Resolving agents, chirality

The initial concentration of the solution was 10.0 g of ( )-(62) in 50 g of acetone. In all runs, 10 mg of seed crystals were used. From the 10 runs highlighted in the 18.1, 21.0 g of /2-(-)-(62) of >92.0% ee and 21.4 g of (jS)-(+)-(62) of >90% ee are obtained from an input of 50.4 g of racemate. The table also nicely illustrates the continuous nature of the process, which coupled with the fact that no resolving agent, chiral auxiliary, enzyme, or catalyst is needed, underlines the economic advantages of this type of process. 

Hazardous Decomp. Prods. Thermal decomp, prods. CO, CO2, NOx during a fire, irritating/toxic NOx be generated NFPA Health 2, Flammability 2, Reactivity 0 Uses Emulsifier synthesis resolving agent chiral reagent... 

The other applications for cyclometalation reaction five-membered ring products include dendrimers [108-112], liquid crystals (metallomesogens) [113-116], resolving agents (chiral auxiliaries) [117-119], and photosensitizers for hydrogen production [120,121]. 

Ten Hoeve W, Wynberg H (1985) The design of resolving agents. Chiral cyclic phosphoric... 

Fig. 1-7. Racemic aminoacid derivatives resolved and chiral selector used as foaming agent.

The most direct method is the separation of the enantiomers by HPLC using chiral columns. It has the advantage that there is no risk of contamination from chiral resolving agents. The formation of diastereoisomers... 

Kagan and coworkers determined and studied in detail the crystal structure of a 1 1 molecular complex between (i )-methyl p-tolyl sulfoxide (10) and S)-N-(3,5-dinitrobenzoyl)-l-phenylethylamine (11). They suggested that amide 11, which had been used as a chiral solvating agent for sulfoxides, might find use as a resolving agent for these compounds. ... 

We have seen that the spectra of enantiomers, acquired under normal conditions, are identical. The NMR spectrometer does not differentiate between optically pure samples, and racemic ones. The wording is carefully chosen, particularly normal conditions , because it is often possible to distinguish enantiomers, by running their spectra in abnormal conditions - in the presence of a chiral resolving agent. Perhaps the best known of these is (-)2,2,2,trifluoro-l-(9-anthryl) ethanol, abbreviated understandably to TFAE. (W.H. Pirkle and D.J. Hoover, Top. Stereochem., 1982,13, 263). Structure 7.4 shows its structure. 

Optically pure mandelic acid (see Structure 7.6) can be a useful chiral resolving agent where the compound you are looking at has a basic centre, as it can form an acid-base pair with it, which is a stronger form of association. This compound is of sparing solubility in CDCI3 however and can precipitate out your compound if, as is often the case, its protonated form is of low solubility in CDCI3. 

In a related study, Rieke and Guijarro studied the configurational stability of the zinc-carbon bond in 2-butylzinc bromide and (l-phenylprop-2-yl)zinc bromide, using a bis(oxazoline) as a chiral resolving agent.72 From their data, the authors determined the A 6 of inversion at the secondary carbon of (l-phenylprop-2-yl)zinc bromide to be 113.8 kj mol-1. 

The absolute configurations of the products have now been determined (23) and the reaction promises to be of considerable interest, since Jacques and his colleagues have shown that chiral phosphoric acids are useful resolving agents (86). 

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