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FISCHER INDOLE SYNTHESIS OF 3-BENZYL-1H-INDOLE VIA CONDUCTIVE AND DIELECTRIC HEATING

Jesco Panther, Julian Rechmann, Thomas J. J. Müller
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Abstract


As a part of designing one-pot synthesis conditions for a combination of Heck isomerization and Fischer indolization (HIFI sequence), a model reaction was studied using 3-phenylpropanal and phenylhydrazine to furnish 3-benzyl-1H-indole under conductive and dielectric heating. While Amberlyst® 15 as an acidic catalyst or T3P® (propylphosphonic acid cyclic anhydride) as a condensation agent gave high yields of 3-benzyl-1H-indole under both conductive and dielectric heating, these agents were not compatible with the conditions of the initial Heck isomerization. However, the catalyst-free thermal process for the indolization step proceeded with good yields in conjunction with the preceding Heck isomerization in a one-pot process under dielectric heating in N-methylpyrrolidone as a solvent.

 


Keywords


indole; acid catalysis; condensation; Fischer indole synthesis; Heck isomerization; microwave-assisted reactions; one-pot reactions; thermal reactions

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