Carbonylation of bromobenzene

Carbonylation of bromobenzene (Scheme 5.7) with [Pd(TPPTS)3] required still higher temperatures (150 T). The possible acyl intermediates of such reactions [PdBr(C6H5CO) Ph3)2] and [PdBr(C6H5CO)(TPPTS)2] were synthetized and characterized [26]. Bromobenzene was also carbonylated to benzoic acid in water/toluene using a catalyst prepared from [PdCl2(COD)j and 27 in the presence of NEt3 [21]. 

Attempted reductive carbonylation of bromobenzene with CO/H2 or with CO/HCOONa in the presence of a Pd/tppts catalyst failed to afford any benzaldehyde 464... 

The carbonylation of bromobenzene with palladium/tppts complexes was reported by Monteil and Kalck (81). Some of the aforementioned disadvantages were alleviated in a new process for carbonylation of substituted benzyl chlorides (82). The reaction was carried out in a two-phase system in the presence of CO at atmospheric pressure yields of phenylacetic acids of 80-94% were reported. The palladium catalyst contains tppts or BINAS-Na, 10, to allow water solubility. The maximum turnover frequency was found to be 135 h 1, and the lifetime of the catalyst increased as a result of continuous addition of reactants. 

Scheme 9.12 Carbonylation of bromobenzene with a palladium-carbene catalyst...

Halobi(triphenylphosphine)phenylnickel(II) complexes as catalysts were also tested for the reductive carbonylation of bromobenzene and iodobenzene by the same authors. The yield of benzaldehyde based on iodobenzene was only 20 % at 100 °C using triethylamine (NEta) as its base. Bromobenzene did not react under the usual conditions, and a stoichiometric reaction with chlorobi(triphenylphos-phine)phenylnickel gave only benzene and biphenyl at 100 °C. One decade later,... 

Monteil, F. Kalck, P. ( 1994) Carbonylation of bromobenzene in a biphasic medium catalyzed by water-soluble palladium complexes derived from tris(3-sulphophenyl)phos-phine, / Organomet. C/ ew., 482,45-51. 

Lactones and lactams have also be prepared by the carbonylation of 2-(co-hydroxy-alkyl)- and 2-(co-aminoalkyl)bromobenzenes [29] (see Section 8.3). 

As for aliphatic ketones, two moles of starting carbonyl compound per mole of bromobenzene must be used. However, unreacted starting material is also generally easily recovered. 

Palladium complexes of TPPTS and TPPMS have been employed extensively as catalysts for carbonylation, hydroxycarbonylation, and C—C cross-coupling reactions (cf. Section 6.6). Hydroxycarbonylation of bromobenzene in biphasic medium using Pd(TPPTS)3 as catalyst yields benzoic acid, which remains in the aqueous phase, thus avoiding the direct recycling of the catalyst [59]. The formation of Pd(TPPTS)3 from PdCl2 and TPPTS in aqueous solution has been studied in detail by 170, 1H 31P, and 35C1 NMR spectroscopy. The complex [ PdCI(TPPTS)3 Cl obtained initially is reduced by excess TPPTS, TPPTSO being formed. A more attractive synthesis of Pd(TPPTS)3 involves the facile reduction of [PdCl-(TPPTS)3]+C1- with CO (Scheme 1) [60],... 

It has been found that treatment of propiophenone with an excess amount of bromobenzene gives rise to l,2,3-triphenyl-2-propen-l-one (Eq. 11) [43]. In this reaction, a-arylation, unsaturation via -hydrogen elimination, and Heck-type arylation occur successively. From the reaction of butyrophenone is obtained the corresponding triarylated product (Eq. 12). The reaction sequence involves a-arylation, unsaturation via p-hydrogen elimination, two times vinyl-ogous arylation (y-arylation), and double bond isomerization. It should be noted that a,p-unsaturated carbonyl compounds are generally arylated at their y position (Eqs. 13 and 14) [54-56]. 

Tanaka and his associates demonstrated for the first time how to use non-volatile ionic liquids (ILs) as solvents in palladium-catalyzed carbonylations [163], In the case of alkoxycarbonylation of bromobenzene, higher yields were obtained when 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] was used as the reaction medium compared with standard conditions. And the selectivity for the monocarb-onylation of iodobenzene with t -PrOH or Et2NH was significantly enhanced by [bmim][BF4]. After separation of the products, the solvent-catalyst system was easily recycled and exhibited catalytic activity up to seven times. Since then the replacement of traditional solvents with quaternary ammonium halides, imidazoli-um- or pyridinium-derived ILs has gained increasing importance [164—173]. Recently, the phosphonium salt IL trihexyl(tetradecyl)phosphonium bromide has proven to be an effective reaction medium for various carbonylation reactions of aryl and vinyl bromides or iodides under mild conditions (Scheme 2.17) [174]. 

The first report on a palladium-catalyzed carbonylative C-H activation was published in 1986 by Kobayashi and Tanaka [1]. They reported that the carbonylation of organic halides with activated methylene compounds in the presence of NEta under 20 bar of CO produces various ketones in good yields (Scheme 6.1). Aryl iodides, bromobenzene and one example of a vinyl bromide were used as starting materials. But relatively high pressure and high pressure are needed, and tri-ethylamine was used both as a base and solvent. 

The thermal decomposition of thia2ol-2-yl-carbonyl peroxide in benzene, bromobenzene, or cumene affords thiazole together with good yields of 2-arylthiazoles but negligible amounts of esters. Thiazol-4-ylcarbonyl peroxide gives fair yields of 4-arylthiazoles, but the phenyl ester is also a major product in benzene, indicating reactions of both thiazol-4-yl radicals and thiazol-4-carbonyloxy radicals. Thiazole-5-carbonyl peroxide gives... 

As the last example of C-C bond-formation reactions catalyzed by alkaline earth hydroxides, we mention the recently reported a-arylation of diethyl malonate in the presence of a palladium catalyst and a base in a separate phase 299). The arylation of carbonyl compounds is a carbon-carbon coupling reaction between an aryl halide and an enolate, which is usually catalyzed by palladium salts in the presence of an appropriate base (300,301). The arylation of diethyl malonate with bromobenzene (Scheme 48) was performed with tetrachloropalladate as the... 

Kato et al. (123) also found that isomtinchnone 51a reacts with tropone (251) to afford 252, which is apparently the hrst example of a [47i+6ti] cycloadduct involving both a mesoionic heterocycle and a carbonyl ylide (Scheme 10.34). The one-pot reaction of 253 gave 252 in somewhat higher yield. Whereas heating the latter in bromobenzene affords o-benzoylmandelanilide (69%), heating 252 in refluxing toluene in the presence of DMAD leads to furan 254. 

Problem 13.11 For the following pairs of halides and carbonyl compounds, give the structure of each alcohol formed by the Grignard reaction, (a) Bromobenzene and acetone, (b) p-Chlorophenol and formaldehyde, (c) Isopropyl chloride and benzaldehyde. (d) Chlorocyclohexane and methyl phenyl ketone. 4... 

In the reaction of allylic alcohols, elimination of /1-hydrogen from an OH-bearing carbon takes place to give saturated carbonyl compounds, rather than arylated allylic alcohols [25,26]. The reaction of methallyl alcohol (43) with bromobenzene affords a-... 

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