Process of preparing a pd-1/pd-l1 inhibitor

A process of preparing (R)-1-((7-cyano-2-(3′-((3-(((R)-3-hydroxypyrrolidin-1-yl)methyl)-1,7-naphthyridin-8-yl)amino)-2,2′-dimethyl-[1,1′-biphenyl]-3-yl)benzo[d]oxazol-5-yl)methyl)pyrrolidine-3-carboxylic acid, or a salt thereof, comprising:

• reacting a compound of formula III-5:
• or a salt thereof, with a compound of formula IV-1:
• or a salt thereof, in the presence of a Suzuki catalyst and a base to form a compound of formula IV-2:
• or a salt thereof, wherein:
• each R3 is independently selected from H and C1-6 alkyl;
• or
• each R3 together form an C2-3 alkylene linker, which is optionally substituted by 1, 2, 3, or 4 independently selected C1-4 alkyl groups;
• and
• R4 is C1-6 alkyl;
• and
• X1 is halo.