Identificador: TDX:3037
Autors: Tan, Eric
Resum:
Alkynes are among the most versatile functional groups and are widely present in natural products, drugs, and organic materials. We became interested in new synthetic approaches towards building blocks containing acetylenes, by direct metal-catalyzed C-H alkynylation of functionalized molecules, using the functional group as handle for the introduction of alkynes.
In this thesis, we developed a catalytic system, based on ruthenium and rhodium catalysts, able to convert C(sp2)-H bonds into C(sp2)-alkyne bonds using a broad range of widely used functional groups, such as phenolic -OH, carboxylic acid, ester, ketone, ether, amine, thioether, sulfoxide, sulfone, phenol ester, carbamate, aldehyde and nitro groups. We next applied these reactions in the synthesis of polyaromatic hydrocarbons (PAH) such as extended fluoranthenes and dibenzopentalenes. The mechanisms of these alkynylation reactions were studied both experimentally and computationally, showing that the efficiency of these catalytic systems arises from two low-barrier steps: bromo-alkyne insertion into a ruthena- or rhoda-cycle, followed by bromide elimination. In the case of nitrobenzenes, we also observed an interesting electrophilic C-H rhodation process.
We next extended this catalytic system to the alkynylation of C(sp3)-H bonds using an iridium catalyst and oxime ethers or nitrogen heterocycles as directing groups.
Repositori URV