Acetone cyanohydrin catalyst

Single-pass conversions of acetone cyanohydrin are 90—95% depending on the residence times and temperatures in the generator and hold tank. Overall yields of product from acetone and hydrogen cyanide can be >97%. There are no significant by-products of the reaction other than the sodium salts produced by neutralization of the catalyst. 

Neopentyl alcohol, 40, 76 Nickel catalyst for hydrogenation of resorcinol, 41, 56, 57 Nitramines from amines and acetone cyanohydrin nitrate, 43, 84 Nitration, of amines to nitramines by acetone cyanohydrin nitrate, 43, 83... 

The ACH process has recently been improved, as stated by Mitsubishi Gas. Acetone-cyanohydrin is first hydrolized to 2-hydroxyisobutylamide with an Mn02 catalyst the amide is then reacted with methylformiate to produce the methyl ester of 2-hydroxyisobutyric acid, with coproduction of formamide (this reaction is catalyzed by Na methoxide). The ester is finally dehydrated with an Na-Y zeolite to methylmethacrylate. Formamide is converted to cyanhydric acid, which is used to produce acetone-cyanohydrin by reaction with acetone. The process is very elegant, since it avoids the coproduction of ammonium bisulphate, and there is no net income of HCN. Problems may derive from the many synthetic steps involved, and from the high energy consumption. 

Catalyst of the Cyanation Reaction. The reaction was studied in the presence of Ni(0) complexes or aryl(chloro)nickel complexes. For a clearer interpretation the corresponding results are considered separately. A variant of the process consisting in the use of acetone cyanohydrin as source of cyanide ions is also reported. 

These results suggest that the concentration of cyanide ions must be very low, even less than the solubility of NaCN in anhydrous ethanol (0.1%). In fact by saturating ethanol with NaCN at 50°C and then adding the catalyst, the reaction occurred to a limited extent. Analogous conclusions can be drawn from the results of reactions carried out with acetone cyanohydrin (Table IV). 

Research is currently directed toward development of novel technologies that may present economic advantages with respect to the conventional acetone cyanohydrin lACHl route. Mitsubishi Gas Chemical Co. has developed and patented n modified acetone cyanohydrin-based route that docs not use sulfuric acid and therefore presents the opportunity lor reduced waste costs. A nuvel C-3 route based on the palladium-catalyzed carbonylaiion of methylatelylenc has been developed by Shell Oil Co. There have been significant improvements in catalysts and resulting yields for key transformations in many routes since the 19K(K... 

Inhibitors are introduced al specific points in the process to prevent polymerization Sulfuric acid serves as catalyst in a combined hydrolysis-esterilieaiion of methacrylamide sulfate to a mixture of methyl methacrylate and methacrylic acid. Conversion of methacrylamide sulfate to methyl methacrylate can be carried out using a variety of procedures for die recovery of crude methyl methacrylate and fur separation of methanol and methacrylic acid for recycling. A schematic of the overall process is given in Figure I. The overall yield based on acetone cyanohydrin is approximately 90D Most of Ihe world supply of MMA is still produced by this process. 

The search for other amino acid-based catalysts for asymmetric hydrocyanation identified the imidazolidinedione (hydantoin) 3 [49] and the e-caprolactam 4 [21]. Ten different substituents on the imide nitrogen atom of 3 were examined in the preparation, from 3-phenoxybenzaldehyde, of (S)-2-hydroxy-2-(3-phenoxy-phenyl)acetonitrile, an important building block for optically active pyrethroid insecticides. The N-benzyl imide 3 finally proved best, affording the desired cyanohydrin almost quantitatively, albeit with only 37% enantiomeric excess [49]. Interestingly, the catalyst 3 is active only when dissolved homogeneously in the reaction medium (as opposed to the heterogeneous catalyst 1) [49]. With the lysine derivative 4 the cyanohydrin of cyclohexane carbaldehyde was obtained with an enantiomeric excess of 65% by use of acetone cyanohydrin as the cyanide source [21]. 

Acetone cyanohydrin has been prepared from acetone and anhydrous hydrogen cyanide in the presence of a basic catalyst such as potassium carbonate, potassium hydroxide, or potassium cyanide 1 by the reaction of potassium cyanide on the sodium bisulfite addition product of acetone 2 and by the action of hydrogen cyanide, prepared directly in the reaction mixture, on an aqueous solution of acetone.3... 

The problem of the hydrocyanation of conjugated carbonyl compounds has been reviewed in detail by Nagata and Yoshioka [281. The reactions proceed smootltly and base or acid catalysts are sometime useful with HCN. Cyanides (KCN. NaCN. etc.) arc recommended reagents in some cases, particularly in nonaqueous Solvents (28], and even cyanohydrins (e.g., acetone cyanohydrin) have been used as cyanation reagents. 

Nitration of chlorobenzene with n-butyl nitrate and a Nafion-H catalyst gave only a 15% yield of the chloronitrobenzenes but with acetone cyanohydrin nitrate a 49% yield was obtained with the para isomer produced with 70% selectivity.65 Using an iron exchanged montmorillonite to promote the nitration of chlorobenzene with nitric acid and acetic anhydride gave a 90% yield of the nitro chlorobenzenes in 15 minutes at 80°C. The para isomer was produced in 92% selectivity (Eqn. 22.28).68... 

Olah [40c] has drawn attention to the fact that the first solid acid catalyst was suggested by Kameo, Nishimura and Manabe (71 ]. They used polystyrene-sulphonic acid with nitric acid, but the system was unstable, as the catalyst was degraded by the strong acid. Olah and associates [72] developed a nitrating agent from n-butyl nitrate and acetone cyanohydrine nitrate by adding a per-... 

Alkynes are readily hydrocyanated in the presence of a homogeneous catalyst, especially a nickel-based catalyst system. However, zerovalent palladium compounds are reported to catalyze the reaction as well, but are less efficient [60], The reaction gives an easy access to the synthetically valuable a,P-un-saturated nitriles. The use of acetone cyanohydrin as a synthetic equivalent for the difficult-to-handle HCN provides an efficient alternative, but the substrate/ catalyst ratio has to be increased in comparison with the reaction with HCN. The regioselectivity of the reaction is controlled by steric, electronic, and chelative effects. Investigations were predominantly performed by changing the substituent pattern on the acetylenic substrate [61]. 

When certain cyclodipeptides are used as catalysts for the enantioselective formation of cyanohydrins, an autocatalytic improvement of selectivity is observed in the presence of chiral hydrocyanation products [80]. A commercial process for the manufacture of a pyrethroid insecticide involving asymmetric addition of HCN to an aromatic aldehyde in the presence of a cyclic dipeptide has been described [80]. Besides HCN itself, acetone cyanohydrin is also used (usually in the literature referred to as the Nazarov method), which can be activated cata-lytically by certain lanthanide complexes [81]. Acetylcyanation of aldehydes is described with samarium-based catalysts in the presence of isopropenyl acetate cyclohexanone oxime acetate is hydrocyanated with acetone cyanohydrin as the HCN source in the presence of these catalytic systems [82]. 

To avoid handling of hydrogen cyanide directly, cyanohydrins have been employed as a source of HCN under reaction conditions. See, for example, a disclosure of this technique employing acetone cyanohydrin and either nickel, palladium, copper or cobalt catalysts W. C. Drinkard, Jr., U.S. Pat. 3,655,723 (1972) Chem. Abstr., 77, 4986p (1972). 

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