Polylithiumorganic compounds. Part 27: C,C-bond forming reactions of 3,4-dilithio-2,5-dimethyl-2,4-hexadiene

The reaction of the title compound 3,4-dilithio-2,5-dimethyl-2,4-hexadiene (4) with various mono- and bifunctional carbon-centered electrophiles is investigated, with special emphasis on carbonyl and carbonic acid derivatives. Depending on the nature of the electrophile, mono- and disubstituted derivatives with either butadiene, allene, or alkyne skeleton are obtained. Ring forming reactions in the second derivatization step are only observed in a few cases. Electrophiles bearing halogens as leaving groups react by a different mechanism and are not suitable in C,C-bond forming reactions. The compounds obtained in this investigation are suitable and highly reactive building blocks for further modifications. (C) 2000 Elsevier Science Ltd. All rights reserved.