Palladium synthesis

Deng, J., Wu, Y.M. and Chen, Q.Y. (2005) Cross-coupling reaction of iodo-1,2,3-triazoles catal3 ed by palladium. Synthesis, 2730-8. 

Cenini, S. Bettettini, E. Fedele, M. Tollari, S. (1996) Intramolecular amination catalyzed by ruthenium and palladium synthesis of 2-acyl indoles and 2-aryl quinolines by carbon-ylation of 2-nitrochalcones, J. Mol Catal A-Chem., Ill, 37-41. 

Li JJ, Xu XY, Jiang Z, Hao ZP, Hu C. Nanoporous silica-supported nanometric palladium Synthesis, characterization, and catalytic deep oxidation of benzene. Environ Sci Tech 2005 39 1319-1323. 

Y. Shi, K.E. Roth, S.D. Ramgren, S.A. Blum, Catalyzed catalysis using carbophiUc Lewis acidic gold and Lewis basic palladium synthesis of substituted butenolides and isocoumarins, J. Am. Chem. Soc. 131 (2009) 18022-18023. 

Palladium Compounds, Complexes, and Ligands Widely Used in Organic Synthesis... 

J. Tsuji. Organic Synthesis with Palladium Compounds, Springer. Berlin. 1980. 

The 5-oxohexanal 27 is prepared by the following three-step procedure (1) 1,2-addition of allylmagnesium bromide to an a, / -unsaturated aldehyde to give the 3-hydroxy-1,5-diene 25, (2) oxy-Cope rearrangement of 25 to give 26, and (3) palladium catalyzed oxidation to afford 27. The method was applied to the synthesis of A -2-octalone (28), which is difficult to prepare by the Robinson annulation[25]. 

In the prostaglandin synthesis shown, silyl enol ether 216, after transmetaJ-lation with Pd(II), undergoes tandem intramolecular and intermolecular alkene insertions to yield 217[205], It should be noted that a different mechanism (palladation of the alkene, rather than palladium enolate formation) has been proposed for this reaction, because the corresponding alkyl enol ethers, instead of the silyl ethers, undergo a similar cyclization[20I],... 

In the synthesis of morphine, bis-cyclization of the octahydroisoqtiinolinc precursor 171 by the intramolecular Heck reaction proceeds using palladium trifluoroacetate and 1,2,2,6,6-pentamethylpiperidine (PMP). The insertion of the diene system forms the rr-allylpalladium intermediate 172, which attacks the phenol intramolecularly to form the benzofuran ring (see Section 1.1.1.3). Based on this method, elegant total syntheses of (-)- and (+ )-dihydrocodei-none and (-)- and ( + )-morphine (173) have been achieved[141]. 

Ketones can be prepared by trapping (transmetallation) the acyl palladium intermediate 402 with organometallic reagents. The allylic chloride 400 is car-bonylated to give the mixed diallylic ketone 403 in the presence of allyltri-butylstannane (401) in moderate yields[256]. Alkenyl- and arylstannanes are also used for ketone synthesis from allylic chlorides[257,258]. Total syntheses of dendrolasin (404)f258] and manoalide[259] have been carried out employing this reaction. Similarly, formation of the ketone 406 takes place with the alkylzinc reagent 405[260],... 

I undertook the present task to give a birds-eye view of the broad field of palladium in organic synthesis. 1 have tried to accomplish this ttisk by citing many references these were selected from a much larger number which I have collected over the years. I tried to be as comprehensive as possible by selecting those references which reported original ideas and new reactions, or evident synthetic utility. Synthetic utility is clearly biased towards catalytic rather than stoichiometric reactions and this emphasis is apparent in the selection of the... 

The development of methods for aromatic substitution based on catalysis by transition metals, especially palladium, has led to several new methods for indole synthesis. One is based on an intramolecular Heck reaction in which an... 

The reaction is used for the chain extension of aldoses in the synthesis of new or unusual sugars In this case the starting material l arabinose is an abundant natural product and possesses the correct configurations at its three chirality centers for elaboration to the relatively rare l enantiomers of glucose and mannose After cyanohydrin formation the cyano groups are converted to aldehyde functions by hydrogenation m aqueous solution Under these conditions —C=N is reduced to —CH=NH and hydrolyzes rapidly to —CH=0 Use of a poisoned palladium on barium sulfate catalyst prevents further reduction to the alditols... 

More recently, a commercial process has been introduced for the manufacture of methyl isocyanate (MIC) which involves the dehydrogenation of /V-m ethyl form am i de [123-39-7] in the presence of palladium, platinum [7440-06-4], or mthenium [7440-18-8], at temperatures between 50—300°C (31). Aprotic solvents, such as ben2ene [71-43-2], xylenes, or toluene [108-88-3], may optionally be used. A variation of this synthesis employs stoichiometric amounts of palladium chloride [7647-10-1], PdCl2. 

Synthesis. The most common staiting materials for palladium complexes are PdCl2 [7647-10-1] and [PdClJ [14349-67-8]. Commercially available materials useful for laboratory-scale synthesis iuclude [Pd2(OOCCH2)J [3375-31-3] [PdCl2(NCCgH )] [14220-64-5] [Pd(acac)2] [14024-61-4] [PdCl2(cod)] [12107-56-1], and [Pd(P(CgH5)3)J [14221-01-3]. 

R. F. Heck, Palladium Keagents in Organic Synthesis, Academic Press, Inc., New York, 1985. 

Other useful references are R. E. Heck, Palladium Reagents in Organic Synthesis Academic Press, New York, 1985, and J. Tsuji, Organic Synthesis with Palladium Compounds, Sptinger-Vedag, New York, 1980. 

Polymerization by G—G Goupling. An aromatic carbon—carbon coupling reaction has been employed for the synthesis of rigid rod-like polyimides from imide-containing dibromo compounds and aromatic diboronic acids ia the presence of palladium catalyst, Pd[P(CgH )2]4 (79,80). 

A low temperature catalytic process has been reported (64). The process involves the divalent nickel- or zero-valent palladium-catalyzed self-condensation of halothiophenols in an alcohol solvent. The preferred halothiophenol is -bromothiophenol. The relatively poor solubiHty of PPS under the mild reaction conditions results in the synthesis of only low molecular weight PPS. An advantage afforded by the mild reaction conditions is that of making telecheHc PPS with functional groups that may not survive typical PPS polymerization conditions. 

In the synthesis of Win 57,273 the attachment of the group, a 2,6-dimethylpytidinyl group, involves formation of a carbon-carbon bond rather than a carbon-nitrogen bond. The method for the attachment of this group is a palladium mediated coupling reaction (77,78) of 4-tributylstarmyl-2,6-dimethylpyridine [122033-61 -8] with a 7-halo quinolone (26). 

Later, a completely different and more convenient synthesis of riboflavin and analogues was developed (34). It consists of the nitrosative cyclization of 6-(A/-D-ribityl-3,4-xyhdino)uracil (18), obtained from the condensation of A/-D-ribityl-3,4-xyhdine (11) and 6-chlorouracil (19), with excess sodium nitrite in acetic acid, or the cyclization of (18) with potassium nitrate in acetic in the presence of sulfuric acid, to give riboflavin-5-oxide (20) in high yield. Reduction with sodium dithionite gives (1). In another synthesis, 5-nitro-6-(A/-D-ribityl-3,4-xyhdino) uracil (21), prepared in situ from the condensation of 6-chloro-5-nitrouracil (22) with A/-D-ribityl-3,4-xyhdine (11), was hydrogenated over palladium on charcoal in acetic acid. The filtrate included 5-amino-6-(A/-D-ribityl-3,4-xyhdino)uracil (23) and was maintained at room temperature to precipitate (1) by autoxidation (35). These two pathways are suitable for the preparation of riboflavin analogues possessing several substituents (Fig. 4). 

Hydrogenation of Acetylenes. Complete hydrogenation of acetylenes to the corresponding alkanes, which maybe requited to remove acetylenic species from a mixture, or as a part of a multistep synthesis, may be accompHshed using <5 wt % palladium or platinum on alumina in a nonreactive solvent under very mild conditions, ie, <100°C, <1 MPa (10 atm). Platinum is preferred in those cases where it is desired to avoid isomeri2ation of the intermediate olefin. Silver on alumina also can be used in this appHcation as can unsupported platinum metal. 

Reduction of Acid Chlorides to Aldehydes. Palladium catalysis of acid chlorides to produce aldehydes is known as the Rosenmund reduction and is an indirect method used in the synthesis of aldehydes from organic acids. 

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