A series of borylated conjugated trienes and skipped dienes is prepared by Ru-catalysed cross-dimerisation using alkynyl-, dienyl-, and vinyl boronates.

A new methodology for preparation of borylated-1,4-and -1,5-diene building blocks is established. Ru(0)-catalyzed cross-dimerization of (1E,3E)-penta-1,3-dien-1-ylboronic acid pinacolate ester (2b) with but-3-en-2-one (3a) selectively gives a borylated-1,4-diene product, (3E,6E)-5-methyl-(4,4,5,5-tetrameth-) also gives a borylated-1,4-diene product. These crossdimerizations give mono-borylated-1,4-dienes, yet cross-dimerizations using (1E,3E)-penta-1,3-dien-1-ylboronic acid pinacolate ester (2b) with vinyl B(dan) (3i) produce a diborylated-1,5diene. Selective formation of 1,6-diborylated-1,5-dienes is unprecedented, and a series of diborylated-1,5-dienes can be used as building blocks for Suzuki−Miyaura cross-coupling reactions. As an application of the present method, the formal synthesis of racbongkrekic acid, a strong inhibitor of the adenine nucleotide translocator, has been achieved.