GIBSON MICHAEL STEVEN (US)
GUAN HAIRONG (US)
CHAKRABORTY SUMIT (US)
DAI HUIGUANG (US)
BHATTACHARYA PAPRI (US)
UNIV CINCINNATI (US)
| WO2004096735A2 | 2004-11-11 |
| US20110237814A1 | 2011-09-29 |
| CLAIMS What is claimed is: 1. A homogeneous method of hydrogenating a carbonyi compound to produce a hydrogenated reaction product, comprising contacting said carbonyi compound with molecular hydrogen in the presence of an iron hydrido-borohydride catalyst complex having amino- phosphate pincer ligands and represented by the formula: wherein each R is independently selected from aromatic moieties and all y! moieties X is selected frora hydrogen and boroiiydride; and A, B, C, and D are each independently selected from hydrogen, aromatic moieties, and a!kyl moieties. 2. The method of claim 1, wherein said carbonyi compound is an ester. 3. The method of claim 2, wherein said ester is selected from tire group consisting of aromatic, aliphatic, methyl, isopropyl, butyl, long-chained, branched, non-branched, primary,, secondary, wax ester, and glyceride. 4. The method of claim. 2, wherein said carbonyi compound is a fatty acid ester, preferably said fatty acid ester has from 3 to 40 carbon atoms. 5. The method of claim 4, wherein said hydrogenated reaction product is a fatty alcohol. 6. The method according to any of the preceding claims, wherein contacting the carbonyi compound with molecular hydrogen is performed at a temperature of from 20°C to 200 °C and a pressure of from.50 to .2000 psig. 7. The method according to any of the preceding claims, wherein said catalyst complex is present at a level of from.0.02 to 5 mole ¾. 8. The method according to any of the preceding claims, wherein the yield of hydrogenated reaction product is from 5% to 100%. 9. The method according to any of the preceding claims, not comprising the addition of exogenous sol vent. 10. The method of claim 9, wherein said exogenous solvent is a reaction dilution solvent, preferably said reaction dilution solvent is selected from the group consisting of toluene, tetrahydrofuran (IMF), dioxane, methanol, ethanol, and combinations thereof. 1 1. A method of reducing an ester moiety to an alcohol moiet comprising contacting the ester moiety with a catalyst represented by the formula: wherein each ft is independently selected from aromatic moieties and alky! moieties; X is selected from hydrogen and borohydride; and A, B, C, and D are each independently selected from hydrogen, aromatic moieties, and alky! moieties, preferably where A and B collectively are members of a first cyclic moiety, said first cyclic moiety being aromatic or alkyl and having five or six members; and where C and D collectively are members of a second cyclic moiety, said second cyclic moiety being aromatic or alkyl and having five or six members, more preferably where each of A, B, C, and D are hydrogen. 12. The method of claim 1.1, where the catalyst has the following formula: 13 , A method of reducing an ester moiety to art alcohol moiet comprising contacting the ester moiety with a catalyst complex represented by the formula: wherein each R is independently selected from aromatic moieties and alkyl moieties; is selecied from borohydride, chloride, bromide, and iodide; A, B, C, and D are each independently selected from hydrogen, aromatic moieties, and alkyl moieties, preferably where A and B collectively are members of a first cyclic moiety, said first cyclic moiety being aromatic or alkyl and having five or six members; and where C and D collectively are members of a second cyclic moiety, said second cyclic moiety being aromatic or alkyl and having five or six members, more preferably where each of A, B, C, and D are hydrogen; and MOR' represents sodrum methoxide, sodium eihoxide, or potassium tertiary butoxide. 14. The method of claim 13, wherein the catalyst complex is represented by the formula: e) |
HOMOGENEOUS HYDROGENATION OF ESTERS EMPLOYING A COMPLEX OF IRON AS C ATALYST
FIELD OF THE INVENTION
The present in vention relates to a homogenous process for the hydrogenation of organic carbonyl compounds.
BACKGROUND OF THE INVENTION
Hydrogenation of esters is an industrially important process and is used to manufacture alcohols on a multi-million ton scale per annum for numerous applications. Long-chain or fatty alcohols, in particular; are widely used as precursors to surfactants, plasiieizers, and solvents. In 2012, world consumption of fatty alcohols grew to 2.2 million metric tons, and the global demand was projected to increase at a. compound annual growth rate of 3-4% from 2012 to 2020. Currently, about 50% of fatty alcohols are considered "natural fatty alcohols" as they are produced through hydrogenation of fatty acid methyl esters thai are derived from coconut and palm kernel oils, among other renewable materials.
Current technologies for the large scale ester hydrogenation to fatty alcohols (e.g. detergent length methyl esters, primarily <¾ - <¾) typically utilize a heterogeneous catalysts such as copper-cliromite and operate under extreme temperatures (250 ~ 300 °C) and pressures (2000-3000 psig of ¾ pressure). While effective, these processes are very energy and capital intensive. Alternatively, homogeneous catalysts containing precious metals such as ruthenium and osmium have been reported but often require large amounts of additives, such as an organic or inorganic bases and added solvents to obtain commercially acceptable yields.
Accordingly, it would, be desirable to provide an. alternative method to transform esters to alcohols under less harsh conditions (e.g., temperature, pressure), thereby leading to reduced energy and capital expenditures. It would also be desirable if the hydrogenation process is more environmentally friendly, generating no or only minimal waste, and not requiring the use of precious metals. Further,, it would be advantageous to provide a method whereby refined oils can be directly converted to alcohols through hydrogenation without the need to first convert the oils to fatty acid methyl esters.
SUMMA Y OF THE INVENTION '
The present invention provides a homogeneous method for the hydrogenation of esters under relatively mild conditions by employing molecular catalysis based on iron, which is an earth abundant and environmentally benign metal. The method is well-suited tor catalyzing the hydfogeiiatiOR of a wide variety of organic carbonyls without generating non-alcohol byproducis. The homogeneous method comprises contacting organic carbonyls with .moieciilar hydrogen {¾) in the presence of the iron-based catalyst. Further, the method is effective for the conversion of refined oils, such as coconut or palm, directly to detergent-length alcohols withou the addition of solvent ("neat") thus eliminating or minimizing the generation of harmful wastes.
BRIEF DESCRIPTION OF THE DRA WINGS FIG, 1 is a proposed catalytic cycle for the hydrogenation of esters to alcohols using the compound of Formul 2
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method of hydrogenating a carbonyl compound to produce a hydrogenated reaction product. The method comprises contacting the carbonyl compound with molecular hydrogen in. the presence of an. iron hydrido-borohydride catalyst complex having ammo-phosphine pincer ligands and represented by the formula:
(Formula 1 )
wherein each R is independentl selected from aromatic moieties and alky I moieties; X is selected from hydrogen and borohydride; and A, B, C, and D are each, independentl selected from hydrogen, aromatic moieties, and aikyl moieties. The method herein provides efficient, inexpensive hydrogenation of esters (e.g., aromatic, aliphatic, fatty acid esters) under mild conditions.
For example, one iteration of the iron hydrklo-borohydrsde catalyst complex of the present invention can be represented by the formula:
(Formula 2} Any suitable carbonyl compounds, such as esters, araid.es, aldehydes, and ketones, can. be hydrogenated using the present method. For example, such esters can include aromatic, aliphatic, methyl, isopropyl, butyl, long-chained, branched, non-branched, primary, secondary, wax ester, and glyceride. in certain aspects, the carbonyl compound can be a fatty acid ester. The fatty acid ester chain, can typically have from 3 t 40, or from 10 to 20, carbon atoms.
Typically, the step of contacting the carbonyl. compound with molecular hydrogen, is performed at a temperature of from 20°C to 200 and a pressure of from 50 to 2000 psig, or from 500 to 1200 psig, or from 700 to 800 psig. The carbonyl compound is part of a reaction, mixture that, comprises, consists of, or consists essentially of the carbonyl compound. The cataiyst is mcltided in an effective amount to facilitate the reaction. For example, cataiyst can be present, at a level of from 0.02 to 5 mole %, or from 0,02 to 10 mole %, or from 0.5 to 2,0 mole %. Using this method, the hydrogenated reaction, product yield range from 5% to 100%, from 25% to 99%, or from 60% to 99% in particular iterations.
In certain aspects, the method does not comprise the addition of exogenous solvent. As used herein, "exogenous solvent" means solvent added to the reaction mixture above the amount that may already be inherently present in the reaction mixture, .For example, exogenous solvent would include solvent added as a reaction dilution solvent, such as toluene, tetrahydrofuran (THF), dioxane, methanol, e hanol and combinations thereof.
In another aspect, the invention provides a method of reducing an. ester moiety to an alcohol moiety. The method comprises contacting the ester moiety with a catalyst represented by Formula f , as above.
In some iterations, A and B collectively are members of a first cyclic moiety that can be either aromatic or aiky!, and that has five or six members; and where C and D collectively are members of a second, cyclic moiety that can be either aromatic or alky 1. and that has five or six members . In others, each of A, B, C, and D are a hy drogen atom,
in some iterations of the method of reducing an ester moiety to an alcohol moiety, the catalyst has the " formula represented by Formula 2, above. In yet another aspect, the method of reducing an ester moiety to an alcohol moiety comprises contacting the ester moiety with a catalyst complex represented by the formula;
(Formula 3) wherein each R is independently selected .from aromatic moieties and alky I -moieties; X is selected from bo.rohydri.de, chloride, bromide, and iodide; A, 8, C, and D are each independently selected from hydrogen, aromatic moieties, and alkyl moieties; and MOR' represents sodium methoxide or potassium, tertiary huioxide.
In some cases, A and B collectively are members of a first cyclic moiety thai is aromatic or alkyi, and that has five or six members; and where C aad D collectively are members of a second cyclic moiety that is aromatic or alkyl, and thai has five or six members, m others, each of A, B, C, and. D are hydrogen atoms.
in additional aspects, the catalyst complex for reducing ester to alcohol is represented by the formula;
(Formula 4)
Synthesis of the iro pincer hydrido borohydride complex herein can be accomplished in two steps, as shown by Equations i and II below.
(Equation )
(Formula 5) (Formula 6} la the first step, the ί! ΡΝ(Η)Ρ pincer ligand (Formula 5) is treated with anhydrous FeBrj and CO (15 psig) in THF that results in a deep blue iron pincer hydrido borohydride complex using the following procedure. Example I exemplifies this synthesis step. The desired complex (Formula 2) is prepared, from that of Formula 6 in 85% yields by a reaction with an excess of NaBFU, as shown by Equation ίί. Example S B herein exemplifies this synthesis step.
(Formula 6) (Formula 2)
An iron monohydride complex (Formula 7) can also be synthesized similarly from Formula 6 employing one equivalent of aBFU (Equation 3), Example IC herein exemplifies ibis synthesis step.
ation 1ΙΠ
(Formula e) (Formula 7)
Tins catalytic system is also effective for the conversion of coconut oil derived fatty acid methyl esters to detergent alcohols withoui adding exogenous solvent (performed "neat").
EXAMPLES
EXAMPLE 1 - Catalyst Synthesis
Example 1 A - Synthesis of iPf PN(H)P!Fe(CO)Br 2 (Formula 6), l.n a glovebox, a 100 mL oven-dried Schlenk. flask equipped with a stir bar was charged, with anhydrous FeB¾ (510 mg t 2.36 mmol) and 30 mL of THF, which resulted in an orange solution. A TFfF solution of (10 wi%, 9,0 mL, 2.60 mmol) was added and, upon mixing with the FeBr 3 solution for a few minutes, a. thick while precipitate .formed. The flask was connected to a Schlenk line, and the argon inside the flask was replaced with CO by performing a freeze-pump- tha cycle. When mixed with CO and warmed, to room temperature, the white precipitate quickly dissolved to yield a deep blue solution. The solution was stirred under 1 5 psig of CO fori h followed by evaporatio to dryness under vacuum. The resulting blue residue was washed with pentane ( I S niL χ 3) and dried under vacuum to give the titled compound as a blue powder ( 1 .20 g, 93% yield). The ¾ NM spectra of this complex showed broad resonances, presumably due to a small amount of paramagnetic impurity. This compound can be exposed to air briefly without significant decomposilion. Ή NMR (400 MHz, CD 2 C¾, S)\ 1.42 (br, P€E(C%k 24H} ? 2.09 (b.r, CH 2> 2H>. 2.51 (br, C¾, 2H) t 2.77 (br, ?CH(CB 2 , 4H), 3.46 (br, Cffi, 2.H), 3.69 (br, C¾ 2H), 5.39 (br, NH, 1.Η). Ή NMR. (400 Hz, C 6 D 6 , d): 1 ,22-1 .26 (ra, PCB(C/¾, Γ2Η), 1.30-1.48 (m, PCH(CH ? ) 2 , 12H), i .52- 1.68 (m, CH 2 , 2H), 1.80-1 .92 (m, C¾ 2H), 2.70-2.88 (m, PCH(CH 2 ) 2 ÷ C¾ 6H), 3.13-3.24 (m, CJ¾ 2H), 4.87 (t, P-H - 12 Hz, NH, 1Η). Ci ' \ NMR ( l.O i M¾ CD 2 CI 2 , S): 19.16 (s, PCH(C¾) 2 l 19.47 (s, PCH(CH. 2 ) 19.93 (s, PCH(6¾;b), 20.38 (s, PCHCOT J 23,81 [t, J C -p = 9. Hz, CHfCHj)*), 25.4 (i, J > = 1 1.1 Hz, PtH(CH 3 ) 3 ;), 26.94 (I, Jc-p ::: 6.7 Hz, NC¾ ¾), 50.80 it, J C -p ::: 4.3 Hz, (1Μ¾), 227.29 it, J C -p ::: 22.4 Hz, FeCD). 3 ¥{Ή| NMR ( 162 MHz, CD CI 2 , S): 68.4 (s). Si .P { ¾ NMR (162 MHz, C¼D< >5 S): 68.4 (s). ATR.-IR (solid): v(N-H) = 3188 cm '1 , v(CO) = 1951 and 1928 era "5 . Transmissioti-IR (in THF): v(CO) === 194 ! cm *1 . Anal. Cakd for C s 7 Hj 7 OP 2 Br 2 Fe: C, 37.59; H, 6.79; N, 2.55; Br, 29.50. Found: C, 37.36; H, 6.77; N, 2.63; Br, 29.22.
Example IB - Synthesis of ,Pf PN(H)FiFe(H)iCO)(BH 4 ) (Formula 2). Under an argon atmosphere, a 10 mL oven-dried Schlenk flask equipped with a stir bar was charged with Formula 6 (400 nig, 0.73 mraol) and NaBFU ( 138 mg, 3,65 mmol). Adding 50 mL of dry and degassed ethanol to this mixture at 0 "C at first resulted in a green solution, which changed its color to yellow within a few minutes. The resulting mixture was gradually warmed to room temperature and then stirred for additional 16 h. Removal of the volatiles under vacuum afforded a yellow solid, which was treated with 80 mL of toluene and then filtered through a pad of Celite to give a yellow solution. Evaporating the solvent under vacuum yielded the desired compound as a bright yellow powder (250 mg, 85% yield). This compound can be exposed to air briefly without significant decomposition.
j i H r pN(H)P;|Fe(DXCO)(BD ) ^p ormu | a 2- £ 5 ) w re synthesized similarly from Formula 6 and NaBD 4 . Ή NMR (400 MHz, QD <5 , S -19.52 (i, :::: 50.4 Hz, Fe/ IE), -2.73 (br, FeB¾, 4H), 0.86-0.91 (m, PCHCCfth, 6H), tOS-L U (m, PCM(C¾} , 6H), 1.1 6-1 .21 (m, CHCCHsk f>H), 1.47- 1 ,60 (m, PCH(C¾) 2 + PCff(C¾) 2 , I OH), 1 .67-1.71 (m, ¾ 2H), 1 .97- 2. 1 (m, C¾, 2H), 2.36-2.4 (m, C¾, 2H), 2,76-2.79 (m, t¾, 2H), 3.87 (br, NH, 1Η). n C V hi\ NMR (101 MHz, C 6 D 6 , S): 18.42 (s, PCH(6¾> 2 ), 19.17 (s, PCH(CH,) 2 ) > 20.58 (s, PCH(C¾) 2 ), 20.94 (s, PCH(6¾) 2 ), 25,40 (t, J c .p = 12,8 Hz, PfB(CH 3 ) 2 ), 29.08 (t, J c * = 7.5 Hz, NC¾6¾), 29,74 (t, Jc-F » 9.7 Hz, PC¾(CH 3 ) 2 ), 54, 17 (t, J c .? = 5.8 Hz, NC¾CH 2 ), 222.56 (t, J . v » 25.8 Hz, FeOQ). · ? ! Ρ | Ή] N R (1 2 MHz, C 6 ¾, #) 99.2 (s). 1 l B NMR (128 MHz, -33.9 (quiu, f ,¾ i - 77.9 Hz). U B{ ] M} NMR ( 128 MHz, CA, ·$): -33.9 (s). ATR-IR of Form ula 2 (solid): v(N-H) - 3197 era *1 , v(8-H rera , ( „ ai ) - 2357 cm "5 , v(B-H ¼Mg mg) *" 2038 cm * 1 , v(CO) - 18 6 cm \ v(FeH) = 1832 cm '1 . ATR-IR of Formula 2-ch (solid): v(N-H) » 3198 cm *1 , v(B-D liimiIi!li ) - 1772 cm "5 , v(B-D ln 1!18 } = 1493 cm " v(CO) = 1 95 cm "5 , v(FeD) = 1327 cm "1 . Anal. Calcd. for C f 7H 42 BNO.P 2 Fe: C. 50.40; H, 10.45; N, 3.46. Found: C, 50.34; H, .10.25; N, 3.36.
Example 1 C - Synthesis of [ l ' f P (H)P|Fe(H)(CO)(Br) (Formula 7). Under an argon aimosphere, a 100 mL oven-dried Schlenk flask equipped with a stir bar was charged with Formula 6 (100 mg, 0.182 ramoi) and aBH.$ (7.0 rag, 0, 185 mmol). Adding 15 mL of dry and degassed ethauol to this mixture at 0 °C at first resulted in a gree solution, which changed its color to orange within a few minutes. The resulting mixture was gradually warmed to room temperature aid then stirred for additional 16 It. Removal of the voiatiles under vacuum afforded an orange solid, which was treated with 40 mL of toluene and then filtered through a pad of Celiie to give an. orange solution. After the solution, was concentrated to ~3 mL under vacuum, it was carefully layered with - 10 mL of pentane and placed in a refrigerator (0 °C). Orange crystals of the desired compound formed within a day. Decantation of the top layer using a cannula followed by solvent evaporation afforded the titled compound (60 rag, 70% yield). This compound is air sensitive and should be handled under an inert atmosphere. Ή NMR (400 MHz, C Ds, <>}: -22.77 (L ,/p-K - 52.0 Hz, FcH, I H), 0.86 (hr, PCH(CJ¾)a, 6H), I .12 (br, PCH(CH 3 ) 2 , 6H), 1 ,22 (br, PCH(C¾} 2 , 6H), 1.58-1.69 (m, Q¾ + PCH(C¾) 2 ÷ PCH(C¾) 2> 12Η), 2.03 (br, CH2, 2Η), 2.64 (br, CH 2 , 2Η), 3.07 (br, C¾, 2Η), 3.55 (br, NH, 1Η). Ή NMR. (400 MHz, THF- , S) -22.63 (t, . u - 52.0 Hz, FeH IH), 1.07-1.12 (ra, PC.H(CH 3 s 1J -1.25 (m, FCH(C/¾) 2 , 6H), 1.29-1.33 (m, PCH(C¾k 6H), 1 .48-1.54 (m, PCH.(CH 3 ) 2 , 6H), 1.70-1.82 (m, PCH(C¾) 2 , 2Η), 2.08-2.18 (m, PCH(CH ¾ 211), 2.22-2.34 (m, C¾ 2H), 2.35-2.44 (m, C¾ 2H), 2.81-2.95 (m, C¾, 2H), 3.18-3.34 (m, C¾ 2H), 3.59-3.72 (m, NH, IH). 1 ¾ { i H} NMR (101 MHz, C (> D 6 , S): 18.08 (s, PCH(6¾} 2 ), 19.19 is, PCH(0¾) 2 ), 20.70 (s, PCH((¾) 2 ), 20.86 (s, PCH(6¾)j), 24.70 (t, J c ,? - 12.1 Hz, PCH(CHi) 2 ), 28.45 (t, J c * - 10.1 Hz, CHiCBjh), 29.63 (i, ,/c.j> - 8, 1 Hz, NCH 2 <¾.h 53.72 (t, c = 6,1 Hz, NC¾C¾), 224.1 (t, Λ-ρ - 26,3 Hz, FeOO). ?\ l R} NMR (162 MHz, C {i D 6 , <$}: 93.5 (d, p-a - 9.7 Hz, residual coupling due to incomplete decoupling of the high-Held hydride resonance). ATR-IR. (solid): v( -H) ~ 3173 cm " v(CO) - 1894 cm *1 , v(FeH) ==== 1852 cm *! . Altai. Calcd for CnHnNOPjBrFe: C, 43.43; H, 8, 15; N, 2.98; Br, 16.99. Found: C, 43.47; H, 8.20; N, 2.93; Br, 1 .77. S
EXAMPLE 2 ···· Optimization of the Catalytic Conditions.
In a g!ovebox, an iron complex (Formula 2, 6, or 7; 25 pmoi), additive (if needed), methyl benzoate ( 1 5 pL, 833 proo ' l), and tridecane (80 itL, 328 pmol, internal standard) were mixed with 0.5 raL of solvent in a small test tube, which was placed in a HEL CAT 18 high- pressure vessel. The vessel was sealed, flushed with H 2 . three times, and placed under an appropriate ¾ pressure. The vessel was then heated by as oil bath at appropriate temperature. A small aliquot was withdrawn from the test tube and diluted with approximately 4 mL of ethyl acetate prior to GC analysis. The percentage conversion for each reaction was calculated by comparing the integration of methyl benzoate with that of the internal standard. The results are summarised in Table I below.
Table 1, Catalytic activity of iron complexes for the hydrogenation of methyl ' benzoate.
PhCIbOB
Catalyst Pressure Temp. Time Solvent Conversion Yield
Formula 6
(3 mol%) NaBH4 (15 mol%) 150 psig "C 3 h TBF 0 % 0 %
Formula 6
(3 moi%)/KO ! Bu (10 mol%) 150 psig ! ! 5 "C 3 h TBF 0 % 0 %
Formula 7
(3 mol%) 150 psi« Π 5 '€ 3 TBF 0 % 0 %
Formula 7
(3 mol%yKO { Ba. ( 1 mol%) 1 0 psig 1 ! 5 - ' C 3 h THF > 5 % 72 %
Formula 2 (3 mof¾) 150 psig 1. 15 %: 3 h THF 100 % 94 %
1 ,4-
Formula 2 (3 mot%) 150 psig US X " dioxaue 100 % 92 %
Formula 2 {3 mo!%) 150 psig 1 1 X 3 h toluene 100 % 99 %
Formul 2 (2 mot%) i 50 psig 1 15 "C 3 toluene 100 % 82 %
Formula 2 (3 mof¾) 1 0 psig ns x: 3 h toluene 82 % 44 %
Formula 2 (3 rnol%) 60 psig ! ! 5 X. 3 toluene 0 % 0 %
Formula 2 (3 mol%) i 50 psig 85 °C 3 h toluene 100 % 95 %
Formula 2 (3 mof¾) 150 psig 60 ··(: 3 h toluene 0 % 0 % Formula 2 can be directly employed as a catalyst (no base is needed) for ester ydrogenation. A general scheme for this hydrogeaation reaction is shown, by Equation. IV:
(I u 3 mol% [fonmtia 2] ^
R OR' toluene or THF i-n: ρ(Η¾ - 230 sig (Equation IV) a n 115 -0
- R'OH
Table 2 illustrates the scope of esters tha can be hydrogeriated using the complex of Formula 2 as the catalyst under the aforementioned conditions.
T able 2, Scope of esters
Unsubstituted aromatic esters such as methyl benzoate, ethyl benxoate, and benzyl benzoate were hydrogenated to the benzyl alcohol with high isolated yields (90-95%). Aromatic methyl esters containing -CF3, -O e, and -CI substituents at the para position reacted smoothly under these conditions to afford the corresponding alcohols io good yields. Esters containing electron- wimdrawmg groups (-CF¾, -CI) reacted, faster than the one with electron-donating substituent (-OMe). More challenging aromatic and aliphatic diester substrates were also hydrogenated successfully, albeit with slower catalytic turnovers.
It is believed that under the catalytic conditions, BH? dissociates from the complex of Formula 2 to release the active #¾2/¾$-dihydride species. The acidic H and the hydridie FeH hydrogens can now be transferred simultaneously to the ester substrate to yield a hemiacetal intermediate and a 5~coordinate iron, species, which is converted back to the /rww-dihydride via the uptake of j¾. The hemiacetal intermediate can dissociate into an. alcohol and an aldehyde, which is further reduced by the /mav-dihydride. The proposed catalytic cycle for the hydrogenation of esters to alcohols using the compound of Formula 2 is shown in FIG. .1. EXAMPLE 3 -- Neat hydrogenatioa of fatty acid methyl esters
Example 3A ···· Small Scale (22 mL Parr reactor). Methyl ester (Procter & Gamble Chemicals CE-1270) and catalyst (~i mole %) were added to a 22 mL Parr reactor along with a magnetic stir bar. The reactor was closed, flushed with FT, pressurized and placed in a preheated aluminum heating block ( 135 X). After the determined period of time, the reactor was cooled, the pressure veined, opened and a sample removed for analysis by GC to determine the yield of alcohol formation. Selected results are in Table 3 below.
These are believed to be the first successful hydrogenation of esters carried out under neat conditions using a homogeneous Fe- based catalyst
Table 3
Example 3.B - Larger Scale (300 mL Parr reactor). To a 300 mL high pressure stainless steel Parr reactor were added iron catalyst (Formula 2, 0.72 g, 0.26 mol%), and CE-1270 (149.96 g, 676.2 mmol). The reactor was sealed, flushed with F (4x) followed by pressuring to 750 psig. Stirring was started (-1000 rpni) and the reactor set to warm to 135 °C. Time - 0 was started when the reaction had reached 1 35 °C. The reaction was continued under these conditions for 3 hours with samples removed for GC analysis at time ::: 0 minutes. 20 minutes, 40 minutes, I hour, 2 hours and 3 hours. For each sample, the conversion, selectivity and alcohol yield were determined with results shown in the Table 4,
Table 4
Time % Conversion % Selectivity % Yield
0 minutes 2.3 100.0 ■ 7
20 minutes 24.5 95.7 23.4
40 minutes 26.2 937 24,6
1 hour 26.7 93.0 24,8
2 hours 27.5 90.9 24.
3 hours 28.1 88.8 25.0 Example 3C -·· Lower Temperature (300 niL Pan' reactor). To a 300 mL high pressure stainless steel. Parr reactor were added iron catalyst (Formula 2, 0.74 g, 0.27 mol%), and CE-
1270 (149.96 g, 676.2 mmol). The reactor was sealed, flushed with ¾ (4x) followed by pressuring to 75 psig. Stirring was started { -1000 rpm) and the reactor set to warm to 115 °C. Time ::: 0 was started when the reaction had reached 1 15 °€. The reaction was continued under these conditions for 3 hours wit samples removed for GC analysis at time - 0 minutes, 20 minutes, 40 minutes, I hour, 2 hours and 3 hours. For eac sample, the conversion, selectivity and alcohol yield were determined with results shown in Table 5.
Table 5
EXAMPLE 4 -Neat hydrogenatioii of oil directly to fatty alcohols
Refilled, bleached and deodorized Coconut oil (Procter & Gamble Chemicals) and catalyst (-2 weight %) were added to a 22 niL Parr reactor along with a magnetic stir bar. The reactor was closed, flushed with ¾, pressurized and placed in a pre-heated aluminum heating block ( 135 °C) After stirring for 23 hours, the reactor was cooled, the pressure vented, opened and a sample removed for analysis by GC to determine the yield of alcohol formation, 1 i ,67% fatty alcohol (Cg -· Cie) was obtained. The Cu alcohol was not tabulated as it was not able to be clearly discerned from other peaks in that range on the GC chromalogratn.
The dimensions and values disclosed herein are not to be understood as being strictly iimded to the exact numerical values recited, instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 miii. "
Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference i its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or thai it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shail govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can he made without departing from the spirit and scope of the invention, it is therefore intended to cover in the appended claims all such changes and modifications that are within, the scope of this invention.
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