THESIS
2020
xiv, 123 pages : illustrations ; 30 cm
Abstract
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...[
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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 (K
3PO
4·3H
2O) 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.
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