Chiral N‑Heterocyclic Carbene Gold Complexes: Synthesis, Properties, and Application in Asymmetric Catalysis

Nine new N-heterocyclic carbene gold chloride complexes (<b>10</b>–<b>18</b>) were synthesized starting from bulky chiral imidazolium salts (<b>1</b>–<b>9</b>) developed in this laboratory. Full characterization of all complexes, including the X-ray structures of gold­(I)­(1,3-bis­((<i>S</i>)-1-(2-methoxyphenyl)-2,2-dimethylpropyl)-1<i>H</i>-imidazol-2­(3<i>H</i>)-ylidene) chloride (<b>13</b>) and gold­(I)­(1,3-bis­((<i>S</i>)-2,2-dimethyl-1-(naphthalen-1-yl)­propyl)-1<i>H</i>-imidazol-2­(3<i>H</i>)-ylidene) chloride (<b>16</b>), is reported. The complexes <b>10</b>–<b>18</b> were applied in the methoxycyclization of 1,6-enynes using AgNTf₂ as an additive. Synthesis of the N-heterocyclic carbene gold triflimidate (<b>19</b>) was achieved by treating complex <b>12</b> with AgNTf₂. The complex gold­(I)­(1,3-bis­((<i>R</i>)-1-(2-methoxyphenyl)-2,2-dimethylpropyl)­imidazolidin-2-ylidene)­(1,1,1-trifluoro-<i>N</i>-(trifluoromethylsulfonyl)­methylsulfonamido) (<b>19</b>) was isolated and spectroscopically and structurally (X-ray) characterized