karl Schrader
Ann. Chem. 564, 49-54 (1949) (../rhodium/pdf /mandelonitri
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