Improved Synthesis of the Nav1.7 Inhibitor GDC-0276 via a Highly Regioselective S_NAr Reaction

The development of a redesigned and improved second-generation synthesis of the Nav1.7 inhibitor GDC-0276 based on experience gained from a fit-for-purpose first-generation synthesis will be described. The first-generation synthesis proceeded via a regioselective S_NAr reaction on the advanced starting material t-butyl 5-chloro-2,4-difluorobenzoate with 1-adamantanemethanol. In the newly developed second-generation synthesis, the much improved regioselective S_NAr reaction was performed on the readily available starting material 1-chloro-2,4-difluorobenzene, followed by installation of the carboxylate group by electrophilic aromatic bromination and a palladium-catalyzed alkoxycarbonylation. A subsequent Suzuki–Miyaura cross-coupling reaction was then telescoped directly into a phase-transfer-catalyzed ester hydrolysis. Amidation of the resulting acid intermediate with 1-azetidine sulfamide in turn provided GDC-0276 in high overall yield and purity on a 100 kg scale.