Selective functionalization of alkynes and allenes

Abstract

Alkynes and allenes are important building blocks in organic synthesis and serve as synthons for a wide range of chemical transformations. Among them, in particular, ynones, propargylic acetates, ynamide and allenamides, can exhibit high levels of regio- and stereoselectivity in their functionalization reactions, presumably due to the fact that their π bonds are more or less polarized. The development of transformations of alkynes and allenes has gained significant progress. Nevertheless, new synthetic applications and reaction modes remain in high demand owing to their importance in organic synthesis. In Chapter 1, a highly efficient and regioselective ruthenium-catalyzed C(sp³)—H borylation has been developed. Furthermore, the mild reaction conditions demonstrate impressive tolerance towards a wide range of functional groups, albeit with limited substrate scope. Control experiments and deuterated experiments have provided insights into an unconventional mechanism for the reaction. In Chapter 2, a novel reaction mode for the hydroboration of propargylic carbonates is described. The catalyst employed in this process is [CpRu(MeCN)₃]PF₆. When propargylic carbonates are subjected to hydroboration under these conditions, allylboronate products are obtained. Additionally, the reaction exhibits good chemo-, regio-, and stereoselectivity. In Chapter 3, Pd-catalyzed disilylation of ynamides is described. The tri- and tetra-substituted enamide derivatives could be obtained in a remarkably regio- and stereoselective manner. Furthermore, it has been demonstrated that the resulting disilylated enamide products can be effectively used as versatile building blocks in organic synthesis. In Chapter 4, a Ru-catalyzed intermolecular cyclopropanation of allenamides with N₂CHTMS is described. This process allows direct access to functionalized methylenecyclopropanes. The methylenecyclopropane products can be formed in good yields and with remarkable reigo- and diastereo- selectivities.

Date of Award	2023
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Jianwei SUN (Supervisor)