The ligand exchange reaction between Au38(2-PET)24 (2-PET: 2-phenylethanethiolate) clusters and enantiopure planar chiral [2.2]paracyclophane-4-thiol 1 (PCP-4-SH) was studied using High Performance Liquid Chromatography (HPLC) and mass spectrometry. It is shown that even at the initial stage of the reaction at least three out of the four symmetry-unique sites are exchanged leading to different regioisomers of composition Au38(2-PET)23(PCP-4-S)1. Using HPLC it was possible to isolate one specific regioisomer. The latter is stable at room temperature and at slightly elevated temperatures. However, at 80° C the adsorbed thiolate (PCP-4-S) moves between different symmetry-unique sites. These observations have implications for the preparation of mixed ligand shell clusters with specific ligand patterns
The preparation of a series of new prochiral bis-alkynes is reported. A selection of chiral ligands is examined to gain additional information about the scope of the new asymmetric Huisgen 'click' reaction [the desymmetrisation of bis-alkynes using chiral ligands in conjunction with the widely applied copper-catalysed azide-alkyne cycloaddition (CuAAC) triazole synthesis]. The development of a new chiral assay for (±)-methyl 2-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-2-cyanopent-4-ynoate, and the production of this mono-triazole in up to 18% enantiomeric excess is described.
An expeditious route to planar chiral sulfur-based scaffolds has been achieved in two operational steps from cheap and commercial [2.2]paracyclophane hydrocarbon. The sulfur atom was introduced in a specific benzylic position of the [2.2]paracyclophane according to a reductive sulfanylation reaction, which proceeds under two complementary reaction conditions with either the BF3•OEt2/Et3SiH or TFA/BH3 . THF combinations. The study was completed by the development on a highly efficient resolution approach by HPLC.
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