A facile approach to the synthesis of 5,7-disubstituted indoles via a highly selective lithium–bromine exchange of 5,7-dibromoindoles

A general approach to the synthesis of 5,7-disubstituted indoles has been developed based upon a highly selective lithium–bromine exchange reaction at the 7-position when 1-alkyl-5,7-dibromoindoles were treated with t-BuLi in ether. The resulting 5-bromo-7-lithiated indoles could react with various electrophiles to afford 5-bromo-7-substituted indoles (6) upon work-up. Without isolation of 6, the intermediates thus obtained could be exposed to a second lithium–bromine exchange reaction in a one-pot procedure and further reacted with various electrophiles to afford 5,7-disubstituted indoles (1).