Gold catalyzed cyclopropanation/[5+3] cycloaddition of 1,4,9- and 1,4,10-allenenynes to bicyclo[3.3.1]nonane derivatives

A synthetic method to prepare cycloalkyl‐ and (hetero)aryl‐fused bicyclo[3.3.1]nonane derivatives from gold(I)‐catalyzed cyclopropanation/[5+3] cycloaddition of 1,4,9‐ and 1,4,10‐allenenynes is described. The suggested double cycloisomerization mechanism delineates the first example of a stepwise [5+3] cycloaddition pathway in gold catalysis, a mode of reactivity that is also sparse in organic chemistry. Experimental and Density Functional Theory (DFT) computational studies based on a proposed gold carbenoid species provides insight into this unique selectivity that leads to the assembly of the architecturally challenging bridged carbocyclic motif.