Amine protection, amide formation, imide formation, trifluoroacetic anhydride, pyridine, Wolff-Kishner reduction, phthalimide, hydrazine, nucleophilic addition, Lewis acid, Lewis base
Reader
Abstract
Contents
Extract
of 4
Abstract
This document outlines the mechanisms of protection and deprotection of amines, detailing the steps involved in protecting amine groups as amides and imides.
Contents
Protection as amide with pyridine and trifluoroacetic anhydride
Protection phase
Deprotection phase
Protection as imide
Phase de protection
Phase de déprotection
Protection as amide with pyridine and trifluoroacetic anhydride
Protection phase
Deprotection phase
Protection as imide
Phase de protection
Phase de déprotection
Get this table of contents for free after login.
Extract
[...] - Phase of deprotection The amides can hydrolyze in an acidic medium. Here, we have an attack of hydrazine on the carboxyl function of the phthalimide in 1. This reaction similar in the first steps to the Wolff-Kishner reduction, allows to weaken our protected amine group (transition from secondary to primary amine in 2). We then have the same type of intramolecular reorganization as in the protection step with a nucleophilic attack in 3 and the release of the original amine. [...]
[...] Finally, in a last step of deprotection, the previously protected function is recovered. These are phases that must be carried out with caution because we can potentially lose a lot of yield in these steps. Protection as amide (with pyridine and trifluoroacetic anhydride): - Phase of protection The first step is a classic nucleophilic addition on TFAA (trifluoroacetic anhydride) in dichloromethane solvent. An amide is produced and TFA (trifluoroacetic acid) is formed. Pyridine is a sufficient Lewis base to remove the proton from the secondary amine and thus obtain the stabilized amide function. [...]
