Synthesis toward CRHR1 Antagonists through 2,7-Dimethylpyrazolo[1,5-α][1,3,5]triazin-4(3<i>H</i>)-one C–H Arylation

Abstract

A novel synthetic protocol for 8-aryl substituted pyrazolo[1,5-α][1,3,5]triazin-4(3H)-ones was developed employing Pd-catalyzed C-H arylation. The reaction yield was influenced by the presence of a phosphine ligand, pivalic acid, and base selection. With the use of 5-10 mol % catalyst, reactions of 2 with p- or m-substituted aryl bromides proceeded in moderate to good yields. Lower yields were observed with o-substituted aryl bromides. Using this method a precursor for MJL1-109-2, a known nonpeptide CRHR-1 antagonist, was successfully synthesized.