Grignard reagents from methyl iodide

Pyrroles do not react with alkyl halides in a simple fashion polyalkylated products are obtained from reaction with methyl iodide at elevated temperatures and also from the more reactive allyl and benzyl halides under milder conditions in the presence of weak bases. Alkylation of pyrrole Grignard reagents gives mainly 2-alkylated pyrroles whereas N-alkylated pyrroles are obtained by alkylation of pyrrole alkali-metal salts in ionizing solvents. 

Hoshino and his co-workers reported that treatment of the Grignard reagent obtained from tryptamine (23), by the action of a suitable alkyl magnesium halide, with methyl iodide in benzene did not give the expected indolonino derivative 24 instead dinordeoxyeseroline (25) was obtained. 

B Add 30 g (II) over one-half hour to 420 ml methyl iodide and let stand fifteen hours at 5°. Separate the iodomethylate which precipitates, dry briefly at 50° and heat with vigorous stirring at 80° for two hours with 60 g NaCN in 1 L water. Extract with CHC13, dry and evaporate in vacuum the extract and dissolve the residue in 250 ml ether. Filter, evaporate in vacuum to a few ml and precipitate the acetonitrile (III) by adding petroleum ether. The acetonitrile can also be prepared directly from the indole via the Grignard reagent as given elsewhere here. 

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