Tandem intramolecular carbolithiation-transmetallation: from lithium to copper or boron chemistry

Lithium/copper transmetallation from the organolithium intermediate 3 (obtained via intramolecular carbolithiation of the acyclic organolithium 2, generated by a chlorine-lithium exchange) gives the corresponding organocopper intermediate 5. This intermediate reacts with eletrophiles, such as allylic or propargylic halides, acyl chlorides or alpha,beta-unsaturated carbonyl compounds giving the expected compounds 6-10, which are not possible to be obtained directly from the organolithium 3. On the other hand, lithium/boron transmetallation affords the corresponding alkylboronic acid 11 which, after palladium-catalysed Suzuki-Miyaura cross-coupling reaction with different aryl bromides gives the expected products 12 with modest yields, the corresponding Ullman biarylic homocoupling products being the major by-products. (C) 2005 Elsevier Ltd. All rights reserved.