Trans- -cyclohexanediamine

Denmark and coworkers [354] have examined the alkylation of a-lithiated benzyl carbanions generated from diastereoisomeric chiral phosphonamides 1.96 and 5.10. The stereoselectivity of this process depends on the configuration at phosphorus, and it is alway higher when starting from 1.96. It is believed that planar benzylic anions are alkylated on their least sterically hindered face. Strong support for this rationale derives from the X-ray crystal structure of A. After hydrolysis and treatment of the products with diazomethane, (R)- or (S)-dimethyl phosphonates can be obtained (Figure 5.6). Hanessian and coworkers [311, 312] performed similar alkylations of phosphonamides 1.74 (Y = Me, Cl) derived from (RJR)- or ( ,.S)-trans-cyclohexanediamines bearing a C2 axis of symmetry. The reaction of the intermediate anionic species on its less hindered face, followed by... 

Inspired by the primary aminocatalytic motif in nature, our group is interested in developing simple and efficient chiral primary amine catalysts. With Hine s pioneering contribution as a starting point, we developed simple primary-tertiary diamine catalysts derived from chiral tran -cyclohexanediamine such as 24 for asymmetric aldol reaction with excellent efficiency and enantioselectivity. 

Table 3 fists cycloaliphatic diamines. Specific registry numbers are assigned to the optical isomers of /n t-l,2-cyclohexanediamine the cis isomer is achiral at ambient temperatures because of rapid interconversion of ring conformers. Commercial products ate most often marketed as geometric isomer mixtures, though large differences in symmetry may lead to such wide variations in physical properties that separations by classical unit operations are practicable, as in Du Font s fractional crystallisation of /n t-l,4-cyclohexanediamine (mp 72°C) from the low melting (5°C) cis—trans mixture. 

Kmeshy et al. [96], for the first time reported recyclable catalyst based on polymeric Cr(lll)(X) salen complexes derived from (lR,2R)-(-)-cyclohexanediamine with 5,5 -methylene di-3- erf-butylsalicylaldehyde and X = Cl, NO3, and CIO4 67-69 (Figure 22). These complexes were used in regio-, diastereo-, and enantioselective aminolytic kinetic resolution (AKR) of fra 5-stilbene oxide, trans- S- methyl styrene oxide, and 6-CN-chromene... 

A similar situation occurs with the Co(III)-/ra>w-l,2-cyclohexanediamine-tetraacetic acid anion. Here only one conformation of the cyclohexane ring will allow the CDTA anion to coordinate as a sexadentate. If the other chair conformation is adopted, the two N atoms are now in trans axial positions and cannot coordinate bidentate to the Co(III) atom (Sec. III). 

For the bidentate chelating agents, x is S for the tridentate, x is 2. fchxn = trans-1,2-cyclohexanediamine. 

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