Methyl hydroformylation

An early attempt to hydroformylate butenediol using a cobalt carbonyl catalyst gave tetrahydro-2-furanmethanol (95), presumably by aHybc rearrangement to 3-butene-l,2-diol before hydroformylation. Later, hydroformylation of butenediol diacetate with a rhodium complex as catalyst gave the acetate of 3-formyl-3-buten-l-ol (96). Hydrogenation in such a system gave 2-methyl-1,4-butanediol (97). 

Isobutyraldehyde is commonly available as a by-product of propylene/Oxo hydroformylation. Methyl isoamyl ketone is used as a solvent for ceUulose esters, acryHcs, and vinyl polymers. It is available in the United States from Eastman (Kingsport, Tennessee) (47) and Union Carbide (South Charleston, West Virginia) and was priced at 1.42/kg in October 1994. 

MMA and MAA can be produced from ethylene [74-85-1/ as a feedstock via propanol, propionic acid, or methyl propionate as intermediates. Propanal may be prepared by hydroformylation of ethylene over cobalt or rhodium catalysts. The propanal then reacts in the Hquid phase with formaldehyde in the... 

Linear terminal olefins are the most reactive in conventional cobalt hydroformylation. Linear internal olefins react at less than one-third that rate. A single methyl branch at the olefinic carbon of a terminal olefin reduces its reaction rate by a factor of 10 (2). For rhodium hydroformylation, linear a-olefins are again the most reactive. For example, 1-butene is about 20—40 times as reactive as the 2-butenes (3) and about 100 times as reactive as isobutylene. 

Butylene isomers also can be expected to show significant differences in reaction rates for metaHation reactions such as hydroboration and hydroformylation (addition of HCo(CO). For example, the rate of addition of di(j -isoamyl)borane to cis-2-huX.en.e is about six times that for addition to trans-2-huX.en.e (15). For hydroformylation of typical 1-olefins, 2-olefins, and 2-methyl-l-olefins, specific rate constants are in the ratio 100 31 1, respectively. 

Obviously, the use of a nonvolatile ionic liquid simplifies the distillative workup of volatile products, especially in comparison with the use of low-boiling solvents, where it may save the distillation of the solvent during product isolation. Moreover, common problems related to the formation of azeotropic mixtures of the volatile solvents and the product/by-products formed are avoided by use of a nonvolatile ionic liquid. In the Rh-catalyzed hydroformylation of 3-pentenoic acid methyl ester it was even found that the addition of ionic liquid was able to stabilize the homogeneous catalyst during the thermal stress of product distillation (Figure 5.2-1) [21]. This option may be especially attractive technically, due to the fact that the stabilizing effects could already be observed even with quite small amounts of added ionic liquid. 

Phosphine, amino-rhodium complexes catalysts, hydroformylation, 6,261 Phosphine, 3-aminopropyldimethyl-photographic fixer, 6,100 Phosphine, bis(2-carboxyethyl)methyl-photography... 

Styrene, a-ethyl-asymmetric hydroformylation catalysts, platinum complexes, 6, 266 asymmetric hydrogenation catalysts, rhodium complexes, 6, 250 Styrene, a-methyl-asymmetric carbonylation catalysis by palladium complexes, 6, 293 carbonylation... 

Methyl-l-hexanol has also been prepared by the reaction of 2-hexylmagncsium halides with formaldehyde,3 the reduction of 2-mctliylliexanoic acid or its ester,4 5 and by hydroformylation of 1-hexene6"8 among others. 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

A great portion of the formed 2-alkyl-branched alcohols, especially in the hydroformylation products of n-a-olefins, consists of the low-branched 2-methyl alcohols (Fig. 4). 

Llewellyn, Green, and Cowley isolated the Co-H complex [CoH(CO)3(IMes)] 26, a relatively stable complex under inert conditions [31], The authors examined the hydroformylation activity of 1-octene with Co-hydride complex 26. With 8 atm of syngas (H /CO) at 50°C for 17 h and 1 mol% 26, the conversion to aldehyde products was 47% with a l b of 0.78. However, 83% of the product was the internal aldehyde 2-methyl-octanal, indicating isomerisation competed with hydroformylation and the rate of isomerisation occurred faster than hydroformylation. 

Hydroformylation of 1-butene in the presence of the Rh catalyst gave pentanal (P) and 2-methyl bntanal as the main products. Just trace amounts of c/5-and trans-1-butene were detected as by-prodncts. No butane was detected in experiments, where a stoichiometric ratio of CO and H2 were used. Based on preliminary considerations of prodnct distribntions, a kinetic model was developed. The kinetic parameters obtained from the model were well identified and physically reasonable. The prodnct concentrations are predicted very well by the kinetic model. The kinetic model can be further refined by considering detailed reaction mechanisms and extending it to the domain of lower partial pressures of CO and H2. 

For long chain olefins, the hydroformylation generally proceeds slowly and with low selectivity in two-phase systems due to their poor solubility in water. Monflier et al. recently reported a conversion of up to 100% and a regioselectivity of up to 95% for the Rh-catalyzed hydroformylation of dec-l-ene in water, free of organic solvent, in the presence of partially methylated 6-cyclodextrins (Eq. 3.42).173... 

Other metal complexes containing Pd, Ru, Co, or Pt have also been used.176 The hydroformylation reaction can also be performed by using methyl formate instead of carbon monoxide and hydrogen.177... 

Most recently new applications for substrate-controlled branched-selective hydroformylation of alkenes substituted with inductively electron-with drawing substituents have emerged. A recent example is the hydroformylation of acrylamide with a standard rhodium/triphenylphosphine catalyst, which yields the branched aldehyde exclusively (Scheme 4) [40]. Reduction of the aldehyde function furnishes 3-hydroxy-2-methylpropionamide, which is an intermediate en route to methyl methacrylate. 

An interesting one-pot hydroformylation/Fischer indole sequence can be achieved by running the hydroformylation in the presence of a phenylhy-drazine. This protocol gave access to the methyl ester of the plant growth regulator 3-indole butanoic acid (IBA) (Scheme 16) [61-63]. A review on related tandem processes involving the hydroformylation as a key step has appeared recently [9]. 

---