Palladium ethylenediamine

The reactivity of a series of closely related substances can either be enhanced or inhibited depending on the type and extent of interaction with double-helical DNA. This was shown in a kinetic study of the substitution of ethylenediamine (en) or A-, A- -dimethylethylcncdiamine (Me2en) by thiourea in the palladium(II) complexes [Pd(4,4,-R2bpy)(en)](PF6)2 (R = H or Me), [Pd(en)2](PF6)2, and [Pd(Me2en)2](PF6)2, in water and in the presence of calf thymus DNA.183... 

The removal of carbobenzyloxy (Cbz or Z) groups from amines or alcohols is of high interest in the fine chemicals, agricultural and pharmaceutical industry. Palladium on activated carbon is the catalyst of choice for these deprotection reactions. Nitrogen containing modifiers are known to influence the selectivity for certain deprotection reactions. In this paper we show the rate accelerating effect of certain N-containing modifiers on the deprotection of carbobenzyloxy protected amino acids in the presence of palladium on activated carbon catalysts. The experiments show that certain modifiers like pyridine and ethylenediamine increase the reaction rate and therefore shorten the reaction times compared to non-modified palladium catalysts. Triethylamine does not have an influence on the rate of deprotection. 

More hindered nitrogen bases were not effective modifiers, suggesting an interaction of the N-containing base with the palladium metal surface of the catalyst (8). Ethylenediamine forms a complex with palladium on carbon... 

Figure 3 demonstrates the influence of different modifiers on the reaction rate. Compared to the unmodified 5%Pd catalyst, the addition of 20 pi of pyridine or 20 pi of ethylenediamine increased the reaction rate from 1.5 to 2 mmol / (min gram) catalyst. Adding twice the amount of modifier (40 pi pyridine) does not increase the reaction rate any further. Obviously all the available surface palladium is already effectively modified. In contrast triethylamine does not exhibit any influence on the reaction rate. 

A commercially available 5% palladium on activated carbon catalyst from Degussa was used for the investigation. Commercially supplied N-(Carbo-benzyloxy)-L-phenylalanine (99%) was purchased from Aldrich. Modifiers such as pyridine, triethylamine, ethylenediamine and DABCO (Diazabicyclooctane) with a purity >99 % are also available commercially and were used as received. 

The self-assembly of di[4-(5-pyrimidyl)phenyl]dimethylsilane and -germane with (ethylenediamine)palladium dinitrate in an 1 2 ratio generated a new octahedral supramolecule containing group 14 elements <06ICC50>. 

Kibayashi and co-workers103 implemented the palladium-catalyzed cycloisomerization reaction in a stereoselective total synthesis of enantiomerically pure (+)-streptazolin. The cycloisomerization of enyne 172 to provide diene 173 was remarkably selective when performed in the presence of A,Ar -bis(benzylidene)ethylenediamine (BBEDA) as a ligand and water as a proton source (Scheme 44). 

Palladium was also effective in promoting the conversion of the indolyl-triflate shown in 4.22. to the tricyclic indolopyrazine system. The reaction, proceeding by the incorporation of a molecule of ethylenediamine, also proceeded in the absence of the palladium catalyst, but it was more sluggish and gave lower yields. Tetracyclic indolo[2,3-6]quinoxaline was also prepared in the same manner, using o-phenylenediamine as nucleophile.25... 

Table 1. Wave-numbers o (in the unit 1000 cm-1) and oscillator strengths P (in the unit 10—S) of spin-allowed (but Laporte-forbidden) transitions in nickel(II), copper(II) and palladium(II) complexes of water, ammonia, ethylenediamine (en), diethylenetriamine (den) and pyridine (py). Shoulders in parentheses...

Palladium-gold forms a continuous range of solid solutions (Section 2.6) and supported bimetallic particles are easily made. XAFS measurements confirmed that co-adsorption of [Au(en)2]3+ (en = ethylenediamine) and [Pd(NH3)4]2+ cations at natural pH onto silica gave small bimetallic particles (<5nm) after reduction at 623 K, irrespective of the Pd Au ratio.181 The same result was obtained by controlling the pH at 10 (Pd Au = 1), but at pH 7 (Pd Au = 1.3), reduction at 573K gave particles with a gold-rich... 

In a patent dealing with the selective hydrogenation of alkynols, use of palladium catalysts in combination with lower aliphatic amines such as butylamine, ethanolamine, and ethylenediamine, or in liquid ammonia was claimed to be more effective than use in the presence of higher amines, and superior to Lindlar catalyst in both activity and selectivity.43 Thus, linalool was obtained almost quantitatively by hydrogenation of 3,7-dimethyl-6-octen-l-yn-3-ol over Pd-CaC03 in the presence of butylamine (eq. 4.13). 

Alternative catalysts such as palladium-on-barium sulfate (poisoned by synthetic quinoline) (24), "P-2" nickel boride (with ethylenediamine) (25), and other nickel catalysts (19c) can be used in place of Lindlar catalyst. However, in our hands selective hydrogenation of triple bonds to Z olefins proceeds with the greatest stereoselectivity with Lindlar catalyst. Palladium-on-barium sulfate (in ethanol with quinoline) can give considerable over-reduction and isomerization to the E isomer (22a). Use of "P-2" nickel boride as the catalyst at room temperature usually gives a. 2% of the J5 isomer (e.g. 23). 

In contrast to Lindlar catalyst we have found that the hydrogenation of an alkyne over ethylenediamine-poisoned "P-2" nickel boride or quinoline-poisoned palladium-on-barium sulfate always gives a minor amount of the saturated hydrocarbon in addition to the olefin. The ratio of saturated hydrocarbon to olefin (about 0.01) also is nearly constant throughout the hydrogenation until the alkyne is consumed, and then it increases. Further reaction of the alkene on the catalyst surface before desorption would explain these results. 

Dichloro(ethylenediamine)palladium(II) is formed as yellow needles. (2,2 -Bipyridine)dichloropalladium(II) is produced as a light yellow microcrystalline solid that can be obtained as larger crystals by careful recrystallization from hot, dilute HC1 solutions. Both compounds are insoluble in cold water, but are moderately soluble in hot water. The compounds dissolve in 1 M sodium hydroxide with reaction. In general the compounds are not soluble in organic solvents however, both complexes can be dissolved in dimethyl sulfoxide and A>Y-di met hy If or mami de. 

---