Redox amination, decarboxylative

A Brpnsted acid-catalysed decarboxylative redox amination converts 2-carboxyindoline (145) to an A-alkylindole (146), with an aldehyde as the source of the alkyl group. ... 

A Brpnsted acid-catalysed decarboxylative redox amination involving aldehydes with 2-carboxyindoline for the synthesis of A-alkylindoles has been described. The decarboxylative condensations of aldehydes with 2-carboxyindoline provide in situ azomethine ylides that undergo subsequent isomerization. 

The low specificity of electron-donating substrates is remarkable for laccases. These enzymes have high redox potential, making them able to oxidize a broad range of aromatic compounds (e.g. phenols, polyphenols, methoxy-substituted phenols, aromatic amines, benzenethiols) through the use of oxygen as electron acceptor. Other enzymatic reactions they catalyze include decarboxylations and demethylations [66]. 

The intermediate (32), produced upon decarboxylation of (31) may protonate at the a-carbon of the substrate (path a, Scheme 9), or at the 4 -carbon of PLP (path b). The hydrolysis of the aldimine produced by the former path accounts for the products of a-decarboxylation (equation 13). The hydrolysis of the aldimine produced in path (b) yields an aldehyde and pyridoxamine phosphate (PMP) (35). Note that this latter reaction, a decarboxylation-dependent transamination, may be classified as a redox process (reductive amination of PLP to PMP). 

---