Ru(0)-Catalyzed Regioselective Synthesis of Borylated-1,4- and -1,5-Diene Building Blocks

Abstract

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.

Ru(0)-catalysed synthesis of borylated polyene building blocks by cross-dimerisation toward cross-coupling

“…3.2. Reaction mechanisms giving borylated 1,4-and 1,5-dienes 22 In order to understand the mechanism, we tried the stoichiometric reaction [Ru(Z 4 -cisoid-1,3-pentadienylB(pin))(1,5-cod)(NCMe)] with vinylB(dan), which is expected to give 52 (Table 2) according to the 1 H NMR experiment. However, a complex mixture was formed and no useful information was obtained.…”

Chemoselective Coupling of π‐Systems to Access Metallated 1,4‐ or 1,5‐Skipped Dienes in Multicomponent Reactions

“…For instance, the investigation of synthetic routes toward biologically active molecules containing skipped diene units remains continuously interesting and important (Figure 1). [3b–d] Therefore, the considerably diverse chemistry of 1,n‐dienes, particularly 1,4‐ and 1,5‐dienes, functionalized with main group elements (in particular, boron and silicon) is rapidly expanding (Scheme 1A), as evidenced by the dozens of regio‐ and stereoselective C−[Si] and/or C−[B] bond‐forming reactions accompanied by concurrent C−C bond formation.…”