Bromobenzene, carbonylation

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... 

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). 

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]. 

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... 

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. 

The allylic alcohol substitution reaction may also be carried out in DMF solution with sodium bicarbonate as the base at 100 to 125° with palladium-phosphine catalysts, in which case only carbonyl products are formed. With this catalyst combination nonallylic, unsaturated alcohols also react to form carbonyl compounds in good yields. For example, in an extreme case, 9-decen-l-ol and bromobenzene gave some 10-phenyldecanal (40) ... 

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-... 

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

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. 

On the other hand, arynic reactions are also of interest in the synthesis of benzocyclenones substituted on the aromatic ring by an alkyl group in the ortho position of the carbonyl group. In these syntheses, ortho alkyl bromobenzenes must be used and arynic condensation intermediaries are of the 108 type ... 

Bromobenzene was carbonylated in a biphasic toluene/water system in the presence of Pd(tppts)3 giving the expected benzoic acid exclusively with high conversion [79]. 

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],... 

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