Synthesis of 1-Aroxyisoquinolines from Phenols and 2-Alkynylbenzaldoximes

Abstract

Reported is the silver-catalyzed synthesis of 1-aroxyisoquinolines from 2-alkynylbenzaldoximes and phenols in the presence of PyBroP. This work is a direct extension of other ­recent work by the same authors (D. Zheng, Z. Chen, J. Liu, J. Wu Org. Biomol. Chem. 2011, 9, 4763), where amines were used instead of phenols to prepare 2-aminoisoquinolines. This previous work itself was based on the known silver-catalyzed formation of isoquinoline N-oxides from benzaldoximes (H.-S. Yeom, S. Kim, S. Shin Synlett 2008, 924), and the amination of isoquinoline N-oxides using PyBroP (A. T. Londregan, S. Jennings, L. Wei Org. Lett. 2010, 12, 5254). The proposed mechanism is directly analogous to the mechanism of the previously reported reaction, which combined the two known mechanisms of the individual steps. As in the previous work, there is no explanation for the requirement of two equivalents of PyBroP.