Racemic methylations, order catalyst

Vlhen the chiral methylation is carried out with 30% aqueous NaOH the indanone is deprotonated at the interface but does not precipitate as the sodium enolate (Figure 11). In this system there are 3 to 4 molecules of H2O per molecule of catalyst available while in the 50% NaOH reactions the toluene is very dry with only 1 molecule of H2O available per catalyst molecule thus forcing the formation of tight ion pairs. Solvation of the ion pairs in the toluene/30% NaOH system should decrease the ee which we indeed observe with an optimum 78% versus 94% in the 50% NaOH reaction. In the 30% NaOH reactions the ee decreases from 78% to 55% as the catalyst concentration increases from 1 mM to 16 mM (80 mM 5, 560 mM CH3CI, 20 C). Based on these ee s rates of formation of (-h)-enantiomer and racemic product can be calculated. When the log of these rates are plotted versus the log of catalyst concentrations (Figure 13) we find an order of about 0.5 in the catalyst for the chiral process similar to that found using 50% NaOH consistent with a dimer-monomer pre-equilibrium. The order in catalyst for the... 

Figure 13. Order in catalyst for racemic (1.0) and chiral (0.5) methylations using 30% NaOH.

In order to obtain a commercially viable process it is necessary to racemize the unwanted amine enantiomer, preferably in situ in a so-called DKR. The paUadium-on-charcoal-catalyzed racemization of amines was first reported by Murahashi et al. [23] and was later combined with Upase-catalyzed acylation, to afford a DKR, by Reetz [24] and others [25]. We were able to achieve a DKR of a-methyl benzyl-amine by performing the hpase-catalyzed acylation in the presence of a palladium nanoparticle catalyst (Scheme 6.10). 

The failure in separating in fractions possessing optical activity of opposite sign the stereoregular polymers of racemic 5-methyl-l-heptene, polymerized in the presence of the same catalyst as that used to prepare polymers from racemic 3-methyl-l-pentene and 4-methyl-1-hexene (75), might be an indication that, in order to obtain prevailingly (R) and (S) separable polymers instead of random copolymers from racemic vinyl monomers, the asymmetric carbon atom of the monomer must be in a or in / position with respect to the double bond. 

Overberger et al [59] reported on the polymerization of D(-)-j3-methyl-e-caprolactam (XXVIII) into a crystalline polymer. A study of solution properties of the polymer has shown that no ordered helix structure exists, that solvatation of the amide carbonyl is independent of polymer conformation, and that each mer is solvated independently. — OA a, j3, 7, and 5 methyl-e-caprolactams have been successively polymerized by Overberger et al [60] OA a-methyl-e-caprolactam racemized under polymerization conditions, i.e. in the presence of sodium hydride catalyst. 

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