Diimine 3-Diketonates

C-H insertion also occurs in the reactions with acetone and acetophenone, presumably through the rearrangement of transient OH-substituted phosphi-ranes [87]. C-C insertions occur for diketones to give 45 and have been postulated to occur via initial 1,2-addition to the conjugated enol 44 [87]. Diimines 46 also undergo C-C insertions [88]. Based on a theoretical evaluation, the products 47 are considered to result from a 2,3-sigmatropic rearrangement of initial formed P,N-ylids. 

Diketimines can be prepared by condensation of 1,2-diketones with 2 equiv of an amine, or 1 equiv of a 1,2-diamine, by azeotropic removal of water. Either a chiral diketone or a chiral amine/diamine can be used in order to obtain a chiral diimine. In both cases, the use of 1,2-diamines is expected to provide better stereocontrol, because of the rigidity of the derived cyclic diimines. For example, the reaction of camphor 1,2-diketone 275 and racemic 1,2-diphenylethylenediamine (d,l)-26 gave the diimine 276 as a mixture of two diastereomers (Scheme 45) [138]. Reduction of 276 with sodium borohydride followed by hydrogenolysis of the N substituents afforded the camphordiamine, which was isolated as the dihydrochloride... 

The observed pattern of C—C and C—N distances indicates delocalization of n-electrons within the six-membered P-diiminate rings. Open-chain tetraaza ligand complexes [AuL j, in which condensation of only one P-diketonate has occurred. 

Several combinatorial approaches to the discovery of transition metal based catalysts for olefin polymerization have been described. In one study Brookhart-type polymer-bound Ni- and Pd-(l,2-diimine) complexes were prepared and used in ethylene polymerization (Scheme 3).60,61 A resin-bound diketone was condensed with 48 commercially available aminoarenes having different steric properties. The library was then split into 48 nickel and 48 palladium complexes by reaction with [NiBr2(dme)] and [PdClMe(COD)], respectively, all 96 pre-catalysts being spatially addressable. 

The nucleophilic attack of organometallic species occurs with cleavage of the N—S bond and eventual formation of an a-diketone. This reaction has been shown to proceed through an unsym-metrical diimine (17) (Scheme 2) <90JHC1861>. The 4-unsubstituted series (18) can be functionalized in this way. The diimine product of ring opening (19) can add a nucleophile at carbon (20) and then be recyclized to a 3,4-disubstituted 1,2,5-thiadiazole (21) (Scheme 3) <86H1131>. 

Reactions of germylenes with 1,3-dienes, vinyl ketones, ot-diketones, vinyl imines, and a-diimines gave corresponding [4 - - 1] cycloadducts (Scheme 14.55). ... 

Diimines of a-diketones—reaction of aromatic aldimines with sodium cyanide in DMSO at 20°C (72 hr) [57]. 

Several series of macrocyclic p-diimine complexes have been shown to undergo reactions similar to those of the p-diketonates. Reversible protonation of the complexes (27) (equation 15) has been... 

Schiff bases having two nitrogen atoms as donors may be derived either from condensation of dialdehydes and diketones with two molecules of an amine, or from reaction of diamines with aldehydes or ketones. In Section 20.1.2.1, it has been pointed out that coordination through the N atom may occur only under particular circumstances. However, in the case of diimines the formation of chelate rings stabilizes the metal-nitrogen bond. Thus, they can form both mono-41 and bis-chelate42 complexes. 

Simple a-diimines are hydrolytically unstable, but can be stabilized as metal complexes by virtue of the formation of stable five-membered chelate rings.68 69 a-Diketones and glyoxal undergo metal template reactions with amines to yield complexes of multidentate ligands such as (34),70 (35)71 and (36).72>73 In the last case, the metal exerts its stabilizing influence on the a-diimine partner in an equilibrium process (Scheme 5). The same phenomenon occurs with amino alcohols74 75 in addition to amino thiols. The thiolate complexes (37) can be converted to macrocyclic complexes by alkylation in a kinetic template reaction (Scheme 5).76 77... 

Aza-analogues of oxygen compounds frequently show related reactivity patterns, and this is certainly seen in a comparison of the chemistry of imines and carbonyl compounds. For example, 1,3-diimines are readily deprotonated to yield the 1,3-diketonate analogues. The most frequent consequence of this is that reactions which are expected to yield 1,3-diimine complexes often lead to those of the deprotonated species. This is seen in the formation of the gold(m) complex of a deprotonated macrocycle in the reaction of 1,2-diaminoethane with 2,4-pentanedione in the presence of Na[AuCl4] (Fig. 5-4). The exact sequence of events in this reaction is not known, but note that the product is a square-planar gold(in) complex of the doubly-deprotonated macrocycle, rather than a gold(i) species ... 

The oxazaborolidine-catalyzed reduction of 1,2-diketones (Equation (258)),1116-1120 1,2-keto-imines (Equation (259)),1121-1123 and 1,2-diimines (Equation (260))1124 provided optically active 1,2-diols, amino alcohols, and 1,2-diamines with both high enantiomeric and diastereomeric excess. The method can be also effective for (3- and y-analogs. 

With complete exclusion of air, fra i -[FeCl2(H20)4] reacts with acetylacetone to form hydrated bis(2,4-pentanedionato)iron(II). The complex is coordinatively unsaturated and forms an interesting tetrameric structure [Fe4(acac)g] in which two asymmetric triply oxygen bridged dimers (32) are linked by rather long Fe-C bonds (2.785 A, 33). [Fe(acac)2] forms simple hexacoordinate adducts in reaction with a variety of bases, for example, heterocyclic diimines snch as bipyridines. Complexes formed by iron(II) with other /3-diketonates are polymeric and highly air sensitive. Iron(III), however, forms a series of stable highly colored... 

When a metal ion such as nickel (II) is absent, thiazoles and mercaptals are formed. Such reactions have been carried out in which the diketone was biacetyl, 2,3-pentanedione, 2,3-octanedione, l-phenyl-l,2-propane-dione, and 1,2-cyclohexanedione (51). In like manner, the tris complexes of W,W -dimethyl-2,3-butane diimine with iron(II), cobalt(II), and nickel(II) may be prepared from methylamine and biacetyl when the appropriate metal ion (27j 28j 41) is present. Replacing methylamine with hydroxylamine causes the formation of a-dioximes (13). 

Monoximes of a-diketones are reduced to o -aminoketones through an intermediate enaminol [88] dioximes of a-diketones are reduced to the diamines through diimines and endiamines. 

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