Carbonylation of organic halides

When aqueous NaOH is given as a base, isomerization of the product butenoic acids can be extensive depending on the nature and concentration of base. In dilute aqueous solutions alcohols do not react to form the respective esters, however, the reactions are strongly accelerated due to the increased solubility of the substrates in the catalyst-containing aqueous-alcoholic phase. For example, with 23-33 % (v/v) ethanol in water the [PdCl2(TPPTS)2]-catalyzed hydroxycarbonylation of allyl chloride proceeded with TOF-s of 1850-2400 if1 and with a vinylacetic/crotonic acid ratio of 21 [16]. Addition of [CuCl2] increased the overall conversion rate (by a factor of 2 at [Cu]/[Pd] = 8) but at the same time the side reactions 

In the carbonylation of allyl halides the highly toxic [Ni(CO)4] catalyst could be replaced by [Ni(CN)2], which yielded [Ni(CN)(CO)3] under the reaction conditions [17]. The cyanotricarbonylnickel(O) anion is a versatile catalyst of carbonylations under phase transfer conditions [18], however, hydroxycarbonylation of allyl chloride proceeds effectively without PT catalysts in a genuine biphasic system, as well. 

Organic phase heptane, benzene, anisole, butanol o-xylene toluene o-xylene toluene toluene benzene 

An exceptionally simple procedure was developed for the catalytic carbonylation of chloroarenes using [PdCl2(PCy3)] as catalyst. According to this method the neat chloroarene, e.g. m-chlorotoluene and the catalyst are stirred with 20 % (w/w) aqueous KOH at reflux temperature with bubbling CO. The benzoic acids are extracted from the aqueous phase after 

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CARBONYLATION OF ORGANIC HALIDES 6.6.1 Carbonylation of Alkyl Halides... 

The utility of SCFs is not limited to organotransi-tion metal chemistry. scC02 is a promising medium for free-radical carbonylation of organic halides to ketones or aldehydes. As shown in Figure 15A, the... 

Carbon monoxide and low valent transition metals are known to give various quite well described complexes. However, due to the strong coordination to CO, these metal carbonyl compounds are not very reactive towards carbon-halogen bonds. Thus the carbonylation of organic halides remains a difficult reaction since the presence of CO leads to the deactivation of the catalytic system. Various attempts to overcome this drawback have however been reported. 

The mechanism of palladium-catalyzed carbonylation of organic halides is generally assumed to involve oxidative additon of R-X to a Pd(0) species which is formed from the precursors on the action of CO + OH . Migratory insertion of R onto a coordinated CO followed by reaction with a nucleophile generates the product and gives back the catalytically active palladium(O) species (Scheme 5.4 A). 

Skoda-Foldes R, Kollar L (2002) Synthetic applications of palladium catalysed carbonylation of organic halides. Curr Org Chem 6(12) 1097-1119... 

Amides are produced from the palladium-catalyzed carbonylation of organic halides if primary or secondary amines are present rather than only an alcohol (/5) ... 

A brief review on the palladium-catalyzed carbonylation of organic halides has appeared.505... 

R. Skoda-Foldes, L. Kollar, Synthetic Applications of Palladium Catalyzed Carbonylation of Organic Halides, Curr. Org. Chem. 2002, 6, 1097-1119. 

The carbonylation of reactive organic substrates, up to now, has been the most applied and investigated aspect of CO catalysis because of its large industrial applications [1 ]. We shall limit our discussion to the carbonylation of unsaturated hydrocarbons, since the direct carbonylation of organic halides, or similar activated organic derivatives, has implications that are mainly limited to fine chemical production (with the exception of methanol) [2,3. ... 

The area of donble carbonylation has been recently reviewed by des Abbayes and Salaiin. Both stoichiometric and catalytic systems are snrveyed, covering monometallic complexes of Co, Pd, Fe and Ni, althongh the main emphasis is on catalytic monometallic systems of Co and Pd with a variety of snbstrates (amines, alcohols, organic halides). A general scheme for the donble carbonylation of organic halides with a palladium is shown below (Scheme 29). 

The possibility of the carbonylation of organic halides under PTC conditions was demonstrated for the first time in 1976 [110], Benzyl chloride was transformed to phenylacetic acid in a xylene/aq. NaOH system containing a Pd° complex and a PT catalyst. Metal carbonyls are the most frequently used carbonylation catalysts. The effectiveness of Co2(CO)g for the PTC carbonylation of benzyl halides was discovered independently by two research groups [111, 112]. Under mild conditions, benzyl halides are converted into carboxylic acids (eq. (8)). 

The palladium-catalyzed carbonylation of organic halides is a convenient means of synthesizing carbonyl compounds. For example, the single carbonylation of aryl iodides has been applied to synthesize lactones and lactams (eq (69) and (70)) [97,98],... 

The hydroxycarbonylations (carboxylations) of alkyl, aryl, benzyl and allyl halides are from a retrosynthetic and mechanistic standpoint closely related. This type of reaction is widely used in organic synthesis [6], although a stoichiometric amount of salt by-product makes these methods less attractive on a large scale. The use of water-soluble catalysts for carbonylation of organic halides was scarcely studied in the past. Up to now palladium, cobalt, and nickel compounds in combination with water-soluble ligands have been used as catalysts for various carboxylations. 

Cassar, L., M. Foa, and A. Gardano, The Use of Phase Transfer Catalysis in Palladium-Catalyzed Carbonylation of Organic Halides, J. Organomet. Chem, 121, C55 (1976). 

PTC and Metal Complexes Catalyzed Carbonylation of Organic Halides... 

Carbonylation of organic halides catalyzed by transition metals is a general and efficient method for manufacturing carboxylic acids. PTC offers particularly convenient conditions for this reaction ... 

Carbonylation of organic halides. This reaction can be conducted under phase-transfer conditions ... 

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