One-Pot Tandem Nickel-Catalyzed α‑Vinyl Aldol Reaction and Cycloaddition Approach to [1,2,3]Triazolo[1,5‑<i>a</i>]quinolines

A one-pot tandem approach to [1,2,3]triazolo[1,5-a]quinolines was developed from (E)-β-chlorovinyl ketones and 2-azidoaryl carbonyls using a sequence of α-vinyl aldol and azide–alkyne cycloaddition reactions. In particular, the intramolecular azide–alkyne cycloaddition of allenol intermediates was readily promoted by a synergistic action of NEt3 and nickel catalysts. Given that the [1,2,3]triazolo[1,5-a]quinolines are useful synthetic precursors to α-diazoimines through ring–chain isomerization process, the subsequent denitrogenative transformations should provide ready access to valuable heterocyclic compounds.