Vinylation of Nitro‐Substituted Indoles, Quinolinones, and Anilides with Grignard Reagents

Abstract

The reaction of vinyl Grignard reagents with o-methoxynitroarenes containing an electron-releasing substituent para to the nitro group proceeds through a pathway that is different from the initially expected Bartoli indole synthesis. Thus, instead of giving fused indole derivatives, these reactions provide a very mild and efficient new procedure for the synthesis of synthetically relevant aromatic systems containing an o-nitrovinyl moiety, such as 5-nitro-4-vinylindoles, 6-nitro-7-vinylindoles, 6-nitro-5-vinyl-2(1H)quinolinones, and 4-nitro-3-vinylanilines.

Applications of Bartoli indole synthesis

“…70,71 Considering the high stabilization of dinitrobenzene radical anions, 72 the occurrence of the reaction is quite surprising.…”

Aryl Grignard Reagents in Chemodivergent N‐ and C‐Arylations: Concise Access to Two Families of Tetracyclic Fused Carbazoles from 6‐Nitroquinolines

“…On the other hand, the less hindered 2‐naphthylmagnesium bromide gave a mixture of compounds 6j and 7j . It is pertinent to mention that the reaction between compound 4 and the less hindered vinylmagnesium bromides exclusively afforded 5‐vinylindoles 12. The diarylamine structure of compounds 6 was deduced from spectroscopic data and confirmed by the independent synthesis of compound 6d .…”

“…The preparation of the starting material is summarized in Scheme . Compound 3 was prepared by N ‐methylation of 5 under phase‐transfer catalysis conditions, using our previously published procedure 12. The synthesis of 4 was achieved by O ‐methylation of 5 with methyl iodide in the presence of silver oxide as the base.…”

Synthesis of diverse indole libraries on polystyrene resin – Scope and limitations of an organometallic reaction on solid supports

“…Two exceptions were the hydroxycarboxylic acids 1{f} , 1{j} and the methoxycarboxylic acids 1{g} , 1{k} , which all failed in that very complex mixtures were obtained. Recently, it was reported that methoxynitroarene gave somewhat different products in the presence of Grignard reagent [48]. …”