Palladium amination

Table 4 Palladium-Nitrogen Bond Lengths in Palladium Amine...

The 0.5 wt.% Pd/H-Mordenite catalyst was prepared by impregnating the commercial H-form mordenite material with a palladium amine complex solution [Pd(NH3)4]Cl2. Before the reaction, catalysts were reduced in the reactor at 400 °C under a hydrogen steam. Coke was liberated from a coked catalyst sample by dissolving the catalyst in a 40 % hydrofluoric acid solution. Finally, the coke sample was obtained by percolation, washed with deionized water and then dried. 

Many reactions of amines with palladium- and platinum-olefin complexes have been reported. Akermark showed that nucleophiles add to palladium-olefin complexes to generate aminoalkyl complexes, as shown by the example in Equation 11.26. In this case, reactions of a bis-olefin dichloropalladium complex with amines occurs by splitting of the chloro-bridged dimer by the first equivalent of amine to give a neutral olefin-ligated palladium-amine complex that undergoes attack of the coordinated alkene by a second equivalent of amine. The stereochemistry of the amination is cleanly trans. Akermark and Zetterberg isolated and characterized by C NMR spectroscopy the a-alkyl complexes formed by the amination of both cis- and frans-2-butene, and the stereochemistry of the product alkyl complexes results from external attack by amines, as shown in Scheme 11.5. 

Thus investigations involving palladium amines are ongoing and varied. 

These considerations are illustrated by an ad initio study of cationic palladium amine complexes. Experimentally, it is found that methylpalladium complexes of chelating terdentate nitrogen ligands insert CO readily. Calculations of the model reaction [PdMe(NH3)3] + CO [Pd(COMe)(NH3)3] showed that a purely five-coordinate pathway (with five ligands firmly coordinated to palladium) could be ruled out. Similarly, a purely dissociative route in which an NH3 ligand dissociates completely was high in energy. The most favorable route was found to be a hydrid pathway in which a five-coordinate intermediate is a transition state, first to partial NH3 dissociation. In the subsequent... 

Chelating agents may manifest their antiviral activity by metal sequestration and, as with bacteria and parasites, the natural differences between the host and invading cells may be exploited. Chelating agents with antiviral activity include the thiosemicarbazones, 1,10-phenanthrolines and phosphonoacetates. The latter compounds may act by zinc chelation. Metal complexes with antiviral action are platinum and palladium amines, as well as the antibacterial silver and mercury species. 

NMR signals of the amino acid ligand that are induced by the ring current of the diamine ligand" ". From the temperature dependence of the stability constants of a number of ternary palladium complexes involving dipeptides and aromatic amines, the arene - arene interaction enthalpies and entropies have been determined" ". It turned out that the interaction is generally enthalpy-driven and counteracted by entropy. Yamauchi et al. hold a charge transfer interaction responsible for this effect. 

The addition of N-bromosuccinimide (1.1equiv) to a dichlo-romethane solution containing the alkene (1 equiv) and cyana-mide (4 equiv). The solution was maintained at room temperature (3 days) and then washed with water, dried, and concentrated in vacuo. Treatment of the bromocyanamide [intermediate] with 1% palladium on charcoal in methanol (1h) led to reduction of the for-madine. Addition of base to the reaction mixture (50% aqueous KOH, reflux 6h) followed by extraction with ether gave monoamine. (Yield is 48-64% final amine from alkenes analogous to safrole)... 

Single-bond cleavage with molecular hydrogen is termed hydrogenolysis. Palladium is the best catalyst for this purpose, platinum is not useful. Desulfurizations are most efficiently per-formed with Raney nickel (with or without hydrogen G.R. Pettit, 1962 A or with alkali metals in liquid ammonia or amines. The scheme below summarizes some classes of compounds most susceptible to hydrogenolysis. 

Allylic acetoxy groups can be substituted by amines in the presence of Pd(0) catalysts. At substituted cyclohexene derivatives the diastereoselectivity depends largely on the structure of the palladium catalyst. Polymer-bound palladium often leads to amination at the same face as the aoetoxy leaving group with regioselective attack at the sterically less hindered site of the intermediate ri -allyl complex (B.M. Trost, 1978). 

B) palladium(0)-catalyzed direct amination of the O-acetylated allylic alcohol. 

The allyl bromides formed by method (A) contain 25% of the undesired (Z)-isomer. The selectivity of the palladium-catalyzed amination can be steered by the application of polymer-bound systems (see section 2.6.3 B. M. Trost, 1978),... 

Addition of several organomercury compounds (methyl, aryl, and benzyl) to conjugated dienes in the presence of Pd(II) salts generates the ir-allylpalladium complex 422, which is subjected to further transformations. A secondary amine reacts to give the tertiary allylic amine 423 in a modest yield along with diene 424 and reduced product 425[382,383]. Even the unconjugated diene 426 is converted into the 7r-allyllic palladium complex 427 by the reaction of PhHgCI via the elimination and reverse readdition of H—Pd—Cl[383]. 

In the reaction of aryl and alkenyl halides with 1,3-pentadiene (248), amine and alcohol capture the 7r-allylpalladium intermediate to form 249. In the reactions of o-iodoaniline (250) and o-iodobenzyl alcohol (253) with 1,3-dienes, the amine and benzyl alcohol capture the Tr-allylpalladium intermediates 251 and 254 to give 252 and 255[173-175]. The reaction of o-iodoaniline (250) with 1,4-pen tadiene (256) affords the cyclized product 260 via arylpalladiuni formation, addition to the diene 256 to form 257. palladium migration (elimination of Pd—H and readdition to give 258) to form the Tr-allylpalladium 259, and intramolecular displacement of Tr-allylpalladium with the amine to form 260[176], o-Iodophenol reacts similarly. 

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). 

Another protecting group of amines is 1-isopropylallyloxycarbonyl, which can be deprotected by decarboxylation and a /3-elimination reaction of the (tt-l-isopropylallyl)palladium intermediate under neutral conditions, generating CO2 and 4-methyl-1,3-pentadiene. The method can be applied to the amino acid 674 and peptides without racemization[437]. 

Nitro groups are readily reduced to primary amines by a variety of methods Cat alytic hydrogenation over platinum palladium or nickel is often used as is reduction by iron or tin m hydrochloric acid The ease with which nitro groups are reduced is especially useful m the preparation of arylamines where the sequence ArH ArN02 ArNH2 IS the standard route to these compounds... 

Chloro(tris[2-(dimethylamino)ethyl]amine) palladium(II) [66632-97-1]... 

Trichloroacetic acid K = 0.2159) is as strong an acid as hydrochloric acid. Esters and amides are readily formed. Trichloroacetic acid undergoes decarboxylation when heated with caustic or amines to yield chloroform. The decomposition of trichloroacetic acid in acetone with a variety of aUphatic and aromatic amines has been studied (37). As with dichloroacetic acid, trichloroacetic acid can be converted to chloroacetic acid by the action of hydrogen and palladium on carbon (17). 

Water hydroly2es pure diketene only slowly to give acetoacetic acid [541-50-4] which quickly decomposes to acetone and carbon dioxide, but increasing the pH or adding catalysts (amines, palladium compounds) increases the rate of hydrolysis. The solvolysis of diketene in ammonia results in aceto acetamide [5977-14-0] if used in stoichiometric amounts (99), and P-arninocrotonarnide [15846-25-0] if used in excess (100). 

Coordination Compounds. Palladium forms numerous complexes with ammonia and with simple amines. Examples ate [Pd(NH2)4] ... 

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