Peri-Directed 7-Substitution in η6-Indoletricarbonylchromium(0) Complexes

Article abstract of DOI:10.1016/S0040-4020(01)89122-5

7-Substituted indoles were prepared by the lithiation - electrophilic quenching of 1-methyl-, 1-methoxymethyl-, and 1-(2-trimethylsilylethoxymethyl)indoletricarbonylchromium(0) complexes.C-2 of the 1-methylindole series had to be blocked to achieve subsequent 7- (and 4-) metallation, but the other series could be directly metallated at C-7 without attack at C-4 by 1-alkoxymethyl directed lithiation.Metallation at C-2 in the 1-alkoxymethyl series was avoided by the use of 2-trimethylsilyl or the 3-methyl analogues.No conditions were found to effect the removal of the methoxymethyl group, but the 2-trimethylsilylethoxymethyl group was efficiently cleaved with 'anhydrous' tetrabutylammonium fluoride.