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

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.