Ai-Lan Lee

Cadiot–Chodkiewicz Active Template Synthesis of Rotaxanes and Switchable Molecular Shuttles with Weak Intercomponent Interactions

Weak interaction, switchable, rotaxane-based molecular shuttles, in which the positional fidelity of the macrocycle is conferred by a single hydrogen bond in each state, are constructed through the high-yielding and selective active template heterocoupling of different functionalized alkynes using the Cadiot–Chodkiewicz reaction

Gold catalysed reactions with cyclopropenes

Gold(i) catalyses the ring-opening addition of cyclopropenes in a mild and regioselective manner.

Divergent outcomes of gold(I)-catalyzed indole additions to 3,3-disubstituted cyclopropenes.

Depending on the conditions employed, gold(I)-catalyzed addition of indoles to 3,3-disubstituted cyclopropenes can be controlled to yield either 3-(E)-vinylindoles (3) or bis-indolylalkanes (4). If the cyclopropene substituents are sterically bulky, unprecedented gold-catalyzed oxidation under air occurs to yield bis-indolylalkene (5) and epoxide (6) at room temperature.

Gold(I) and Palladium(II) Complexes of 1,3,4-Trisubstituted 1,2,3-Triazol-5-ylidene “Click” Carbenes: Systematic Study of the Electronic and Steric Influence on Catalytic Activity

The synthesis of a small family of six electronically and sterically modified 1,3,4-trisubstituted 1,2,3-triazol-5-ylidene gold(I) chloride complexes is described. Additionally, the corresponding trans-[PdBr2(iPr2-bimy)(1,3,4-trisubstituted 1,2,3-triazol-5-ylidene)] complexes are also generated and used to examine the donor strength of the 1,3,4-trisubstituted 1,2,3-triazol-5-ylidene ligands. All compounds have been characterized by 1H and 13C NMR and IR spectroscopy, high-resolution electrospray mass spectrometry (HR-ESI-MS), and elemental analysis. The molecular structures of four of the gold(I) and four of the palladium(II) complexes were determined using X-ray crystallography. Finally, it is demonstrated that these 1,2,3-triazol-5-ylidene gold(I) chloride complexes (Au(trz)Cl) are able to catalyze the cycloisomerization of 1,6-enynes, in high yield and regioselectivity, as well as the intermolecular direct etherification of allylic alcohols. Exploiting the Au(trz)Cl precatalysts allowed the etherification of allylic alcohols to be carried out under milder conditions, with better yield and regioselectivity than selected commercially available gold(I) catalysts.

Gold(I)-catalysed alcohol additions to cyclopropenes

Gold(i)-catalysed addition of alcohols to 3,3-disubstituted cyclopropenes occurs in a highly regioselective and facile manner to produce alkyl tert-allylic ethers in good yields. The reaction is tolerant of sterically hindered substituents on the cyclopropene as well as primary and secondary alcohols as nucleophiles. In this full article, we report on the substrate scope and plausible mechanism, as well as the regioselectivity issues arising from subsequent gold(i)-catalysed isomerisation of tertiary to primary allylic ethers.

Regioselective synthesis of tert-allylic ethers via gold(I)-catalyzed intermolecular hydroalkoxylation of allenes.

A highly regioselective method towards tertiary allylic ethers via gold(I)-catalyzed intermolecular hydroalkoxylation of allenes is disclosed. Preventing subsequent isomerization of the tertiary allylic ether products to primary allylic ethers appears to be the key to achieving high regioselectivities.

Palladium-Catalyzed Direct C-H Functionalization of Benzoquinone.

A direct Pd-catalyzed C=H functionalization of benzoquinone (BQ) can be controlled to give either mono- or disubstituted BQ, including the installation of two different groups in a one-pot procedure. BQ can now be directly functionalized with aryl, heteroaryl, cycloalkyl, and cycloalkene groups and, moreover, the reaction is conducted in environmentally benign water or acetone as solvents.

Ligand- and Base-Free Pd(II)-Catalyzed Controlled Switching between Oxidative Heck and Conjugate Addition Reactions

A simple change of solvent allows controlled and efficient switching between oxidative Heck and conjugate addition reactions on cyclic Michael acceptor substrates, catalyzed by a cationic Pd(II) catalyst system. Both reactions are ligand- and base-free and tolerant of air and moisture, and the controlled switching sheds light on some of the factors which favor one reaction over the other.

Gold(I)-Catalyzed Addition of Thiols and Thioacids to 3,3-Disubstituted Cyclopropenes

Gold(I)-catalyzed reactions of thiols, thiophenols, and thioacids with 3,3-disubstituted cyclopropenes occur in a regioselective and chemoselective manner to produce either vinyl thioethers or primary allylic thioesters in good yields. A survey of commonly used gold(I) catalysts shows Echavarrens cationic gold(I) catalyst to be most tolerant of deactivation by sulfur. A novel digold with bridging thiolate complex is characterized by X-ray crystallography, shedding light on a possible deactivation pathway.

Deactivation of gold(I) catalysts in the presence of thiols and amines – characterisation and catalysis

Thiols and amines, which are common heteroatom nucleophiles in gold-catalysed reactions, are known to dampen the reactivity of gold catalysts. In this article, the identity and activity of gold(I) catalysts in the presence of thiols and amines is investigated. In the presence of thioacid, thiophenol and thiol, digold with bridging thiolate complexes [{Au(L)}2(μ-SR)][SbF6] are formed and have been fully characterised by NMR and X-ray crystallography. In the presence of amines and anilines, complexes [LAu-NH2R][SbF6] are formed instead. All new isolated gold complexes were investigated for their catalytic activity in order to compare the level of deactivation in each species.