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Gold vinylidenes have recently emerged as useful intermediates in synthetic organic chemistry. These species, which can principally be accessed by a 1,2-migration process from a gold-activated alkyne or by dual gold catalysis on a diyne substrate, can react with nucleophilic partners or by C–H insertion to produce a variety of functionalized (poly)cyclic compounds. This short review covers the synthetic approaches developed so far to access gold vinylidenes and the different reactivities these species can exhibit. 1 Introduction 2 1,2-Migration Processes 3 Dual Gold Catalysis 4 Other Processes 5 Conclusion [ABSTRACT FROM AUTHOR]

Copper triflate mediated α-monohalogenation of α-diazo β-ketosulfones with ammonium halides provides the corresponding α-halo β-ketosulfones. Different metal triflates are investigated for this facile and efficient transformation. A plausible mechanism is proposed. [ABSTRACT FROM AUTHOR]

Significant enhancements in enantioselectivities and re-action efficiencies in asymmetric copper-catalysed C-H insertion and aromatic addition reactions of a-diazocarbonyl compounds in the presence of various group I salts are reported. For the first time in carbenoid chemistry, evidence for the critical role of the metal cation is described. [ABSTRACT FROM AUTHOR]