Since it's discovery independently by Sharpless and Meldal in 2002 the copper catalysed azide-alkyne cycloaddition (CuAAC) has become a ubiquitous molecular linking platform. Easy access to substituted 1,4-triazoles can be exploited to engender asymmetry to a myriad of potentially useful targets in high yields. Utilising the CuAAC to form chiral triazolic products in a single step is an attractive and powerful approach for the synthetic chemist. The area of asymmetric CuAAC is still in its infancy compared to more established asymmetric metal mediated transformations, however this leads to exciting challenges that need to be overcome to usher in the next era in the story of the triazole and click chemistry in general. This review details the steps taken into asymmetric CuAAC and the exciting results achieved thus far.
Herein we introduce tetrafluoropyridyl (TFP) as a new general protecting group for phenols. The TFP protecting group is readily cleaved under mild conditions.
The synthesis and kinetic resolution of quaternary oxindoles through copper catalysed azide-alkyne cycloadditions is presented. Selectivity factors (s) up to 22.1 ± 0.5 are reported. Enantioenriched alkynes and triazoles were obtained in ≥80% enantiomeric excess (e.e.).
The Negishi cross-coupling is a powerful C-C bond-forming reaction widely utilised in many areas of organic synthesis. This review details the use of Negishi cross-couplings in the synthesis of unnatural amino acids. The application of this reaction in the preparation of aromatic, heteroaromatic, and, complex amino acid derivatives are reviewed and presented herein.
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