Methyl methacrylate hydroformylation

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. 

Hydroformylation of norbomene proceeds slowly in spite of the expected reactivity of the strained double bond. Racemization of the product aldehyde does not occur under the reaction conditions. The hydroformylation of methyl methacrylate gives only one isomer, which is a useful chiral synthon. Dimethyl itaconate also can be hydroformylated using (12) as the chiral ligand to give aldehyde product in 82% ee accompanied by hydrogenated ester.64... 

As reported above, a literature survey shows that the hydroformylation of this class of alkene has been scarcely investigated. Indeed, these studies have been devoted exclusively to the hydroformylation of arylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethoxyethyl acrylate, and 2-ethylhexyl acrylate (Eq. 4) [18-21], Most attention has been focused on the hydroformylation of methyl acrylate to 2-formylpropanoate ester since the latter is used extensively for the synthesis of pharmaceuticals and may also be considered as a potential source of methyl methacrylate [18]. 

A method of synthesis is given in a Japanese patent (Saito and Tokito, 1995), by hydroformylation of methyl methacrylate, followed by oxidation and hydrolysis. 

Commercial petrochemical processes using syngas or carbon monoxide are based on four principal classes of reactions phosgenation, Reppe chemistry, hydroformylations, and Koch carbonylations. Phosgenation is a key step in the manufacture of polyurethanes, polycarbonates, and monoisocyanates. Reppe chemistry is the basis for acetic acid and acetic anhydride production as well as formic acid and methyl methacrylate synthesis. Hydroformylations utilize syngas in the oxo synthesis to make a wide variety of aldehydes and long-chain alcohols. The fourth class of reactions are Koch carbonylations. Koch carbonylations are used commercially to produce neo acids which are specialty products that serve markets similar to 0X0 alcohols. 

Enantioselective hydroformylation of 2,3-dihydrofuran could be catalyzed by a series of chiral Rh(II) catalysts (13JOC4231, 130L3634). The linear cross-dimerization between methyl methacrylate and 2,5-dihydrofuran could be catalyzed by Ru(0)-naphthalene complexes containing a bicyclononadiene ligand (130L2486). 

Scheme 5.38 Preparation of methyl methacrylate via a hydroformylation-hydrogenation sequence using different catalysts.

Table 19. Hydroformylation of methyl methacrylate with various catalysts...

Hetorogenized Catalysts.—Reaction of [Ru(NH3)60H] + with a Faujasite-type zeolite gives a supported Ru complex, which effects hydroformylation of ethylene the catalytic species may be ruthenium clusters that are trapped in the zeolite cages. The effect of reaction conditions upon the selectivity of the hydroformylation of methyl methacrylate with [RhH(CO)(PPh3)3] or its polymer-anchored analogue has been investigated and hydroformylation of hex-l-ene and cyclo-octa-1,5-diene has been carried out with cobalt, rhodium, and platinum-tin complexes anchored to an ion-exchange resin via quaternary amino-phosphines. ... 

Hydroformylation of acrylate esters is a potentially very important reaction since the branched aldehyde product gives an entry point to production of important pharmaceuticals and methacrylate ester monomers. Hydroformylation of methyl acrylate (Scheme 20) proceeded in toluene with [Rh(acac)(CO)2] + PlCeHsla at 50°C and 5 MPa CO/H2 with a TOF of 225 h , aldehyde yield 95.4% and a branched to normal aldehyde ratio of more than 200 (165). In an aqueous organic biphasic system (40 mL toluene -I-10 mL water), the initial TOF increased to 545 h, retaining the high regioselectivity (b/n = 128). This effect is not unprecedented— polar solvents may facilitate reactions with polar intermediates or products which are strongly solvated. However, when the reaction was catalyzed with the same Rh-catalyst in a supported aqueous phase on silica gel. 

Though SAP systems usually exhibit a better activity than biphasic systems, both are in most cases inferior to simple homogeneous reactions. The hydroformylation of methyl acrylate is an example of the entirely different behavior. Hydroformylation of acrylic acid derivatives can be of considerable industrial importance [140], as it gives mainly formylpropionic acids, which are viable precursors of methacrylate monomers and can be used for preparation of several important pharmaceuticals ... 

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