1,1-dimetallic reagents for the elaboration of stereoselectively di- or trisubstituted linear substrates

Although gem-dimetallic species have been known for a long time, and reacted once or twice with electrophiles, the allyl zincation of substituted vinyl metals has emerged as a particularly efficient access to such species. This is due to a high face selectivity, in the addition to the C=C bond, which can be governed by vicinal or more remote heteroatoms. This strategy has some aspects in common with the well-known allylations or aldol condensations to carbonyl derivatives. But in the present case, the C=C bond has a low polarity. We present here some examples which lead to dior polysubstituted linear substrates, of given geometry, where the organodimetallic obtained has been doubly protonated. by water. Further elaborations (to alkenes, ketones, etc.) are possible.