Meso-diamines

Imines can be stereoselectively hy-drodimerized to 1,2-diamines with rac/ meso rahos of 0.9 to 1.1 similar to the cathodic coupling of carbonyl compounds to pinacols in an acidic medium [304]. With 4,6-dimethylpyrimid-2-one only the meso-diamine was obtained [305]. Electroreduction of diimines prepared from... 

In the examination of other ititrogen-based ligands with this catalyst system, it was observed that achiral and meso diamines had a marked impact on catalyst enantioselectivities. The simple diamines, TMEDA and A,A,A, A -tetraethylethylene diamine were found to exhibit the opposite enantiofacial selectivity (Table 5). While TMEDA formed a catalyst that gave the (5 )-enantiomer of the product in 64% enantioselectivity (0°C), catalyst based on N,N,N, N -tetraethylethylene diamine generated the (/ )-enantiomer in up to 72% ee. 

The impact of achiral ligands on the TOP of the catalyst in this system was then examined by following reaction conversions with various catalysts. In the absence of both Ph2-BINOL and diamine ligands, the reaction of diethylzinc with benzaldehyde is very slow, exhibiting about 1% conversion after 8h at 0°C. When Ph2-BINOL was employed in the asymmetric addition to this substrate, the catalyst TOP increased exhibiting 25% conversion after 2 h. To evaluate the TOP of zinc centers bearing diimine derived from ethylene diamine and 2,4,6-trimethylbenzaldehyde (Table 4, entry 5) or the meso diamine (Table 5, entry 7), these ligands were... 

The meso-diamine is less soluble in Et20 than the dl-diamine. Therefore, dichloromethane is used to extract both isomers completely. 

This material is a mixture of dl-diamine meso-diamine N-methyl-benzylamine (approximately 82.6 4.4 13.0) as shown by1H NMR (see Note 8). 

Any commercial source of dl-tartaric acid works well. The ratio of tartaric acid to diamine is 1 1. The checkers found that if isomerization of the meso-diamine is incomplete, this purification procedure provides a mixture of meso- and dl-diamines. 

A07. Chatterjee, S.P.,B.K.Singh, andC.Gilvarg Biosynthesis of lysine in plants The putative role of meso-diamin-opimelate dehydrogenase Plant Mol. Bio. 26 (1994) 285-290. 

Scheme 41.55 Seidel s dual catalysis-based desymmetrization of meso-diamines.

Scheme 43.4 Catalytic enantioselective desymmetrization of meso-diamines by merging nucleophilic and HB catalysis.

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