ELECTROPHILIC SUBSTITUTIONS AND ADDITIONS TO ENAMINES

Research Department Agricultural Division Monsanto Company St. Louis, Missouri 

Reaction with Carboxylic Acid Chlorides, Anhydrides, and Ketenes 135 

Enamines have a three-atom tt system and are thus in principle capable of reaction with an electrophile on nitrogen or on carbon as shown by the mesomeric forms (1) and (2), 

It might also be expected that enamines would be less basic than the corresponding saturated tertiary amines as a consequence of the delocalization of the nonbonded electron pair of the nitrogen. The older literature (/—/), which involved measurements in aqueous or partly aqueous solution, led to the opposite conclusion. This unexpected increase in basicity was rationalized in terms of an equilibrium between the enamine and the quaternary iminium hydroxide  

Recent work (5) using kinetic methods has shown that the enamines derived from isobutyraldehyde are indeed less basic than the corresponding saturated tertiary amines. 

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