A Flexible Strategy for the Regiocontrolled Synthesis of Pyrazolo[1,5-a]pyrazines
Peter J. Lindsay-Scott*, Natalie G. Charlesworth and Alexandru Grozavu
*Eli Lilly and Company Limited, Erl Wood Manor, Windlesham, Surrey GU20 6PH, United Kingdom, Email: lindsay-scott_peterlilly.com
P. J. Lindsay-Scott, N. G. Charlesworth, A. Grozavu, J. Org. Chem., 2017, 82, 11295-11303.
DOI: 10.1021/acs.joc.7b02128 (free Supporting Information)
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Commercially available pyrazoles were alkylated and formylated in a regiocontrolled manner to give pyrazole-5-aldehydes bearing 2,2-dialkoxyethyl substitution on N-1. Subsequent deprotection and cyclization of these intermediates allowed access to pyrazolo[1,5-a]pyrazines with multiple substitution patterns, whereas a deprotection and double-reductive amination sequence provides 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazines.
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