Synthesis and lithiation oftricarbonyl(methylbenzo[b]thiophene)chromium complexes

Lithiation of tricarbonyl(benzo[b]thiophene)chromium with Buⁿ Li followed by methylation with MeI gives successively 2-methyl- and 2,7-dimethyl-substituted derivatives. Similarly, 3-, 4-, 5-, 6- and 7-methyl derivatives gave 2,3-, 2,4-, 2,5- and 2,6-dimethylbenzo[b]thiophenetricarbonyl complexes, whereas the 2-methyl derivative gave 2,7-dimethylbenzo[b]thiophenechromium tricarbonyl, selectively. © 1987.