RESUMEN
Gold-catalyzed oxidative [2+2+1] annulations between two imines and one α-cyano arylgold carbene afforded polyarylated imidazolium salts and molecular hydrogen efficiently. Control experiments suggest that the gold catalyst alone facilitates the main annulation, whereas Ag+ avoids the formation of inactive LAuCN. DFT calculations suggest that the success of this annulation relies on a 6 π-electrocyclization of cyano-free intermediates with cis-configured imines as initial reagents.
RESUMEN
Gold-catalyzed [3+2]-annulations of α-aryl diazonitriles with ynamides and allenamides yield 1-amino-1H-indenes in two distinct pathways; the success of these annulations relies on the high electrophilicity of α-cyano arylgold carbenes to activate an ionic pathway.
RESUMEN
Gold-catalyzed cycloadditions of ynamides with azidoalkenes or 2H-azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2H-azirine species afford pyrrole products with two regioselectivities when the Cß -substituted 2H-azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron-rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H-benzo[d]azepine products instead.
RESUMEN
The gold-catalyzed transformation of allenyl acetals into 5-alkylidenecyclopent-2-en-1-ones is described. The outcome of our deuterium labeling experiments supports a 1,4-hydride shift of the resulting allyl cationic intermediates because a complete deuterium transfer is observed. We tested the reaction on various acetal substrates bearing a propargyl acetate, giving 4-methoxy-5-alkylidenecyclopent-2-en-1-ones 4 via a degradation of the acetate group at the allyl cation intermediate.
RESUMEN
A world of possibilities: Gold-catalyzed reactions of 2-ethynylbenzyl ethers with organic oxides and α-diazoesters gave 1,3-dihydroisobenzofuran and naphthalene derivatives, respectively (see scheme; EWG = electron-withdrawing group). Mechanisms for the formation of the formal cycloadducts were elucidated by isotope labeling.
