Carbonylations palladium bromide

Excellent examples of metal exchange reactions are provided by complexes of tetraphenylcyclobutadiene. When either iron pentacarbonyl or nickel carbonyl is reacted with tetraphenylcyclobutadiene palladium bromide, the corresponding metal is exchanged with the release of palladium(O) metal. The reaction proceeds only in aromatic solvents and seems to be generally applicable to a variety of transition metal carbonyls. As illustrated in Fig. 6-8, the first step is proposed to involve the formation of uncomplexed tetraphenylcyclobutadiene, a mixed metal halide carbonyl, carbon monoxide. 

Palladium bromide is also an efficient Pd(0) catalyst precursor for the aminocarbonylation of benzyl chlorides (eq 46), car-bonylative Heck reaction of aryl bromides with vinyl ethers (eq 47), and carbonylation of halogenoalkynes (eq 48). ... 

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

Denmark and Kallemeyn have described the mild palladium-catalyzed insertion of 1,2-diethoxy-1,1,2,2,-tetra-methyldisilane EtOMe2SiSiMe2OEt into aryl bromides RBr affording aryldimethylsilyl ethers RMe2SiOEt and Me2SiBrOEt in high yields.750 Williams and Tanaka et al. have reported on the palladium- and platinium-catalyzed reaction of carbonyl and imine compounds with disilanes.7... 

Allyl chlorides and bromides can be carbonylated to afford the respective unsaturated acids and esters with a variety of catalysts under relatively mild conditions such as 30-50 °C and 1 bar CO (Scheme 5.2). Most prominent are the palladium-containing catalysts and both [PdCl2(TPPMS)2] or [PdCl2(TPPTS)2] and [PdCl2(PPh3)2] were used, dissolved in the aqueous and in the organic phases, respectively [14-16]. 

Very high regioselectivities (> 99.5% iso) were obtained, using PdCl2(PhCN)2 in combination with (+)-neomethyldiphenylphosphine and toluene-j9-sulfonic acid, under mild conditions (70 °C and 10 bar). More recently, the palladium-catalyzed alkoxycarbonylation and amido-carbonylation of aryl bromides and iodides in [bmim][BF4] and [bmim][PF6] has been described. Enhanced reaction rates were observed compared to conventional media and the ionic liquid-catalyst could be recycled. 

The brownish-colored solid is air sensitive and should be handled and stored under inert gas atmospheres. Solutions are very air sensitive with precipitation of colloidal palladium. The 31P NMR (109.3 MHz, D20, 5°C) exhibits a singlet at <522.6 ppm. The IR displays the characteristic SO-vibrations at 1225 (sh, vst), 1200 (vst), 1039 (vst), and 622 (vst) cm-1. The compound has been intensively utilized for carbonylation of benzylic chlorides,26 aryl bromides,27 and 5-hydroxymethylfurfural,28 Heck-reactions,29 allylic substitution reactions,30 and oxidations.16... 

Unsymmetricatl ketones can be obtained by the palladium-catalyzed carbonylation of aryl, alkyl and vinyl bromides and iodides in the presence of tetraalkyl- or tetraaryl-tin compounds (equation 113).489,490 The catalyst precursors used were complexes (102), (107) and [PdCI2(AsPh3)2]. 

Since vinylic iodides (and bromides) can be catalytically carbonylated with a palladium catalyst, inter-molecular acylations sometimes can be carried out with appropriate halodienes and carbon monoxide as, for example, is shown in equation (45).107... 

In 2006, the palladium-catalyzed carbonylative [2+2] cycloaddition of allyl bromide with heteroaryliden anilines was reported to afford 2-azetidinones... 

The initial synthetic approach to conivaptan HCl (1) employed by the Yamanouchi discovery group26 commenced with commercially available benzazepinone 10. Acylation of 10 with p-nitrobenzoyl chloride provided benzamide 11. Subsequent hydrogenation of 11 over palladium on carbon yielded aniline 12, which was in turn condensed with biphenyl-2-carbonyl chloride to provide bis(amide) 13. Bis(amide) 13 was subsequently heated with copper(II) bromide in boiling chloroform/ethyl acetate to furnish a-bromoketone 14. It is interesting that condensation of a-bromoketone 14 with acetamidine hydrochloride in the presence of potassium carbonate in boiling acetonitrile afforded not only the desired imidazobenzazepine product (1 53% yield, 2 steps) but also the related oxazolobenzazepine 15 (7% yield, 2 steps), which presumably resulted from nucleophilic attack of the benzazepinone oxygen on the amidine moiety followed by loss of ammonia. Separation of oxazolobenzazepine byproduct 15 from imidazobenzazepine 1 by silica gel chromatography followed by treatment of the purified imidazobenzazepine free-base with hydrochloric acid then provided conivaptan HCl (1). 

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