| Alkenylboronates are valuable reagents and versatile synthetic intermediates in organic synthesis. In this context, the hydroboration of alkynes has become one of the most straightforward and efficient methods for producing these molecules. However, most of the previous reports focus on the transformation of terminal acetylenes, while only limited examples of the hydroboration of unsymmetrical internal alkynes have been demonstrated. As such, the development of regiocontrolled hydroboration of internal alkynes still remains to be explored. This dissertation is devoted to the exploration of operationally simple methods for the synthesis of alkenylboronates featuring the Cu-catalyzed borylation of internal alkynes, which consists of two parts:Firstly, a Cu-catalyzed, divergent α- and β-selective borylation of ynamides with bis(pinacolato)diboron as the hydroboration reagent is reported, giving α-alkenylamide and (E)-β-alkenylamide boronates in excellent regio- and stereoselectivity under mild reaction conditions. This reaction is effective for different types of ynamides including N-sulfonyl, oxazolidinonyl, and pyrrolidinonyl ynamides. It provides a complementary regioselectivity to the existing methods for the preparation of trisubstituted alkenes.Secondly, a Cu-catalyzed borylative cycloisomerization of 1,6-enynes and related compounds has been developed, giving rise to 1,4-dienyl boronates in good to excellent yields with excellent regio- and stereoselectivity. The synthetic utility of this method is demonstrated by the Suzuki-Miyaura coupling of resultant products, which provides a highly regio- and stereoselective protocol for the preparation of stereocontrolled 1,4-dienes. It constitutes the first intramolecular allylborylation of alkynes, thus enhancing the scope of alkyne hydroboration methodology. |
