Carbon monoxide, reaction with alcoholates

With Alcohols, Ethers, and Esters. Carbon monoxide reacts with alcohols, ethers, and esters to give carboxyHc acids. The reaction yielding carboxyHc acids is general for alkyl (53) and aryl alcohols (54). It is cataly2ed by rhodium or cobalt in the presence of iodide and provides the basis for a commercial process to acetic acid. 

The essential factor which differentiates the monomeric and dimeric carbonylations seems to be the presence or absence of halide ion coordinated to the palladium. The dimerization-carbonylation proceeds satisfactorily with halide-free palladium phosphine complexes. Most conveniently, Pd(OAc)2 is used with PPh3. PdCl2(PPh3)2 can be used as a catalyst with addition of an excess of bases. The reaction is carried out at 1I0°C under 50 atm of carbon monoxide pressure in alcohol. Higher... 

Metal Hydrides. Metal hydrides generally react readily with acetylenes, often by an insertion mechanism. Cobalt hydrocarbonyl gives complicated mixtures of compounds with acetylenes. The only products which have been identified so far are dicobalt hexacarbonyl acetylene complexes (34). Greenfield reports that, under conditions of the hydroformy lation reaction, acetylenes give only small yields of saturated monoaldehydes (30), probably formed by first hydrogenating the acetylene and then reacting with the olefin. Other workers have identified a variety of products from acetylene, carbon monoxide, and an alcohol with a cobalt catalyst, probably cobalt hydrocarbonyl. The major products observed were succinate esters (74,19) and succinate half ester acetals (19). 

Carbinolamines, 87 Carbodiimides, 205-222 reaction with alcohols, 170 Carbon monoxide, as reducing agent, 336 a-Carbonyl azo compounds, 324, 326 Caro s add (permonosulfuric add), 408 oxidation with, 409 preparation of, 409 Chloramine T, 377 Chloroacetylenes 120-122 4-Chloro-l, 2-butadiene, 33 Chlorocyclohexenyl acetylene, 121 1 -Chloro-2-JV,N-diphenylaminoacetylene, 128-129... 

In this more interesting case, each monomer adds only to an end unit of the other kind (k = 0, km - 0). In the polymer, units MA and M then alternate. Coordination copolymerization of olefins and carbon monoxide, catalyzed by complex hydrides of Pd(II) or Rh(I) in the presence of an alcohol co-solvent to yield polyketo esters, provides an example [133,134] Olefin and carbon monoxide are added altematingly, and reaction with alcohol terminates the kinetic chain and restores the catalyst. For ethene as the olefin ... 

Nucleophilic substitution and addition reactions of olefins are possible with Pd2 salts. A typical example is the formation of acetaldehyde by the reaction of ethylene with water (Wacker reaction). As nucleophiles, water, alcohols, phenols, carboxylic acids, amines, enamines, carbanions derived from active methylene compounds, and carbon monoxide react with olefins with stoichiometric consumption of Pd2 salts. 

Carboxyalkylation of halides. Aryl, benzyl, and vinyl halides react with carbon monoxide and an alcohol at 100 (atmospheric pressure) in the presence of a tertiary amine and a dihalo(triphenylphosphine)palladium catalyst to form esters in good yields. In the case of vinylic halides, the reaction proceeds predominantly with retention of configuration. 

Hydroformylation is the reaction of carbon monoxide and hydrogen with olefins to produce aldehydes and derivative alcohols. It is also known as 0X0 chemistry and the alcohol products produced by this method are known as 0X0 alcohols. Of all three types of carbon monoxide reactions, Reppe reactions, Koch carbonylations, and hydroformylations, oxo chemistry currently has the greatest commercial importance. An extremely broad range of products and end use markets are served by the aldehydes, alcohols, and derivatives produced by hydroformylation. The list of products shown in Table 6 illustrates the range of oxo chemical products. 

If the alcoholysis reaction is carried out in the presence of base, the acidic cobalt hydrocarbonyl is converted into a salt. This base-catalyzed reaction has been used as the basis for a catalytic, one-step alkoxycarbonylation of alkyl halides with carbon monoxide and an alcohol (8). 

The various kinds of 2-ferrocene derivatives are synthesized by reaction with transition metal compounds in a manner similar to the orthometalation of phenyl compounds. The palladium compounds 7.54 of dimethylaminomethylferrocene react with carbon monoxide in methyl alcohol to give the 2-methoxycarbonyl compound 7.45, and subsequent treatment of the product with methyl iodide, sodium amalgam, and phosphoric acid gives l-methyl-2-carboxylic acid 7.55. Reduction of the 2-methoxycarbonyl compound 7.45, followed by treatment with NaOH, produces an alcohol 7.56, and oxidation of the compound 7.56 yields an aldehyde 7.57, as shown in Scheme 7.9. Since the starting material 7.54 is an optically active compound, as shown in Scheme 7.9, all of its derivatives are also optically active 1,2-ferrocene derivatives [68]. 

The first palladium-catalyzed carbonylations of aryl halides were published in 1974 and 1975 (Equation 17.59). ° Heck first reported the synthesis of benzoates by the reaction of an aryl iodide, carbon monoxide, and an alcohol in the presence of a tertiary amine and catalytic amoimts of the combination of palladium acetate and triphenylphosphine. Concurrently, he reported the synthesis of benzamides from an aryl iodide, carbon monoxide, a primary amine, and a tertiary amine as base catalyzed by the same type of palladium complex. The related reactions of vinyl halides were also reported, and these reactions occurred with retention of the olefin geometry. ... 

The reactions of aryl halides with carbon monoxide and either alcohols or amines to form esters or amides occur by two related yet distinct mechanistic pathways. These pathways are related to the mechanism of cross coupling presented in Chapter 19, and the reader might find it helpful to refer to the discussion of mechanisms of cross coupling in that chapter. Scheme 17.29 outlines the pathways for the carbonylation of aryl halides to form esters and amides. 

In the absence of hydrogen, a catalytic reaction of carbon monoxide and an alcohol produces alkyl formate (Eq. 7.7). The catalyst involved is an alkali metal alkoxide alone or together with a transition metal carbonyl cluster, e.g. Ru3(CO)i2. ° ... 

The a-keto amides are less susceptible to hydrolysis and preparation of a-keto esters and acids are preferable for synthesizing various derivatives thereof. Various aryl iodides and bromides can be converted into a-keto esters on reactions with alcohols and carbon monoxide in the presence of a base such as tertiary amines or potassium acetate with catalytic amounts of tertiary phosphine-coordinated palladium complexes (Eq. 11).[42]-[46] jjjgjj yields of a-keto esters can be achieved only when iodide substrates are used. Double carbonylation of aryl bromides to a-keto esters can be accomplished with difficulty at much slower rates. Alkyl and benzyl iodides give no double carbonylation products. 

CO. Alkynes will react with carbon monoxide in the presence of a metal carbonyl (e.g. Ni(CO)4) and water to give prop>enoic acids (R-CH = CH-C02H), with alcohols (R OH) to give propenoic esters, RCH CHC02R and with amines (R NH2) to give propenoic amides RCHrCHCONHR. Using alternative catalysts, e.g. Fe(CO)5, alkynes and carbon monoxide will produce cyclopentadienones or hydroquinols. A commercially important variation of this reaction is hydroformyiation (the 0x0 reaction ). 

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