pyrazolo[1,5-a]pyrazine

A four-step protocol for the synthesis of pyrazolo[1,5-a]pyrazines has been reported by Peter J. Lindsay-Scott and colleagues[1]. Commercially available pyrazoles were alkylated and formylated in a regiocontrolled manner to give pyrazole-5-aldehydes bearing 2,2-dialkoxyethyl substitution on N-1. Efficient conditions for the subsequent deprotection and cyclization of these intermediates allowed access to pyrazolo[1,5-a]pyrazines with multiple substitution patterns.

[1] A Flexible Strategy for the Regiocontrolled Synthesis of Pyrazolo[1,5-a]pyrazines. J. Org. Chem. 2017, 82, 20, 11295–11303. DOI: 10.1021/acs.joc.7b02128