Carbonylation of aryl halides

The palladium-catalyzed carbonylation of aryl halides in the presence of various nucleophiles is a convenient method for synthesizing various aromatic carbonyl compounds (e.g., acids, esters, amides, thioesters, aldehydes, and ketones). Aromatic acids bearing different aromatic fragments and having various substituents on the benzene ring have been prepared from aryl iodides at room temperature under 1 atm 

CO in a mixed solvent of H2O/DMF (1/1 or 1/2, v/v), and even in water alone, depending on the solubility of the substrate (Eq. 6.31)7 The palladium(II) complexes Pd(OAc)2, K2PdCl4, PdCl2(PPh3)2, and Pd(NH3)4Cl2 are used as the precursors of the catalyst, using either K2CO3 or NaOAc as the base. lodoxyarenes can be carbonylated in water alone due to their solubility in the solvent. Recent work has been done on the use of water-soluble catalysts. Under the appropriate pressure and temperature conditions, aryl mercaptans (thiophenols) can also be carbonylated in aqueous media with cobalt carbonyl as the catalyst.  

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The carbonylation of aryl halides under mild conditions in the presence of CsF afford.s the acid fluoride 490 in good yields. Unlike acyl chlorides, acyl fluorides are inert toward Pd(0) catalyst[345]. Benzenesulfonyl chloride (491) undergoes desulfonylation-carbonylation to give the benzoate 492 in the presence of titanium tetralkoxide at 160 °C[346]. 

A number of Pd or Cu catalysts bearing NHC ligands have been prepared for carbonylation of aryl halides. Nacci and co-workers synthesised the benzothiazole carbene ligated Pd complex 32 (Fig. 9.6) and tested it for aryl halide carbonylation... 

Scheme 5. Palladium-catalyzed carbonylations of aryl halides and pseudohalides...

Y. Kayaki, Y. Noguchi, S. Iwasa, T. Ikariya, R. Noyori, An Effitient Carbonylation of Aryl Halides Catalysed by Palladium Complexes with Phosphite Ligands in Supercritical Carbon Dioxide , Chem Commun. 1999, 1235-1236. 

Aryl methyl ketones via the cobalt-catalysed carbonylation of aryl halides (Table 8.16)... 

For the preparation of a-ketoamides, palladium-catalyzed double carbonylation of aryl halides with carbon monoxide and secondary amines is also a useful reaction Kobayashi, T. Tanaka, M. J. Organomet. Chem. 1982, 233, C64 Ozawa, F. Soyama, H. Yamamoto, T. Yamamoto, A. Tetrahedron Lett. 1982, 23, 3383. 

Boyarskii VP (2008) Catalytic systems for carbonylation of aryl halides. Russ J Gen Chem 78(9) 1742-1753... 

Moreover, reaction time was reduced from hours to minutes or even seconds. Indeed, the carbonylation of aryl halides 335 was completed in 10 s to give symmetrical diaryl ketones 336 in excellent yields (Equation (31)). The process optimization to reduce the amount of catalyst disclosed the fact that this carbonylation reaction followed a radical pathway, initiated by the homolytic cleavage of Co2(CO)8 into -00(00)4. It also appeared that the amount of the Oo catalyst had a direct correlation with the internal temperature reached during the reaction. These findings are critical for the development of extremely fast synthesis using carbonylations. 

Catalytic Carbonylation of Aryl Halides in the Presence of Potassium Fluoride General Procedure 33... 

Ikariya and co-workers reported an efficient palladium-catalyzed carbonylation of aryl halides in sc C02 (eq. 2.10) (Kayaki et al., 1999). 2-Iodobenzyl alcohol was converted to the phthalide in the presence of PdCl2L2 [L = PMe3, PPh3, MeCN, P(OEt)3, P(OPh)3, PPh(OMe)2, PPh2(OMe)] with higher rates in sc C02 than in toluene. 

Aromatic carboxylic acids, a,/f-unsaturated carboxylic acids, their esters, amides, aldehydes and ketones, are prepared by the carbonylation of aryl halides and alkenyl halides. Pd, Rh, Fe, Ni and Co catalysts are used under different conditions. Among them, the Pd-catalysed carbonylations proceed conveniently under mild conditions in the presence of bases such as K2CO3 and Et3N. The extremely high toxicity of Ni(CO)4 almost prohibits the use of Ni catalysts in laboratories. The Pd-catalysed carbonylations are summarized in Scheme 3.9 [215], The reaction is explained by the oxidative addition of halides, and insertion of CO to form acylpalladium halides 440. Acids, esters, and amides are formed by the nucleophilic attack of water, alcohols and amines to 440. Transmetallation with hydrides and reductive elimination afford aldehydes 441. Ketones 442 are produced by transmetallation with alkylmetal reagents and reductive elimination. 

C-H bonds in hydrogenation reactions, 276-277 C-Si bonds, 73 Carbonyl complexes, 184 Carbonyl hafnium complex, 144 Carbonylation of aryl halides, 271-272 Carbonylation reactions in ionic liquids, 271... 

As with ester formation, carbonylation of aryl halides under amide-forming conditions and high carbon monoxide pressures leads to synthetically useful yields of a-ketoamides via double carbonylation916- 21. In these reactions the amine must be a fairly strong nucleophile and it is noteworthy that primary amines often give imines as the final product. Aryl chlorides do not normally undergo this reaction but specialized palladium catalysts may facilitate this process890. Alternatively, reaction may be possible via a first-formed... 

Thus, it has been shown that Co(CO)4 ion is a good nucleophile for the catalytic carbonylation of aryl halides in the presence of the electron donor NaH—RONa associate in THF and under photostimulation (equation 113)210. 

A novel method was reported for the carbonylation of aryl halides by cobalt salt catalysts, such as Co(OAc)2, CoCl2, C0SO4, Co(OH)2, Co(OH)3, CoO and Co203 in an aqueous alkaline solution and under irradiation214. 

One of the most interesting applications of the photostimulated carbonylation of aryl halides by Co(CO)4 ions under phase-transfer catalysis conditions is the synthesis of benzolactams and lactones 293 starting from aryl halides bearing amino or hydroxy groups on a side chain ortho to the halogen (equation 180)212. 

Double Carbonylation of Aryl Halides. (DIOP)PdCl2 catalyzed the double carbonylation of phenyl iodide in the presence... 

In contrast, nucleophilic attack at an sp -carbon center with anionic 18-electron species like [Co(CO)4] and [Fe(CO)4] usually fails to activate aromatic or vinylic halides. Thus, catalytic carbonylations of aryl halides are initiated by oxidative addition of a C-X bond to an electronically unsaturated metal complex, normally a palladium [7], cobalt [8] or nickel complex [9]. The rate of this oxidative addition decreases along the sequence... 

The Pd-catalyzed carbonylation of aryl halides (cf Section 2.1.2) occurs with high turnover numbers and reaction rates in SCCO2 as the solvent using standard precursor complexes and commercially available phosphine or phosphite ligands [30]. The generally better performance of the phosphite-based catalysts was attributed to their better solubility in the reaction mixture, but the formation of Pd carbonyl complexes was also mentioned as a possibility. The [Ni(cod)2]/dppb system (dppb = l,4-bis(diphenylphosphino)butane) was investigated in an early study as a catalyst for the synthesis of pyrones from alkynes and CO2 under conditions beyond the critical data of carbon dioxide [31]. Replacing dppb with PMcs results in a system with better solubility and catalytic performance, albeit catalyst deactivation remains a problem [3 c, 15]. 

Some nonconjugated dienes are converted to cyclic ketoesters. 5-Aiyl-1,2,4-oxadiazoles are formed in the carbonylation of aryl halides when RC(=NOH)NH2 are present. 

Reductive carbonylations of aryl halides to benzaldehydes, amidocarbonylations, and double carbonylations of C—X bonds are of interest in industry. 

The carbonylation of aryl halides with alcohols and amines catalysed by palladium complexes with triphenylphosphine ligand is the convergent and direct route to the synthesis of aromatic esters as well as aromatic amides. Even though these palladium complexes are widely employed as the best catalytic system, those catalysts are difficult to separate and reuse for the reaction without further processing. The major drawbacks are oxidation of triphenylphosphine to phosphine oxide, reduction of palladium complex to metal and termination of the catalytic cycle. The phosphine-free, thermally stable and air resistant catalyst (1) containing a carbon-palladium covalent bond (Figure 12.3) has been found to be a highly selective and efficient catalyst for the carbonylation of aryl iodides.[1]... 

Reaction medium. By virtue of its attributes supercritical carbon dioxide deserves its increasing applications as a reaction medium in synthesis. These include epoxidation" with oxygen and PhCHO, rhodium-catalyzed hydroboration, Pd(0)-catalyzed 1,4-hydroarylation of enones" and Heck reaction in the presence of Pd-C," carbonylation of aryl halides, Glaser coupling of 1-alkynes (mediated by CuCy using a solid ba.se (NaOAc)," as well as seandium(III) perfluorooctanesulfonate-catalyzed Diels-Alder and hetero-Diels-Alder reaetions. ... 

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