Synthesis of Air‐stable, Odorless Thiophenol Surrogates via Ni‐Catalyzed C−S Cross‐Coupling

Thiophenols are versatile synthetic intermediates whose practical appeal is marred by their air sensitivity, toxicity and extreme malodor. Herein we report an efficient catalytic method for the preparation of S‐aryl isothiouronium salts, and demonstrate that these air‐stable, odorless solids serve as user‐friendly sources of thiophenols in synthesis. Diverse isothiouronium salts featuring synthetically useful functionality are readily accessible by nickel‐catalyzed C−S cross‐coupling of (hetero)aryl iodides and thiourea. Convenient, chromatography‐free isolation of these salts is achieved by precipitation, allowing the methodology to be applied directly to large scales. Thiophenols are liberated from the corresponding isothiouronium salts upon treatment with a weak base, enabling an in situ release/S‐functionalization strategy that entirely negates the need to isolate, purify or manipulate these noxious reagents. Coming up roses: Ni‐catalyzed cross‐coupling provides access to S‐aryl isothiouronium salts under mild conditions. These air‐stable, odorless solids are isolated without chromatography, and are convenient sources of thiophenols in synthesis. The scope and utility of the methodology is illustrated with 60 examples and is showcased through the concise synthesis of celecoxib.