Figure 1: Combined Cu and NHC cooperative relay activation of alkynes as enolate equivalents. | Nature Communications

Figure 1: Combined Cu and NHC cooperative relay activation of alkynes as enolate equivalents.

From: Metal and carbene organocatalytic relay activation of alkynes for stereoselective reactions

Figure 1

(a) Alkyne and azide activated by Cu/NHC relay catalysis undergo formal [2+2] clycoaddition to give spiro-oxindole products. (b) Copper-catalysed [3+2] cycloaddtion of azide to alkyne gives triazole II that decomposes to ketenimine III with a release of N2. Addition of NHC to ketenimine III gives azolium enamide IV, which undergoes formal [2+2] cycloaddtion with isatin (or isatin–imine) to afford product V. NHC, N-heterocyclic carbene.

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