Aryl halides carbonylation

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 9.6 General scheme for aryl halide carbonylation...

Aryl halides, carbonylation of, 271-272 Arylboronates, synthesis of, 223-226 Arylsilanes, dehydrocoupling, 21... 

Aryl Halide Carbonylations. Palladium-catalyzed carbony-lation of aryl halides is an efficient way to produce carboxylic acid derivatives. Aminocarbonylation of aryl chlorides has heen performed using Mo(CO)6 as the carbon monoxide source and a catalyst derived from TTBHBF4 andpalladacycle 1 under microwave irradiation (170 °C). Tbe catalyst system was also applied to the carbonylation of 4-chloro-l-trifluoromethylbenzene in hutanol to... 

As with malonate, the two strong electron-withdrawing functional groups of cyanoacetate significantly enhance the acidity of the methylene group. Accordingly, it can be readily deprotonated and the anion reacts with abroad spectrum of electrophiles, such as alkyl and activated aryl halides, carbonyl compounds, a,/3-unsaturated carbonyl or carboxyl derivatives, and nitrous acid. 

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]. 

The o-keto ester 513 is formed from a bulky secondary alcohol using tricy-clohexylphosphine or triarylphosphine, but the selectivity is low[367-369]. Alkenyl bromides are less reactive than aryl halides for double carbonyla-tion[367], a-Keto amides are obtained from aryl and alkenyl bromides, but a-keto esters are not obtained by their carbonylation in alcohol[370]. A mechanism for the double carbonylation was proposed[371,372],... 

The 2-substituted 3-acylindoles 579 are prepared by carbonylative cycliza-tion of the 2-alkynyltrifluoroacetanilides 576 with aryl halides or alkenyl tri-flates. The reaction can be understood by the aminopalladation of the alkyne with the acylpalladium intermediate as shown by 577 to generate 578, followed by reductive elimination to give 579[425]. 

The reaction of the 1- and (2-ethoxyvinyl)tributylstannanes (721) and (723) as masked carbonyls with aryl halides proceeds smoothly and the products 722 and 724 are used for further reactions[592,593]. 

By reaction with the appropropriate aryl halides can be prepared a variety of aryltin compounds that are not accessible from the reactions involving arylmagnesium halides and organotin halides (88,89) there is evidence that an aryne intermediate may be involved (90). However, for some purposes, such as the addition to carbonyl compounds, ox-iranes, and oxetanes, to give hydroxyalkyltin compounds, the Sn-Mg reagents may have advantages (see Section II,E) (91-93). 

In certain cases, Michael reactions can take place under acidic conditions. Michael-type addition of radicals to conjugated carbonyl compounds is also known.Radical addition can be catalyzed by Yb(OTf)3, but radicals add under standard conditions as well, even intramolecularly. Electrochemical-initiated Michael additions are known, and aryl halides add in the presence of NiBr2. Michael reactions are sometimes applied to substrates of the type C=C—Z, where the co-products are conjugated systems of the type C=C—Indeed, because of the greater susceptibility of triple bonds to nucleophilic attack, it is even possible for nonactivated alkynes (e.g., acetylene), to be substrates in this... 

This method ensures the deposition of very reactive metal nanoparticles that require no activation steps before use. We shall review here the following examples of catalytic reactions that are of interest in line chemical synthesis (a) the hydrogenation of substituted arenes, (b) the selective hydrogenation of a, 3-unsaturated carbonyl compounds, (c) the arylation of alkenes with aryl halides (Heck reaction). The efficiency and selectivity of commercial catalysts and of differently prepared nanosized metal systems will be compared. 

The direct preparation of arylboronic esters from aryl halides or triflates now allows a one-pot, two-step procedure for the synthesis of unsymmetrical biaryls (Scheme 1-41) [147]. The synthesis of biaryls is readily carried out in the same flask when the first coupling of the triflate with diboron 82 is followed by the next reaction with another triflate. The synthesis of naturally occurring biflavanoids and the couphng of N-(phenylfluorenyl)amino carbonyl compounds to polymeric supports are reported [154]. 

Coupling of organostannanes with halides in a carbon monoxide atmosphere leads to ketones by incorporation of a carbonylation step.249 The catalytic cycle is similar to that involved in the coupling of alkyl or aryl halides. These reactions involve Reactions involving a migration of one of the organic substituents to the carbonyl carbon, followed by... 

Nickel carbonyl is an extremely toxic substance, but a number of other nickel reagents with generally similar reactivity can be used in its place. The Ni(0) complex of 1,5-cyclooctadiene, Ni(COD)2, can effect coupling of allylic, alkenyl, and 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... 

Transition metal-catalyzed transformations are of major importance in synthetic organic chemistry [1], This reflects also the increasing number of domino processes starting with such a reaction. In particular, Pd-catalyzed domino transformations have seen an astounding development over the past years with the Heck reaction [2] - the Pd-catalyzed transformation of aryl halides or triflates as well as of alkenyl halides or triflates with alkenes or alkynes - being used most often. This has been combined with another Heck reaction or a cross-coupling reaction [3] such as Suzuki, Stille, and Sonogashira reactions. Moreover, several examples have been published with a Tsuji-Trost reaction [lb, 4], a carbonylation, a pericyclic or an aldol reaction as the second step. 

Extension to carbocyclization of butadiene telomerization using nitromethane as a trapping reagent is reported (Eq. 5.48).72 Palladium-catalyzed carbo-annulation of 1,3-dienes by aryl halides is also reported (Eq. 5.49).73 The nitro group is removed by radical denitration (see Section 7.2), or the nitroalkyl group is transformed into the carbonyl group via the Nef reaction (see Section 6.1). 

Hydroxycarbonylation and alkoxycarbonylation of alkenes catalyzed by metal catalyst have been studied for the synthesis of acids, esters, and related derivatives. Palladium systems in particular have been popular and their use in hydroxycarbonylation and alkoxycarbonylation reactions has been reviewed.625,626 The catalysts were mainly designed for the carbonylation of alkenes in the presence of alcohols in order to prepare carboxylic esters, but they also work well for synthesizing carboxylic acids or anhydrides.137 627 They have also been used as catalysts in many other carbonyl-based processes that are of interest to industry. The hydroxycarbonylation of butadiene, the dicarboxylation of alkenes, the carbonylation of alkenes, the carbonylation of benzyl- and aryl-halide compounds, and oxidative carbonylations have been reviewed.6 8 The Pd-catalyzed hydroxycarbonylation of alkenes has attracted considerable interest in recent years as a way of obtaining carboxylic acids. In general, in acidic media, palladium salts in the presence of mono- or bidentate phosphines afford a mixture of linear and branched acids (see Scheme 9). 

A set of aryl halides was reacted with carbonyl hydrazides and molybdenum hexacar-bonyl [Mo(CO)6] as a source of carbon monoxide, employing fluorous triphenylphos-phine (F-TPP) as ligand and the perfluorocarbon liquid FC-84 as a perfluorinated solvent (Scheme 7.87 see also Scheme 6.46c). 

The palladium-catalyzed Heck carbonylation reaction is a powerful means of generating amides, esters, and carboxylic acids from aryl halides or pseudohalides [28]. The development of rapid, reliable, and convenient procedures for the introduction of carbonyl groups is important for the development of high throughput chemistry in general and high-speed microwave-mediated chemistry in particular. Unfortunately, the traditional method of introducing carbon monoxide into a reaction mixture via a balloon or gas tube is not practical because of the special requirements of microwave synthesis. 

Muller and co-workers reported the three-component one-pot synthesis of various pyrimidines through the in situ generation of unsaturated carbonyl compounds. The palladium catalyzed coupling of aryl halides bearing electron withdrawing substituents 7 with propargyl alcohols 8 produced unsaturated carbonyl compounds 9 after isomerization, which condensed with amidines 10 to form triaryl pyrimidines 11 . 

More recently, we have been engaged in mechanistically related car-bonylations of aryl halides (Klaus et al. 2006). As demonstrated in Scheme 5, such reactions offer numerous possibilities for the selective synthesis of aromatic carbonyl compounds. 

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

The palladium-catalyzed arylations of aromatic carbonyl compounds such as ketones,67,67a amides (Equation (60)),68 and aldehydes69 with aryl halides and triflates give the multiple arylation products similarly. 

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. 

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