Reduction of 1,2-Diketimines

By an alternative approach, the enantioselective reduction of 1,2-diketimines was achieved by using hydride reagents in the presence of stoichiometric amounts or an excess of enantiopure carboxylic acids. An... 

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... 

In contrast to 53, reduction of 3,5- Pr2-Ar FeCl 2 in the presence of benzene afforded the orange half-sandwich complex 54. The iron is coordinated to the ipso carbon of the terphenyl ligand and a benzene in an ti fashion. The C( 1 )-Fe-centroid is strictly linear and the Fe(l)-centroid distance of 1.6427(13)A is similar to the Fe-centroid distance of 1.6245(8) A in the related P-diketiminate Fe(I) complex [ (C6H3-2,6-Pr2)NC(Me) 2CH]Fe(Ti -C6H6) [94], but is shorter than the 1.733(2) and 1.763(2) A in Ar FeFeAr (42). Magnetic studies showed that the Fe(I) center adopts a high-spin configuration with three unpaired electrons. 

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