Au(I)-catalyzed cycloaddition pathways of non-terminal propargyl substrates

Abstract

Novel chiral menthol-based pyridyl nitrone ligands were synthesized and Au(I) coordination of the ligands gave chiral Au(I)–nitrone complexes. 1H NMR studies of the gold(I) coordination experiments with nitrone ligands afforded a convenient method for monitoring complex formation. The catalytic effect of Au(I)–nitrone complexes, shown to tune catalytic systems to produce uncommon products, was evaluated in [2 + 2 + 2] cyclotrimerization and [2 + 4] cyclodimerization reactions of non-terminal propargyl acetals. Alternative gold(I)-catalyzed [2 + 2], [2 + 4] and [3 + 4] cycloaddition reaction pathways of non-terminal propargyl acetals with imine substrates gave a diverse range of N-heterocyclic products. The present screening study demonstrates the potential and the versatility of non-terminal propargyl acetals in gold(I)-catalyzed cycloaddition reactions.