A highly regioselective Mg-catalyzed alkylation of 3-substituted pyrazoles has been developed to provide N2-alkylated regioisomers. Using α-bromoacetates and acetamides as alkylating agents, this new method was applied to a variety of 3-substituted and 3,4-disubstituted pyrazoles to produce the N2-alkylated products with high regioselectivities ranging from 76:24 to 99:1 and 44–90% yields.
Compounds of Formula (I)
wherein R
1
, R
2
, R
3
, R
4
and R
5
are defined herein, maintain good activity against NS3 proteases containing clinically relevant genotype 1a R155K and genotype 1b D168V resistance mutations. The compounds are useful as inhibitors of HCV NS3 protease for the treatment of hepatitis C viral infection.