Efficient Synthesis of Isoquinoline Derivatives via AgOTf/Cu(OTf)₂-Cocatalyzed Cyclization of 2-Alkynyl Benzaldoxime

Abstract

An efficient, AgOTf and Cu(OTf)₂ multicatalytic intramolecular cycloisomerization of 2-alkynylbenzaldoxime is reported. Isoquinoline N-oxides have been found to be deoxygenated to the corresponding quinolines in good yields in dimethylformamide/dichloroethane (v/v 5:1) as solvent at 120 °C.

GRAPHICAL ABSTRACT

Keywords:

• Intramolecular cycloisomerization
• isoquinoline
• isoquinoline N-oxide
• multicatalytic deoxygenation

ACKNOWLEDGMENTS

We thank the National Natural Science Foundation of China (21072102), the Committee of Science and Technology of Tianjin (11JCYBJC04200), and State Key Laboratory of Elemento-organic Chemistry in Nankai University for financial support.

Notes

^a Unless otherwise noted all the reactions were performed with 0.5 mmol of 2a and 10 mol% catalyst in 5 ml solvent at 120 °C.

^b DMF/DCE (v/v = 1:1).

^c DMF/DCE (v/v = 1:3).

^d DMF/DCE (v/v = 1:5).

^e Isolated yields.

^a Unless otherwise noted all the reactions were performed with 0.5 mmol of 2 and 10 mol% AgOTf along with 10 mol% Cu(OTf)₂ in 2 ml DMF and DCE (v/v = 5:1) at 120 °C for 24 h.

^b Isolated yields.