Diamines, as ligands

The addition to a, -unsaturated esters is usually difficult. However, under appropriate conditions, the 1,4-addition of diorganozincs to enoates is possiblc As mentioned above, Michael-addition reactions can also be catalyzed by Ni(II) salts . The 1,4-addition of functionalized organozinc iodides to enones in the presence of Ni(acac)2, a diamine as ligand and TMSCl provides, after hydrolysis, the Michael adducts in satisfactory yields . 

Further, an interesting feature of these diamines as ligands for the copper(II) ion has been recognized (24). As illustrated in Figure 5, there are two geometrical ways of coordination cis and trans. In the cis form, where the primary and secondary amino groups take positions cis to one another, the two apical position on the copper(II) ion are considered to be blocked from the coordination because of the presence of the diamine skeleton,... 

Prior to our work, there had been few reports of platinum complexes bearing monoprotonated (or monoalkylated) diamines as ligands. To our knowledge, only three complexes having this structure have been characterized. Terzis ( ) prepared and determined the crystal structure of trichloro(9-methyladeninium)... 

Modified diamines as ligands, including monophosphonamides (e.g., 48 ) and carboxamides (e.g., 49 ), have been scrutinized. In the use of 49 for forming complexes with the... 

Another system where C—N bond formation was observed is in the synthesis of indazoles 112. The synthesis of heterocycles 112 from (Z)-2-bromoacetophenone tosylhydrazones 111 involves a catalytic system composed of a diamine as ligand, such as A, AP-dimethylethane-1,2-diamine and KjCOj at rt (Eq. 10.38) [83]. The mechanism proposed is the intramolecular ET from the nucleophilic center to the pendant aryl bromide, fragmentation, and radical-radical coupling (seeEq. 10.31) ... 

In 2011, a related methodology using chiral diamine as ligand was... 

Li L, Wu J, Wang F, Liao J, Zhang H, Lian C, Zhu J, Deng J. Asyimnetric transfer hydrogenation of ketones and imines with novel water-soluble chiral diamine as ligand in neat water. Green Chem. 2007 9 23-25. 

Mukaiyama, T., and Asami, A. Chiral Pyrrolidine Diamines as Efficient Ligands in Asymmetric Synthesis. 127,133-167(1985). 

Chiral salen ligands are diimines of salicylaldehydes with chiral diamines, usually cyclohexane-1,2-diamine (salen Hgands 1) or 1,2-diphenylethylene-diamine (salen ligands 2). The most widely used salen ligand in homogeneous catalysis is probably Jacobsen s ligand (la. Fig. 2), which is commercially available and hence has been used as reference to compare the results of im-... 

Chiral amines and diamines are readily available substrates for the synthesis of ligands for transition metal-catalysed reactions since they can easily be transformed into chiral ureas and thioureas. Therefore, several groups have prepared chiral symmetrical ureas and thioureas, dissymmetrical ureas and thioureas, amino-urea and thiourea derivatives. Finally polyureas and non-soluble polythioureas were also prepared and tested as ligands for asymmetric catalysis. 

The reaction was first tested with these substances as ligands but the organic molecule, in the absence of any added metal ion, proved to be the most enantioselective catalyst (library 1 19% ee vs. less than 13% ee for the best metal catalyst). The effects of selective variations of the amino acid nature and of the salicylidene moiety on the diamine structure were investigated for urea and thiourea derivatives via HTS (library 2 48 urea compounds and... 

In 1997 the first asymmetric aza-Claisen rearrangement was reported by Overman et al. [55], which made use of diamines as bidentate ligands for Pd(II), allowing for moderate enantioselectivities. In the same year, Hollis and Overman described the application of the planar chiral ferrocenyl palladacycle 38 as a catalyst for the enantioselective aza-Claisen rearrangement of benzimidates 39 (Fig. 19) [56]. A related ferrocenyl imine palladacycle provided slightly inferior results, while a benzylamine palladacycle lacking the element of planar chirality was not able to provide any enantioselectivity [57]. 

In acid media, the complexes undergo rapid hydrolysis to yield free diamines, as shown for [Tc02(en)2] + [43]. The stability of the complexes is between that of O-coordinated and S-coordinated complexes, as shown in the reaction sequence of Tc(V) gluconate with pyridine, ethylenediamine or o-phenylenediamine to give the cationic N-coordinated species these, in turn, are able to exchange the nitrogen ligands by dithiols, such as DMSA [40]. 

As with hydrogenation, hydrogen transfer of imines is a poorly developed field.126-130 However, recent arene-Ru11 systems bearing chiral 1,2-diamine co-ligands have been found to be excellent catalysts for asymmetric reduction of imines with formic acid as donor.31,131-134... 

RuCl2(PPh3)3 has been shown to catalyze the reduction of several aldehydes, but does not have widespread scope. This catalyst is not chemoselective and, in the presence of alkenes, would favor olefin reduction over that of the aldehyde. Noyori and coworkers showed that chemoselectivity is easily introduced by the addition of ethylene-diamine as a ligand (Scheme 15.6) [29, 30]. This system requires the presence of co-catalytic KOH/i-PrOH as an activator. 

Diamines and Diimines as Ligands C. Other Group-Transfer Reactions... 

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