Palladium acetate, catalyzed amination

The transformations in Table 2 illustrate that palladium(0)-catalyzed aminations proceed much faster for allyl chlorides than for allyl esters. The chloro acetates, readily available by diastereoselective palladium(II)-catalyzed 1,4-functionalization of 1,3-dienes27, thus give rise to the amino acetates in a highly chemo-, regio-, and diastereoselective fashion28-30. 

Table 2. Palladium(0)-Catalyzed Aminations of Chloro Acetates" b,c...

Oxidative Amination of Alkenes. Palladium acetate-catalyzed aerobic oxidation of cyclopentene and cyclooctene using TcesNH2 affords the corresponding allylic amine products (eq 8). Small amounts of isomeric alkene products are also obtained in this reaction. 

The Suzuki reaction has been successfully used to introduce new C - C bonds into 2-pyridones [75,83,84]. The use of microwave irradiation in transition-metal-catalyzed transformations is reported to decrease reaction times [52]. Still, there is, to our knowledge, only one example where a microwave-assisted Suzuki reaction has been performed on a quinolin-2(lH)-one or any other 2-pyridone containing heterocycle. Glasnov et al. described a Suzuki reaction of 4-chloro-quinolin-2(lff)-one with phenylboronic acid in presence of a palladium-catalyst under microwave irradiation (Scheme 13) [53]. After screening different conditions to improve the conversion and isolated yield of the desired aryl substituted quinolin-2( lff)-one 47, they found that a combination of palladium acetate and triphenylphosphine as catalyst (0.5 mol %), a 3 1 mixture of 1,2-dimethoxyethane (DME) and water as solvent, triethyl-amine as base, and irradiation for 30 min at 150 °C gave the best result. Crucial for the reaction was the temperature and the amount of water in the... 

Reduction of iV-(3-bromopropyl) imines gives a bromo-amine in situ, which cyclizes to the aziridine. Five-membered ring amines (pyrrolidines) can be prepared from alkenyl amines via treatment with N-chlorosuccinimide (NCS) and then BusSnH. " Internal addition of amine to allylic acetates, catalyzed by Pd(PPh3)4, leads to cyclic products via a Sn2 reaction. Acyclic amines can be prepared by a closely related reaction using palladium catalysts. Three-membered cyclic amines (aziridines)... 

The second coupling component, 6-aminocarbazole 1082, was prepared starting from the same known O-tosylate 1063 (165,665). Thus, Buchwald-Hartwig palladium-catalyzed amination of 4-bromonitrobenzene (1076) with 1063 afforded the diaryla-mine 1077. Treatment of 1077 with an excess of Pd(OAc)2 in acetic acid led to the carbazole 1078 in 53% yield. After protection of the carbazole nitrogen with a 2-trimethylsilylethoxymethyl (SEM) group, the product 1079 was subjected to alkaline... 

Palladium catalysts that are free of halide ions effect the dimerization and carboxylation of butadiene to yield 3,8-nonadienoate esters. Palladium acetate, solubilized by a tertiary amine or an aromatic amine, gives the best yields and selectivities (equation 57).87 Palladium chloride catalyzes the hydrocarboxylation to yield primarily 3-pentenoates.88 The hydrocarboxylation of isoprene and chloroprene is regio-selective, placing the carboxy function at the least-hindered carbon (82% and 71% selectively) minor amounts of other products are obtained (equation 58). Cyclic dienes such as 1,3-cyclohexadiene and 1,3-cyclooctadiene are similarly hydrocarboxylated. 

Palladium acetate triarylphosphine complexes catalyze the addition of vinylic groups from vinylic halides to olefinic compounds in the presence of amines. Conjugated dienes are major products from 0,/3-unsaturated acids, esters, or nitriles while unactivated olefinic compounds react best in the presence of secondary amines where allylic amines are major products. The reactions are usually regio- and stereospecific. The synthetic utility of the reaction is illustrated with a wide variety of examples. 

This palladium-catalyzed three-component coupling reaction leading to the formation of aryl-substituted allylic amines was recently adapted to solid-phase synthesis (Scheme 8.23). Amines were chosen to attach to a solid support (Rink resin) in this three-component coupling process and were reacted with a variety of aryl halides and linear or cyclic non-conjugated dienes, the reaction being carried out at 100 °C for two days in the presence of palladium acetate and diisopropylethyl-amine. A wide variety of aryl-substituted allylic amines were then obtained after cleavage from the solid support by trifluoroacetic acid [60],... 

Scheme 3 Asymmetric allylic amination of l,3-diphenyl-l-propene-3-acetate catalyzed by Pyrphos-palladium complexes...

Azide 190, available through palladium-catalyzed amination of the corresponding cyclohex-2-enyl acetate with azonane, can be sequentially reduced and hydrolyzed to produce amino acid 191 (Equation 11) <2000BML1257>. 

Three-component additions, comprising two conjugated diene molecules and a nucleophile, can be catalyzed by palladium salts, such as palladium acetate. The major products are 1-substituted 2,7-octadienes, along with minor amounts of 3-substituted 1,7-octadienes (equation 65). Water, alcohols, phenols, carboxylic acids, and amines are some of the nucleophiles that have been used in this reaction. 

The performance of metal-catalyzed reactions in aqueous media is an attractive concept, for the ecological and economic benefits, which could arise. This concept was tested for PPEs by Li et al. ° They treated p-diiodobenzene, 4,4 -diiodobiphenyl, or 1,4-diiododurene (1,4-diiodotetramethylbenzene) with acetylene gas in a mixture of acetonitrile, triethyl-amine, and water. As coupling catalyst the authors utilized a mixture of palladium acetate, triphenylphos-phine, and Cul. The resulting polymers however were insoluble and of low molecular weight. 

Carbamates and ureas are easily prepared and separated from the oxidative carbonylation of amines catalyzed by [PdCl2(phenanthroline)] dissolved in [G4GiIm]BF4. The carbonylation of terminal 3-alkyn-l-ols and l-alkyn-4-ols by palladium acetate/2-(diphenylphosphino)pyridine dissolved in [G4CiIm]PF6 or [C4CiIm]BF4 affords quantitatively and selectively v< -a-methylene (Scheme 21) and 7- and -lactones, respectively. ... 

The first palladium-catalyzed carbonylations of aryl halides were published in 1974 and 1975 (Equation 17.59). ° Heck first reported the synthesis of benzoates by the reaction of an aryl iodide, carbon monoxide, and an alcohol in the presence of a tertiary amine and catalytic amoimts of the combination of palladium acetate and triphenylphosphine. Concurrently, he reported the synthesis of benzamides from an aryl iodide, carbon monoxide, a primary amine, and a tertiary amine as base catalyzed by the same type of palladium complex. The related reactions of vinyl halides were also reported, and these reactions occurred with retention of the olefin geometry. ... 

In 1967 elimination of phenol from allyl phenyl ethers to form 1,3-diene in the presence of a palladium catalyst was reported briefly by Smutny. Later, Tsuji applied the Pd-catalyzed elimination reaction of terminal allylic compounds for the synthesis of terminal 1,3-dienes.Thus, elimination of acetic acid and phenol from allylic acetates and allyl phenyl ethers was carried out by refluxing the allylic compounds in dioxane or toluene in the presence of catalytic amounts of palladium acetate and PPha as a ligand for the palladium catalyst (Table 1). The allylic isomers were converted to the same products. No reaction takes place with allylic methyl ether, an allylic alcohol, or an allylic amine, which cannot easily form 7r-allylpalladium complexes by oxidative addition. 

Based on the above-mentioned stereochemistry of the allylation reactions, nucleophiles have been classified into Nu (overall retention group) and Nu (overall inversion group) by the following experiments with the cyclic exo- and ent/n-acetales 12 and 13[25], No Pd-catalyzed reaction takes place with the exo-allylic acetate 12, because attack of Pd(0) from the rear side to form Tr-allyl-palladium is sterically difficult. On the other hand, smooth 7r-allylpalladium complex formation should take place with the endo-sWyWc acetate 13. The Nu -type nucleophiles must attack the 7r-allylic ligand from the endo side 14, namely tram to the exo-oriented Pd, but this is difficult. On the other hand, the attack of the Nu -type nucleophiles is directed to the Pd. and subsequent reductive elimination affords the exo products 15. Thus the allylation reaction of 13 takes place with the Nu nucleophiles (PhZnCl, formate, indenide anion) and no reaction with Nu nucleophiles (malonate. secondary amines, LiP(S)Ph2, cyclopentadienide anion). 

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... 

---