Alkyne functionalization is a hot topic in organic synthesis because of its diverse transformations for the access to different classes of compounds. Among those transformations, copper-catalyzed hydroboration of alkynes is captivating to scientists owing to the usefulness of vinyl boronates as building blocks in organic synthesis. The main theme of this thesis work focuses on the synthesis of 1,3,5-trienes via one-pot Cu-catalyzed hydroboration and Pd-catalyzed Suzuki–Miyaura cross-coupling using an Aphos ligand as the common ligand without separating the alkenyl boronate intermediate. A brief introduction is given in Chapter 1, detailing with the most recent progress in the development and application of copper(I)-catalyzed hydroboration of internal alkynes in total synthesis...[ Read more ]

Alkyne functionalization is a hot topic in organic synthesis because of its diverse transformations for the access to different classes of compounds. Among those transformations, copper-catalyzed hydroboration of alkynes is captivating to scientists owing to the usefulness of vinyl boronates as building blocks in organic synthesis. The main theme of this thesis work focuses on the synthesis of 1,3,5-trienes via one-pot Cu-catalyzed hydroboration and Pd-catalyzed Suzuki–Miyaura cross-coupling using an Aphos ligand as the common ligand without separating the alkenyl boronate intermediate. A brief introduction is given in Chapter 1, detailing with the most recent progress in the development and application of copper(I)-catalyzed hydroboration of internal alkynes in total synthesis, as well as the one-pot strategies for the synthesis of conjugated alkenyl units.

Internal alkynes without significant steric or electronic bias are the challenging substrates for the copper-catalyzed hydroboration. Chapter 2 showcases the results of application of the one-pot Cu-catalyzed hydroboration and Pd-catalyzed Suzuki–Miyaura cross-coupling for the synthesis of 1,3,5-trienes. It further expands the scope of unsymmetrical internal alkynes, including a variety of enynes, without significant electronic and steric effects in the hydroboration using 2-(diisopropylphosphino)-N,N-diisopropylbenzamide (Aphos^ip-H), one of our group’s aromatic amide-derived phosphane (Aphos) family of ligands. The alkenyl boronate products are efficiently obtained with good regioselectivity and moderate yields. The synthesis of conjugated polyene molecules is challenging since they are light-sensitive and cannot withstand high temperatures and acidic/basic conditions. After exploring the suitability of a wide scope of unsymmetrical internal alkynes, the one-pot Cu-catalyzed hydroboration and Pd-catalyzed Suzuki–Miyaura cross-coupling using Aphos^ip-H as the common ligand has been established for an easy access to different 1,3,5-trienes under mild conditions. The alkenyl boronates without isolation undergo coupling reaction with alkenyl halides in the presence of a weak base (K₃PO₄·3H₂O) at 35 ºC to furnish 1,3,5-trienes. Finally, the one-pot synthesis has been illustrated in the synthesis of some selected 1,3-dienes.