Gold(I)- and Silver(I)-Catalyzed Heteroannulation Route to Isoquinoline-N-Oxides

Significance

Reported is the silver(I)- and gold(I)-catalyzed synthesis of isoquinoline-N-oxides from o-alkynylbenzaldoximines. The reaction was optimized with regards to catalyst and its scope was moderately investigated by variation of the terminal alkynic substituent. However, no aromatic substitution of the starting material was investigated. A reaction mechanism is not proposed but may be presumed to involve metal coordination to the alkyne followed by cyclization analogous to that proposed by Larock for a similar Pd-catalyzed sequence with imines (K. R. Roesch, R. C. Larock J. Org. Chem. 2002, 67, 86; also see review below).