Synthesis of 2-(Indol-3-yl)-ethanone-based Arylhydrocarbon Receptor Agonist Candidates via Weinreb Amides of Indole-3-acetic Acid.

Grignard reactions with the Weinreb amide (N-methoxy-N-methylamide) of indole-3-acetic acid provide a facile access to indol- 3-yl ketones, which are potential agonists of the human aryl hydrocarbon receptor ("dioxin receptor"). Addition of one equivalent of the MgBr2•THF complex avoids discolorations and oxidative side reactions, for which the 3-indolyl system is notorious. The product ketones carry aliphatic, olefinic, as well as (hetero)aromatic residues. The reaction conditions were thoroughly optimized, and full sets of analytical data including example crystal structures are presented.