Acid chlorides palladium complexes

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

A palladium catalyst with a less electron-rich ligand, 2,2-dipyridyl-methylamine-based palladium complexes (4.2), is effective for coupling of aryl iodides or bromides with terminal alkynes in the presence of pyrrolidine and tetrabutylammonium acetate (TBAB) at 100°C in water.37 However, the reactions were shown to be faster in NMP solvent than in water under the reaction conditions. Palladium-phosphinous acid (POPd) was also reported as an effective catalyst for the Sonogashira cross-coupling reaction of aryl alkynes with aryl iodides, bromides, or chlorides in water (Eq. 4.18).38... 

Recently, the groups of Fu and Buchwald have coupled aryl chlorides with arylboronic acids [34, 35]. The methodology may be amenable to large-scale synthesis because organic chlorides are less expensive and more readily available than other organic halides. Under conventional Suzuki conditions, chlorobenzene is virtually inert because of its reluctance to oxidatively add to Pd(0). However, in the presence of sterically hindered, electron-rich phosphine ligands [e.g., P(f-Bu)3 or tricyclohexylphosphine], enhanced reactivity is acquired presumably because the oxidative addition of an aryl chloride is more facile with a more electron-rich palladium complex. For... 

Several groups intercepted the indole-palladium complex that is initially obtained on cyclization by a subsequent Heck reaction. As will be seen, this can be a powerful elaboration of indoles. In the first example of this concept, Utimoto and co-workers ambushed intermediate 354 with a series of allylic chlorides to give 355. Normal acid workup yields the corresponding C-3 unsubstituted indoles (52-83%) [310]. 

Aromatic acid chlorides are converted into the corresponding anhydrides in high yields (>95%), when reacted with carbon monoxide under solid liquid basic catalysed conditions in the presence of a complexed cobalt or palladium salt [6]. In the absence of the quaternary ammonium salt, only hydrolysis to the carboxylic acid occurs. 

Although several Lewis Acids were evaluated, including titanium(lV) chloride, aluminum(lll) chloride and tin(lV) chloride, ferric(lll) chloride proved to be the most effective co-catalyst. We believe that in the presence of a Lewis Acid, the rate of j3-palladium hydride elimination (H-Pd-X) from the -allyl carbomethoxy palladium complex 4 can be enhanced. A good leaving group such as iodide attached to -allyl carbomethoxy palladium complex 4 would facilitate iodopalladium hydride elimination to selectively form methyl, -pentadienoate (Equation 11.). 

One of the first compounds to be introduced to the clinic, aztreonam (40-9), has been produced by total synthesis. Constmction of the chiral azetidone starts with amide formation of L-threonine (40-1) via its acid chloride treatment with ammonia leads to the corresponding amide (40-2). The primary amino group in that product is then protected as its carbobenzyloxy derivative (40-3). Reaction of that product with methanesulfonyl chloride affords the mesylate (40-4). Treatment of that intermediate with the pyridine sulfur trioxide complex leads to the formation of the A -sulfonated amide (40-5). Potassium bicarbonate is sufficiently basic to ionize the very acidic proton on the amide the resulting anion then displaces the adjacent mesylate to form the desired azetidone the product is isolated as its tetrabutyl ammonium salt (40-6). Catalytic hydrogenation over palladium removes the carbobenzyloxy protecting group to afford the free primary amine (40-7). The... 

Reaction of siloxycyclopropane 1 with acid chlorides in the presence of a palladium catalyst also proceeds cleanly to give 4-ketoesters in high yields (Eq. 59, Table 14) [57]. Chloroform is a suitable solvent. Kinetic studies have revealed that the interaction between 1 and an acylpalladium chloride complex is the rate limiting step. 

In new studies heteropoly acids as cocatalysts were found to be very effective in combination with oxygen in the oxidation of ethylene.1311 Addition of phosphomo-lybdic acid to a chloride ion-free Pd(II)-Cu(II) catalyst system results in a great increase in catalytic activity and selectivity.1312 Aerobic oxidation of terminal alkenes to methy ketones can be performed with Pd(OAc)21313 or soluble palladium complexes. Modified cyclodextrins accelerates reaction rates and enhance selectivities in two-phase systems under mild conditions.1315 1316... 

Dicarboxylic acids form monomeric complexes with palladium(II), K2[Pd(X2)2] (X2 = oxalate, malonate, etc,).153154 They may be prepared by warming a suspension of palladium(II) chloride with a concentrated solution of the alkali metal dicarboxylate or by using other palladium complexes containing readily substituted ligands such as [Pd(OH)2], [Pd(N03)2(H20)2] or [Pd(02CMe)2]3-155 These complexes are claimed to have useful antitumour properties.155 Complexes [Pd(X2)L2] (X2 = dicarboxylate L = amine or L2 = diamine) may be prepared by reaction of the dichloro complex with a carboxylate salt.156,128... 

Hydrocarboxylation of Polyunsaturated Fatty Acids and Esters with a Palladium Chloride— Triphenylphosphine Complex Catalyst... 

Mechanistic studies (ref. 6, 7) suggest the intermediacy of a zerovalent palladium complex produced by reductive elimination of an acid chloride, and the need for hydrogen chloride in order to cleave the C-OMe bond by preliminary protonation of the methoxy group leading to an allylpalla-dium complex which undergoes carbonylation (Scheme 1). 

Normally, the most practical vinyl substitutions are achieved by use of the oxidative additions of organic bromides, iodides, diazonium salts or triflates to palladium(0)-phosphine complexes in situ. The organic halide, diazonium salt or triflate, an alkene, a base to neutralize the acid formed and a catalytic amount of a palladium(II) salt, usually in conjunction with a triarylphosphine, are the usual reactants at about 25-100 C. This method is useful for reactions of aryl, heterocyclic and vinyl derviatives. Acid chlorides also react, usually yielding decarbonylated products, although there are a few exceptions. Likewise, arylsulfonyl chlorides lose sulfur dioxide and form arylated alkenes. Aryl chlorides have been reacted successfully in a few instances but only with the most reactive alkenes and usually under more vigorous conditions. Benzyl iodide, bromide and chloride will benzylate alkenes but other alkyl halides generally do not alkylate alkenes by this procedure. 

Carboxylic acid chlorides and chloroformate esters add to tetrakis(triphenylphosphine)palladium(0) to form acylpalladium derivatives (equation 42).102 On heating, the acylpalladium complexes can lose carbon monoxide (reversibly). Attempts to employ acid halides in vinylic acylations, therefore, often result in obtaining decarbonylated products (see below). However, there are some exceptions. Acylation may occur when the alkenes are highly reactive and/or in cases where the acylpalladium complexes are resistant to decarbonylation and in situations where intramolecular reactions can form five-membered rings. 

The use of ligand exchange has been examined for the analysis of PTH (phenylthio-hydantoin) amino acids separated on silica gel plates [92]. The method is an extension of the procedure developed for organophosphate pesticides [84]. The chromatoplate is sprayed with a solution of palladium(II) chloride and calcein. Palladium complexes with calcein to form a non-fluorescent chelate. However, in the presence of many sulfur-containing compounds, such as PTH-amino acids, the palladium is displaced from the complex liberating free calcein which gives an intense fluorescence. This method is capable of determining 0.1-nmole amounts of PTH-amino acids. 

Parrish and Buchwald30 performed couplings with a polystyrene-supported biphenyl-phosphine palladium complex between aryl halides and either amines (entry 24) or boronic acids (entry 25). The resin-bound complex is analogous to the corresponding homogeneous compound and is effective for couplings to unactivated aryl halides, including aryl chlorides. The complex is air-stable and retains activity after recovery without apparent loss of palladium. 

With this end in view, phenyldimcthylsilyl tri-n-butylstannane was added under the influence of zero-valent palladium compound with high regioselectivity and in excellent yield to the acetylene 386 to give the metallated olefin 387 (Scheme 56). The vinyl lithium carbanion 388 generated therefrom, was then converted by reaction with cerium(lll) chloride into an equilibrium mixture (1 1) of the cerium salts 389 and 390 respectively. However, the 1,2-addition of 389 to the caibonyl of 391, which in principle would have eventually led to ( )-pretazettine, did not occur due to steric reasons — instead, only deprotonation of 391 was observed. On the other hand, 390 did function as a suitable nucleophile to provide the olefinic product 392. Exposure of 392 to copper(II) triflate induced its transformation via the nine membered enol (Scheme 55) to the requisite C-silyl hydroindole 393. On treatment with tetrafluoroboric acid diethyl ether complex in dichloromethane, compound 393 suffered... 

A remarkable modular approach to polyfunctionalized pyrroles has also been developed by Arndtsen. A new palladium complex 162 was designed to catalyze this useful reaction, which combines four components an inline, an acid chloride, an alkyne, and carbon monoxide (Scheme 8.72) [151]. A working mechanism proposed by the authors is presented in Scheme 8.73. 

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