Amines as resolving agents

A Chiral Amines as Resolving Agents. Resolution of Racemic Acids... 

Salts of the various optically active aromatic acids and amines employed extensively as resolving agents frequently exhibit large nonequivalence (17,18,56-69). Since a fast-exchange process is... 

Nowadays, a variety of optically active amines and carboxylic acids are available as resolving agents.17,18... 

Resolving Agent for Certain lypes of Amines. TAPA has also been used as resolving agent for some amines that formed either unstable, insoluble, or noncrystalline salts with common resolving acids. Compounds (3) and (4) were among those resolved with TAPA, whereas camphor-10-sulfonic acid, 3-bromo-8-camphorsulfonic acid, 0,0-di-p-toluoyl-(+)-tartaric acid, (+)-tartaric acid, and (+)-camphoric acid could not be used. ... 

Other alkaloids such as brucine were used as resolving agents but their expense and extreme toxicity has made them unpopular and the availability of a range of amines (chapter 22), often made from the chiral pool, has made them unnecessary. 

N.CoKOtCIis - 0.5H2O, Cobaltatc(III), diam-mine(carbonato)dinitro-, cis.cis-, potassium, hemihydrate, 23 70 N4CoK08C2H<, 0.5H2O, Cobaltate(lll), diam-minedinitro(oxalato)-, cis.cis-, potassium, hemihydrate, 23 71 N4Co04QH, , Cobalt(Ill), bis(l,2-ethanedi-amine)(oxalato)-, as resolving agent, 23 65... 

Several types of asymmetric amine have been successfully resolved by fractional crystallization as lasalocid salts/ An improved synthesis of (/ )-(+)- and (5)-(—)-a-methyl-p-nitrobenzylamines and their use as resolving agents have been reported. ... 

Derivatization of the optically active aldehydes to imines has been used for determination of their enantiomeric excess. Chi et al.3 have examined a series of chiral primary amines as a derivatizing agent in determination of the enantiomeric purity of the a-substituted 8-keto-aldehydes obtained from catalysed Michael additions. The imine proton signals were well resolved even if the reaction was not completed. The best results were obtained when chiral amines with —OMe or —COOMe groups were used [2], The differences in chemical shifts of diastereo-meric imine proton were ca. 0.02-0.08 ppm depending on amine. This method has been also used for identification of isomers of self-aldol condensation of hydrocinnamaldehyde. 

For the synthesis of simple amines, including valuable resolving agents such as the (l-naphthyl)ethylamines, ATH can be useful but an N-hnked phosphorus-based electron withdrawing group was found to be a necessary addition to the substrate. Blacker and Martin demonstrated that the reduction may be run at very low levels of catalyst when triethylammonium formate was fed into the reactor and nitrogen gas passed into the system as shown in Figure 1.36. 

Other resolving agents are readily prepared from inexpensive chiral starting materials such as glucose, aspartic acid, or glutamic acid. A literature example is the use of /V-methylglucamine 6, obtained by reductive amination of D-glucose, in the resolution of naproxen (Chapter 6).13... 

Phenylethylamine (6), one of simple chiral amines, has been widely used as a resolving agent in the resolution of various kinds of racemic acids. There is a chiral carbon at the a-position, and a large phenyl group, a middle methyl group, and a small hydrogen atom are bonded to the carbon atom. One of... 

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