Carboxylic Acid Directed C-H Arylation of Azulene

Org Lett. 2020 Jul 2;22(13):5009-5013. doi: 10.1021/acs.orglett.0c01576. Epub 2020 Jun 17.

Abstract

The first example of directed C-H activation for azulene is reported. A variety of 2-arylazulenes are obtainable exclusively from 1-azulene carboxylic acids, with yields of up to 82%. Some heteroaryl groups such as pyridine and thiophene are also tolerated in the reaction. The efficacy of the reaction is found to be highly dependent on the conditions, with a phosphate base and a bulky carboxylic acid being key additives.