Asymmetric Alkynylation of Seven-Membered Cyclic Imines by Combining Chiral Phosphoric Acids and Ag(I) Catalysts: Synthesis of 11-Substituted-10,11-dihydrodibenzo[b,f][1,4]oxazepine Derivatives

Asymmetric alkynylation of seven-membered cyclic imine dibenzo[b,f][1,4]oxazepines is successfully achieved by combining chiral phosphoric acid and Ag(I) catalysts. Various arylacetylenes, conjugated enynes, and terminal 1,3-diynes are good substrates for this reaction, and aliphatic hexyne is also a suitable donor at elevated temperature. Optimization of this approach has provided a facile method to synthesize optically active 11-substituted-10,11-dihydrodibenzo[b,f][1,4]oxazepine derivatives containing a carbon-carbon triple bond with 63-99% ee. Subsequent transformations of the carbon-carbon triple bond for the heterocyclic products have been disclosed.