1-pentene, hydroformylation

In the case of the deuterioformylation of 1-pentene in the presence of [(—)-DIOP] Pt(SnCl3) Cl as the catalyst precursor, on the other hand, the two chiral reaction products (Fig. 3) mainly arise from the two opposite enantiofaces 43). Therefore, in 1-pentene hydroformylation, the enantiomeric excess found in the chiral reaction product does not correspond in type and extent to enantioface discrimination. 

Formation of isomerized olefin in the case of cobalt catalysts occurs with a higher rate than hydroformylation only at low partial pressures (<5 MPa) of carbon monoxide in the temperature range of 80-120°C. At higher partial pressures (>5 MPa) of carbon monoxide, the rate of olefin isomerization become slower than the rate of olefin hydroformylation. Tables 5 and 6 show relevant product composition in pentene hydroformylation at two different carbon monoxide partial pressures using unmodified cobalt catalyst. 

Table 5. Effect of the Partial Pressure of Carbon Monoxide P(CO) on the Composition of Products in the Cobalt-Catalyzed 1-Pentene Hydroformylation at 100°C. ...

Pla.tinum. Platinum catalysts that utilize both phosphine and tin(Il) haUde ligands give good rates and selectivities, in contrast to platinum alone, which has extremely low or nonexistent hydroformylation activity. High specificity to the linear aldehyde from 1-pentene or 1-heptene is obtained using HPtSnClgCO(1 1P) (26), active at 100°C and 20 MPa (290 psi) producing 95% -hexanal from 1-pentene. 

It is noteworthy that a clear enhancement of selectivity for the linear hydro-formylation product is observed only with cdpp (Table 5.2-1, entry e). With all other ligands, the n/iso ratios are in the 2 to 4 range. While this is in accordance with known results in the case of PPI13 (entry a) and dppe (entry c) (in comparison to monophasic hydroformylation [69]) and also with reported results in the case of Natppts (entry b in comparison to the biphasic hydroformylation of 1-pentene in [BMIM][PF(3] [46]), it is more remarkable for the bidentate metallocene ligand dppf... 

The hydroformylation reaction strategy has recently been extended, in a novel way, to the manufacture of primary amines by hydroaminomethylation of olefins with ammonia in a two-phase system. Thus, 1-pentene was reacted with ammonia here hydroformylation to an aldehyde, with CO and H2, with subsequent reductive amination occurs in a domino reaction. The catalyst was Rh/Ir/TPPS (Zimmermann et al., 1999). 

Chart 1 Ligands used for isomerizing hydroformylation of internal octenes and 2-pentene. 

The ligands synthesized were also apphed to the isomerizing hydroformylation of more reactive 2-pentene. At 120 °C/ 20 bar quantitative conversion of olefin to aldehydes was achieved within 40 min. Trends similar to those described for internal octene hydroformylation were found. The regioselectivity obtained for the individual ligands tends to be 5% higher compared to that for the octenes. Thus, in the presence of 10 75% of n-hexanal were determined, compare Table 3. Obviously, 2-pentene is able to react more smoothly to the terminal isomer compared to olefins having the double bond in an more internal position. Illustrative for this effect are also literature results obtained for 2- and 4-octene.4,5... 

Table 4 Hydroformylation of 2-pentene with 6 Variation of T, p, solvent.0...

Stoichiometric model reactions in alkene hydroformylation by platinum-tin systems have been studied for the independent steps involved in the hydroformylation process, insertion of the alkene, insertion of CO, and hydrogenolysis, with use of Pt-Sn catalysts and 1-pentene as alkene at low pressure and temperature.92... 

In the early 1970 s, Bayer et al. reported the first use of soluble polymers as supports for the homogeneous catalysts. [52] They used non-crosslinked linear polystyrene (Mw ca. 100 000), which was chloromethylated and converted by treatment with potassium diphenylphosphide into soluble polydiphenyl(styrylmethyl)phosphines. Soluble macromolecular metal complexes were prepared by addition of various metal precursors e.g. [Rh(PPh3)Cl] and [RhH(CO)(PPh3)3]. The first complex was used in the hydrogenation reaction of 1-pentene at 22°C and 1 atm. H2. After 24 h (50% conversion in 3 h) the reaction solution was filtered through a polyamide membrane [53] and the catalysts could be retained quantitatively in the membrane filtration cell. [54] The catalyst was recycled 5 times. Using the second complex, a hydroformylation reaction of 1-pentene was carried out. After 72 h the reaction mixture was filtered through a polyamide membrane and recycled twice. 

With the RCH/RP process, it is possible to hydroformylate propene up to pentenes with satisfying space time yields. On the other hand, heavier aldehydes such as Cio (iso-decanal) or higher from the hydroformylation of nonene(s), decenes, etc. can not be separated from the oxo catalysts by conventional means such as distillation due to thermal instability at the required temperatures and thus especially needs the careful aqueous-biphasic separation technique. There are numerous attempts to overcome the problem of low reactivity of higher alkenes which is due to low miscibility of the alkenes in water [26,27b, 50a,58d]. These proposals can briefly be summarized as ... 

The first investigations of the rhodium-catalysed hydroformylation in room temperature ionic liquids were published by Chauvin et al. in 1995 [44], The hydroformylation of 1-pentene with the neutral catalysts [Rh(CO)2(acac)]/triarylphosphine was carried out in a biphasic reaction using [BMIM][PF6] as the ionic liquid (see Scheme 7.2). 

The most influential parameter in cobalt-catalyzed hydroformylation was found to be carbon monoxide partial pressure. Piacenti et al. (30) showed this to be influential for both a- and internal olefins. Results are detailed in Tables V and VI. The percent of n-aldehyde rose rapidly as the carbon monoxide partial pressure was increased up to 30-40 atm CO further increase had little effect. 1-Pentene clearly gave a higher percentage of straight-chain aldehyde than 2-pentene, but the difference was insignificant in the lower Pco experiments. 

The introduction of alkyl phosphine complexes of cobalt carbonyl as hydroformylation catalysts was reported to have a significant effect on product composition (50, 51). Slaugh and Mullineaux (52) reported that hexanol with a 91% linear distribution was formed by the hydroformylation of 1-pentene at 150°C, 500 psi, H2/CO 2.0, catalyst [Co2(CO)8 + 2(n-C4H9)3P]. Under the same conditions except at a temperature of 190°C, the n-hexanol was 84% of the hexyl alcohol produced. 

The substitution of trialkylphosphine for carbon monoxide also makes the metal-hydrogen bond more hydridic in character and results in increased reduction of the initially formed aldehyde to alcohol. Slaugh and Mullineaux (52) compared Co2(CO)g and [Co2(CO)8 + 2PBu3], each at reaction conditions of 150°C, 500 psi, H2/CO I.0, for the hydroformylation of 1-pentene. The products consisted of hexyl aldehydes and hexyl alcohols in the ratios of 95 5 and 30 70, respectively. In a negative aspect of the reaction, they observed 23% hydrogenation of alkene to alkane at a reaction temperature of 195°C with the phosphine-modified catalyst. Tucci (54) reported less alkane formation (4-5%) under more favorable reaction conditions (I60°C, H2/CO 1.2, 1 hour reaction time). 

Effect of Phosphine Type on Specificity in the Hydroformylation of 1-Pentene (52) or 1-Hexene... 

A two-stage process for the hydroformylation of butadiene to give good yields of a desired product—1,6-hexanediol—has been described (100). The first stage employed [(C6H5)3P]2Rh(CO)Br and excess triphen-ylphosphine as catalyst and reaction conditions of I20°C and 200 atm of 1/1 H2/CO in methanol as solvent. The principal product was 3-penten-l-al dimethyl acetal. This was treated with 1,3-propanediol to form a cyclic acetal, then hydroformylated with Co2(CO)8 and dodecyl-9-phospha-9-bicyclononane at 170°C and 80-110 atm of 2/1 H2/CO. The product of... 

Hydroformylation of 1-Pentene Catalyzed by (p)-(PPh2)3RhH(CO),a Compared with Homogeneous HRh(CO)(PPh3)3ll(//4)... 

One widely studied catalyst system for hydroformylation in organic solvents is Rh(CO)2(acac) combined with triphenylphosphine (or other phosphines) in varying ratios. The same catalyst has been shown to catalyse the hydroformylation of 1-pentene to n- and Ao-hexanal in [bmim][PFg] as shown in Scheme 8.10 [25],... 

Karapinka and Orchin (18) made an extensive study of the isomerization of 1-pentene under stoichiometric hydroformylation conditions. 

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