Enecarbamates reactions with electrophiles

Although the nucleophilic reactivity is generally less than that of the enamine, one of the typical reactions of the enecarbamates and enamides is the reaction with electrophiles at the -position (equation 8). Since this review deals with electrochemistry, chemical reactions of enecarbamates and enamides are not included but some of them are summarized elsewhere9. The oxidation potentials of enecarbamates are more positive than those of enamines (EJV vs SCE, 7 = 1.59 V 8 = 1.37 V in CH3CN-0.1N LiC104, 100 mV/s). 

Scheme 9 demonstrates the further synthetic application of the thus obtained N,0-acetals. Substitution of the alkoxy or acyloxy group by nucleophiles like enol ethers, enol esters, enamines, other electron-rich olefins, CH-acidic compounds, electron-rich aromatics, isocyanides, trimethylsilyl cyanide, organometallics, vinyl and allyl silanes, hydroxy functions, or trialkylphosphites either catalyzed by Lewis acids or proton acids leads to the product of the amidoalkylation reaction (path a). In the presence of stereocenters as control elements, diasteroselective amidoalkylation reactions can be performed as shown in a large number of examples. On the other side, as Nyberg showed for the first time [196], elimination with formation of enecarbamates [208] and enamides [196,208,209] followed by reaction with electrophiles or nucleophiles (path b) also is possible. 

The formation of a carbon-carbon bond at the p-position of amines is made possible by the reaction of these enecarbamates with electrophiles. The acylation, Vilsmeyer reaction and hydroboration at the P-position of carbamates have been achieved by using this technique31. The syntheses of a derivative of hydrolulolidine 49 and nicotin-aldehyde 50 are shown below as typical examples. 

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