Synthesis of chiral binol, article versions
Alkylation[ edit ] Pseudoephedrine amides undergo deprotonation by a strong base such as lithium diisopropylamide LDA to give the corresponding Z - enolates. Recently, the Wulff group has developed a robust catalytic asymmetric synthesis journal impact factor 2018 reaction providing optically active aziridines in high yields and selectivities.
Some of the commercially available oxazolidinone chiral auxiliaries.
Model for the stereoselectivity of an Evans aldol synthesis. Pseudoephedrine amides are typically prepared by acylation with an acid chloride or acid anhydride. However, for many transformations, the only available stereoselective methodology relies on chiral auxiliaries.
Model for the diastereoslective alkylation of a pseudoephedrine amide enolate. Scheme 1 back to top Asymmetric Aziridination Reaction Aziridines are important building blocks in organic synthesis because they allow for convenient access to amines, amino alcohols, diamines, and other useful nitrogen-containing molecules.
Condensation of tert-butanesulfinamide with aldehydes and ketones Synthesis of chiral amines[ edit ] Addition of a Grignard reagent to a tert-butanesulfinyl aldimine or ketimine results in asymmetric addition to give the branched sulfinamide. The auxiliary is subsequently removed e.
In the transition structure, the auxiliary carbonyl is oriented away from the enolate oxygen so as to minimize the net dipole of the molecule; one face of the enolate is blocked by the substituent on the chiral auxiliary.
Asymmetric synthesis[ edit ] Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers.
Racemic pseudoephedrine is marketed as Sudafed and under other brand names as a nasal decongestant. A positive non-linear effect was observed in the oxidation-kinetic resolution of thioanisole using this supported catalyst. After cleavage, the auxiliary can be recovered and reused.
The reaction relies on the addition of commercially available ethyl diazoacetate EDA to benzhydryl imines in the presence of arylborate catalysts prepared from vaulted aryl ligands and B OPh 3. Aldol reactions[ edit ] Chiral oxazolidinones have been employed most widely in stereoselective aldol reactions.
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