Search results
Results from the WOW.Com Content Network
The reaction is generally performed in an aqueous solution at close to boiling. The first methylation of the amine begins with imine formation with formaldehyde. The formic acid acts as a source of hydride and reduces the imine to a secondary amine. Loss of carbon dioxide gas renders the reaction irreversible. Despite being more hindered, the ...
In recent years, several reagents such as Tris(2,2,2-trifluoroethyl)borate [B(OCH 2 CF 3) 3], [14] pyrrolidine [15] or titanium ethoxide [Ti(OEt) 4] [16] have been shown to catalyse imine formation. Rarer than primary amines is the use of ammonia to give a primary imine. [17] In the case of hexafluoroacetone, the hemiaminal intermediate can be ...
The first stage of the reaction is basic imine formation by the ketone group and the amine group of morpholine to give an enamine. This reacts as a nucleophile with electrophilic sulfur, similar to an Stork enamine alkylation reaction.
The intermediate imine can be isolated or reacted in-situ with a suitable reducing agent (e.g., sodium borohydride) to produce the amine product. [2] Intramolecular reductive amination can also occur to afford a cyclic amine product if the amine and carbonyl are on the same molecule of starting material.
In Mechanism I, the elimination occurs with imine formation after cyclization; while in Mechanism II, the elimination yields the nitrilium intermediate prior to cyclization. Currently, it is believed that reaction conditions affect the prevalence of one mechanism over the other (see reaction conditions ).
In 1950, Hurd and Strong reported [12] the first nitro-Mannich reaction using a preformed imine. Exposing an imine to a nitroalkane afforded a substituted beta-nitroamines in moderate yields. The moderate yields obtained when using the preformed imine could possibly be attributed to a competing decomposition pathway of the imine or the product.
Balanced equations for the individual steps are as follows. Imine formation through condensation: Me(Et)C=O + NH 3 → Me(Et)C=NH + H 2 O. Oxidation of the imine to the oxaziridine: Me(Et)C=NH + H 2 O 2 → Me(Et)CONH + H 2 O. Condensation of the oxaziridine with a second molecule of ammonia to give the hydrazone: Me(Et)CONH + NH 3 → Me(Et)C ...
The reaction is also stereoselective because the enamine addition occurs with a diastereomeric preference for trans addition without formation of the cis isomer. This is in contrast to traditional Diels–Alder reactions, which are stereospecific based on the alkene geometry. Scheme 2. regio- and diastereoselective Povarov reaction