Diamines, chelating

In another attempt to achieve efficient coordination, we have used a strongly chelating diamine (4.43) in the Mannich reaction with 4.39 (Scheme 4.12). The reaction was performed in aqueous ethanol, producing 4.44-2HC1 in 64% yield. 

Prepa.ra.tion, The preparation of amorphous high (99%) 1,2-polybutadiene was first reported iu 1981 (27). The use of a heterocycHc chelating diamine such as dipiperidine ethane iu the polymerization gave an amorphous elastomeric polymer of 99.9% 1,2 units and a glass-transition temperature of +5°C. In a previous description (53,54) of the use of a chelating diamine such as A/A/N(N -tetramethylethylene diamine, an 80% 1,2-polybutadiene with a glass-transition temperature of —30°C was produced. 

Several reports iu the Hterature describe the preparation and characterization of low, medium, and high vinyl polybutadienes (55—69). Each of these references used polar modifiers including chelating diamines, oxygenated ether compounds, acetals, ketals, and compounds of similar stmctures (56—64). 

It has been found that a number of bidentate ligands greatly expand the scope of copper catalysis. Copper(I) iodide used in conjunction with a chelating diamine is a good catalyst for amidation of aryl bromides. Of several diamines that were examined, rra s-yV,yV -dimethylcyclohexane-l,2-diamine was among the best. These conditions are applicable to aryl bromides and iodides with either ERG or EWG substituents, as well as to relatively hindered halides. The nucleophiles that are reactive under these conditions include acyclic and cyclic amides.149... 

Two chelating diamine ligands. One of the 2 hfac groups forms long Cu—O bonds in axial positions... 

A study was carried out applying Li and C NMR spectroscopies, on the behavior of Li-enriched BuLi and PhLi (RLi) in toluene solution, in the presence of chelating diamines 141-143 and (—)sparteine (24), denoted by L. Dimeric complexes 2RLi-2L... 

The ligand chosen to complex n-BuLi affects not only the configuration of the carban-ion but also the regioselectivity of the addition to a,/S-unsaturated ketones (Scheme 65). Depending on the chelating diamine, the ratio of 1,2- V5. 1,4-addition can range from 95 5 to 6 94. With (—)-sparteine, 1,4-addition to enones predominates when TMSCl is present. Diastereoselectivity in the formation of the two new stereocenters is >99 1, and enantioselectivity is >96%. Subsequent alkylation, in one pot, is also possible. ... 

While nitroprusside itself is substitution inert, the reduction product, [Fe(CN)5(NO)] , rapidly loses the trans cyanide (see above) and [Fe(CN)4(NO)] is substitution labile via a dissociative pathway and is rapidly substituted by chelating diamines to give products such as... 

Experiments with 90 percent enrichment in the 1 or 2 position of 1,3 butadiene confirm earlier work that the live end is predominantly a 1,4 unit with a trans/cis ratio of /l The Li is bound to the Q( carbon of the 1,4 butadiene unit in what appears to be a highly localized 0 bond However, the presence of partial ionic character in the bond cannot be ruled out There is no evidence of Li being gf bonded to the carbon When a chelating diamine such as dipiperidyl ethane is added to the live cement, a drastic change takes place in the spectrum which suggests complete conversion to a delocalized ionic bonding. 

The unique feature about anionic polymerization of diene to produce homopolymer was that the microstructure of the homopolymer could be altered and changed at will to produce unique physical and chemical properties. These microstructural changes can be introduced before, after or during the polymerization. For example, chelating diamines, such as tetramethyl ethylene and diamine (TMEDA) (18), with the alkyl-lithium catalyst have been used to produce polymer with 80 1,2 addition products, while the use of dipiperidine ethane (DPE),with same catalyst has produced polybutadiene with 100 1,2 addition product. 

Fig. 20. Proposed mechanism for the oxidation of chelating diamine ligands bound to [Fen(CN)4 2-, with formation of different intermediates involving Fe11, Feln species, and final formation of the [Fen(CN)4(diimine)]2 complexes.

For ease of systematization, we will regard all chelate diamine "ligands with the two nitrogen donors separated by —(CH2)2— as related to ethylenediamine (en). These generally form five-membered chelate rings and the atoms will be numbered consecutively N(l)—C(2)—C(3)—N(4). 

This lithiation reaction is carried out in the presence of the chelating diamine TMEDA 19 because, in hydrocarbon solvents, alkyllithiums are thought to react as aggregates such as 20 or mixtures of aggregates and dissociated species.7 Donor solvents like THF or even better diamines like 19 effectively break down alkyllithium aggregates, forming monomers and dimers 21 in solution, and thereby significantly increase their basicity and reactivity towards deprotonation.7 The use of MTBE as the solvent avoids the competitive attack of n-butyllithium on THF at the required reaction temperature of < 5 °C.7c... 

Eberhardt and co-workers (12, 13) found that lithium alkyls are active toward the telomerization of ethylene and benzene when a tert-amine or chelating diamine, such as sparteine or N.N.JV. Af -tetramethylenethy-lenediamine (TMEDA), is used [Eqs. (1)—(3)]. 

All of the studies published to date fail to identify the active catalyst species present in the RLi-TMEDA polymerization of ethylene. The kinetics data of both Hay and Shud and their co-workers fall short in this respect. A more fundamental approach is needed. It may be appropriate at this time to study the 13C- and 7Li-NMR of alkyllithium compounds in the presence of various chelating diamines and polar modifiers such as THF and dimethyl ether. 

Osmium tetroxide on treatment with the chelating diamine L2 (L2 = [R,R]-trans-1,2 bis[N-pyrrolidino]cyclohexane) gives 0s04L2. What is the electron count in this complex, and does this have any relevance to the ADH mechanism ... 

The lithium derivative of the chiral chelating diamine (3 )-2-(l-pyrrolidinylmethyl)-pyrrolidine (6) has been used extensively in stereoselective synthesis, i.e. in the deprotonation of ketones and rearrangement of epoxides to homoallylic alcohols. The lithium amide has been crystallized from toluene solution, and X-ray analysis revealed that it forms a ladder-type tetramer with the two pyrrolidine nitrogens solvating the two lithiums at the end of the ladder38, (Li-6)4. 

The reactions of iridium olefin complexes are not restricted to reactions with phosphines. Amines have also employed in bridge-splitting and substitution reactions with [Ir(COD)Cl]2, especially chelating diamines. The reactions proceed to yield [Ir(COD)N-N]2 compounds. A fertile chemical area involves the irw(pyrazolyl)borate (see Tris(pyrazolyl)borates) family of compounds with the monoethylene and bisethylene complexes serving as reactive entries in this field. ... 

Catalyst systems obtained in situ from rare-earth metal trisamides Ln N-(SiMc3)2 3 and various chelating diamines (Fig. 17) have shown good activity in the cyclization of aminoalkenes (Schemes 3 and 4) [123,125-127]. The more challenging cyclization of the chiral aminoalkene 26 can be accomplished with... 

Fig. 17 Chelating diamines used as ligands for nonmetallocene hydroamination catalysts...

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