Preparation of 3,4-enynoindoles via directed lithiation and application to the synthesis of 3,4-carbocycloindoles

Lithiation at C4 of the indole nucleus is readily directed by several functional groups. The 4-substituted indoles thus obtained are transformed into suitable substrates for metathesis reactions. Ring-closing metathesis effected on these compounds lead to skeletons related to several indole alkaloids.