We aim to develop new methods for the preparation of aryl-substituted furanones and pyrrolinones. As part of this program, we report now our exploration into the Lewis acid-mediated Friedel-Crafts reactions of indoles with simple furanones and simple N-substituted pyrrolinones. The synthesis of the latter was investigated using pyrrole-2-carboxaldehydes and a variety of oxidants and N-protecting groups. The best results were obtained with N-sulfonyl as the protecting group and m-CPBA as the oxidant. The direct indolylation of furanone and pyrrolinones was explored with a variety of Lewis acids. In the case of furanones, modest yields of the expected 4-(indol-3’-yl)butyrolactones were obtained; these compounds could be oxidized into the corresponding furanones using DDQ. In some cases with the Freidel-Crafts reaction with furanone, a fused indole byproduct (carbazolone) was obtained in low yield. In the case of Friedel-Crafts reactions involving N-sulfonylpyrrolinone, unexpectedly, no Friedel-Crafts products were observed.

Investigation into the friedel-crafts alkylation of indoles with simple furanones and pyrrolinones

ACS Spring Meeting 2021

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