Palladium-catalyzed oxidative ortho-acylation of 2-arylbenzoxazoles and 2-arylbenzothiazoles with toluene derivatives
作者:Yong Zheng、Wei-Bin Song、Shu-Wei Zhang、Li-Jiang Xuan
DOI:10.1016/j.tet.2015.01.025
日期:2015.3
A palladium-catalyzed oxidative ortho-acylation of 2-arylbenzoxazoles and 2-arylbenzothiazoles using TBHP as oxidant was developed, in which readily available toluene derivatives were used as the in situ generated acyl sources. This reaction afforded the desired products in moderate to good yields, and exhibited excellent regioselectivity. The plausible mechanism was also proposed.
An efficient and facile catalytic protocol for benzoxazole-directed ortho-acylation of 2-arylbenzoxazoles has been described using aldehydes as the easily accessible acyl source. This catalytic system was performed in the presence of tert-butyl hydroperoxide (TBHP) as the oxidant in chlorobenzene, affording the acylated 2-arylbenzoxazoles in moderate to good yields. The acylation exhibited high regioselectivity for the substrates containing a meta-substituent in the benzene ring and typically occurred at the less sterically hindered ortho-C-H bond of the directing group. (C) 2012 Elsevier Ltd. All rights reserved.