Zinc -diamine

The redox reaction between diphenylbenzidine and thiosulfate is of first order with respect to thiosulfate, diphenylbenzidine, and hydrogen ions.301 Zinc-diamine-catalysed reduction of various ketones with polymethylhydrosiloxane in protic conditions show moderate enantioselectivities. Probable mechanisms are proposed.302 Reduction of non-activated aryl and alkyl halides by a neutral ground-state organic molecule (13) afforded the corresponding indolines in excellent yields. A tentative mechanism has been suggested (Scheme 13).303... 

Diamine curatives were the first cross-linking agents for fluorocarbon mbbers. They are corrosive to mild steel molds and have been replaced in many appHcations by the bisphenol or other more recent cure systems. Nevertheless, some diamines are stiU used for food-contact appHcations of fluorocarbon mbbers and in zinc-free cures of halobutyl mbbers for pharmaceutical stoppers. Methylene dianiline and triethylene tetramine are cross-linking agents for ethylene—acryflc elastomers. 

Some instances of incomplete debromination of 5,6-dibromo compounds may be due to the presence of 5j5,6a-isomer of wrong stereochemistry for anti-coplanar elimination. The higher temperature afforded by replacing acetone with refluxing cyclohexanone has proved advantageous in some cases. There is evidence that both the zinc and lithium aluminum hydride reductions of vicinal dihalides also proceed faster with diaxial isomers (ref. 266, cf. ref. 215, p. 136, ref. 265). The chromous reduction of vicinal dihalides appears to involve free radical intermediates produced by one electron transfer, and is not stereospecific but favors tra 5-elimination in the case of vic-di-bromides. Chromous ion complexed with ethylene diamine is more reactive than the uncomplexed ion in reduction of -substituted halides and epoxides to olefins. ... 

Treatment of the heterocycle, 38 (obtained from ethylene-diamine and carbon disulfide), with nitrous acid affords the N-nitroso compound, 39. Reduction with zinc leads to the corre-... 

The alternative product from pyridine-3,4-diamine and ethyl acetoacetate, compound 12, is obtained by the base-catalyzed cyclization of the ester 11, which is formed from the diamine and ethyl acetoacetate in the presence of zinc(II) chloride.298... 

The couphng of N-substituted benzaldimines, mediated by the zinc-copper couple in the presence of (+)-camphorsulfonic acid (CSA) in DMF, was investigated. The best results were obtained for the imine 22, and the optimal balance of yield, diastereoselectivity and enantioselectivity for the diamine 23 was obtained using 3equiv of (+)-CSA [17] (Schemes). How-... 

An approach to the preparation of asymmetrically 1,2-disubstituted 1,2-diamines has been reported the zinc-copper-promoted reductive coupling of two different N-(4-substituted)phenyl aromatic imines, one bearing a 4-methoxy and the other a 4-chloro substituent, in the presence of either boron trifluoride or methyltrichlorosilane, gave a mixture of the three possible 1,2-diamines, where the mixed one predominated [31 ]. Low degrees of asymmetric induction were observed using 1-phenylethylamine, phenylglycinol and its 0-methyl ether, and several a-amino acid esters as the chiral auxiharies meanwhile the homocoupling process was not avoided (M.Shimizu, personal communication). 

A series of zinc diphosphonate complexes were synthesized in the presence of diamines of varying chain length. 1-hydroxyethylidenediphosphonate bridges the metal ions with the proto-nated diamine (ethyl-, butyl-, pentyl-, or hexylenediamine) filling in channels or residing between chains. All four structures are different with one-, two-, and three-dimensional networks formed. The coordination number (4-6) and geometry also varies.418... 

Polymeric network structures of zinc and selenium with A.A -ethylenediamine have been formed and structurally characterized. The tetrahedral zinc centers are Se3N coordinated with the diamine bridging to give two-dimensional slabs 586... 

TMEDA can also participate in the formation of multinuclear zinc telluride complexes with Znio, Zni4, and Zni6 complexes structurally characterized. A comparison was carried out by Pfistner et al. replacing the diamine with a diphosphorus ligand, bis(diphenylphosphino)methane,... 

Heterocyclic nitrogen donors and their adducts with zinc chloride have been studied.623,624 A large number of other ligand systems have also been characterized, for example, zinc halide adducts of 2,2-dimethylpropane-1,3-diamine and hexamethylphosphoramide have been studied.625,626 The formation of mixed ligand complexes with chloride and substituted pyridines has been studied.627 The zinc tris(pyridyl) chloride anion has also been structurally characterized.628 Manganese(II) ions have been used to probe the stereochemistry in reactions of zinc halides with pyrazine.629... 

Small-ring cyclic diamines have already been discussed in Chapter 1.20. The azamacrocycles offer the possibility for functionalization at the nitrogen donor groups and many examples will be presented from triazamacrocycles up to much larger polyaza macrocycles that will bind more than one zinc ion. Particular mention must be made of the large contribution of Kimura and co-workers to this area. 

The ligand 6,13-dimethyl-l,4,8,ll-tetra-azacyclotetradecane-6,13-diamine coordinates as a hexadentate ligand to zinc in neutral aqueous solution. Potentiometric titrations were used to determine the stability constant for formation. The pXa values were determined for five of the six possible protonation steps of the hexamine (2.9, 5.5, 6.3, 9.9 and 11.0).697 Studies of the syn and anti isomers of 6,13-dimethyl-1,4,8, ll-tetraazacyclotetradecane-6,13-diamine reveal that they offer different shapes for metal binding, which is reflected in the stability constants for 1 1 zinc ligand ratio complexes. The selectivity of binding to the zinc ion compared to the cadmium(II) ion by both isomers is significant.698... 

The zinc iodide complex of a 15-membered diamine diimine macrocycle has been structurally... 

Recently, novel bifunctionalized zinc catalysts have been developed (compounds (N) and (P), Scheme 55). They have both Lewis-acid and Lewis-base centers in their complexes, and show remarkable catalytic activity in direct aldol reactions.233-236 A Zn11 chiral diamine complex effectively catalyzes Mannich-type reactions of acylhydrazones in aqueous media to afford the corresponding adducts in high yields and selectivities (Scheme 56).237 This is the first example of catalytic asymmetric Mannich-type reactions in aqueous media, and it is remarkable that this chiral Zn11 complex is stable in aqueous media. 

Kim and Varma have described the preparation of a range of cyclic ureas from diamines and urea [366]. In the example highlighted in Scheme 6.203, ethylenedi-amine and urea were condensed in the presence of 7.3 mol% of zinc(II) oxide in N,N-dimethylformamide as solvent at 120 °C to furnish imidazolidin-2-one in 95% isolated yield. Key to the success of this method is that the reaction needs to be performed under reduced pressure in order to remove the ammonia formed from the reaction mixture. This method was extended to a variety of diamines and amino alcohols [366]. 

Butyl, and the halogenated butyls, can be cured by sulphur, dioxime and resin cure systems. In addition, the halogenated types can be crosslinked with zinc oxide, and diamines. Peroxides cannot be used because they tend to depolymerise the polyisobutylene. 

Interesting results were reported with dithiocarbamates derived from diamines. Thus, a series of dinuclear zinc(II), cobalt(II), and nickel(II) dithiocarbamate ditopic macrocyclic receptors containing various spacer groups of different sizes has been reported.412,413,414 Spectroscopic investigations and... 

Diaminodiphenyl derivatives can be obtained from appropriately substituted nitrobenzenes by a rather dated process of alkaline reduction with zinc powder/ sodium hydroxide solution, which affords hydrazobenzene. A more recent method uses a catalytic reduction process with hydrogen and specifically deactivated catalysts of precious metals. Subsequent acid-catalyzed rearrangement with hydrochloric acid yields the hydrochloride of the target diamine ... 

Tri-ethylene diamine zinc hydroxide [Zn(en)3)(OH)2 Zincoxen Questionable solvating power, stable only at low temperatures, slight oxidative degradation, colourless... 

The equilibrium potentials of saturated zinc amalgam were determined [94] as a function of concentration of free ethylene-diamine in the solutions of pH 9.5, 10.5, and 11.5. The stability constants of complexes with different compositions, which were formed, have been estimated. 

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