The Synthesis of 3-pyrazinyl-pyrazolo [1,5-a] pyridines from an enol ether

Abstract The synthesis of 3-(6-chloropyrazin-2-yl)pyrazolo[1,5- a ]pyridine from an enol ether and 4-substituted 1-aminopyridinim iodides via a 3+2 cycloaddition is presented. A high throughput reaction screen was used to optimize the yield of the cycloaddition. This protocol is operationally simple, scalable, proceeds at room temperature, and the reaction profiles are very clean.