Nitrate Reduction for Deaminative Suzuki-Miyaura Coupling of Anilines

Abstract

We present a deaminative Suzuki-Miyaura-type coupling (SMC) of anilines with nitrate as a diazotization reagent, which integrates transition-metal catalysis with nitrate-based diazonium chemistry for the first time. The synergistic reduction of nitrate by bisulfite and boronic acids allows for both oxidative diazotization with low-valent transition metal redox transformations simultaneously. The reaction utilizes low-hazard, readily available starting materials and reagents. In comparison to previous diazonium-based Suzuki-Miyaura-couplings, the in situ oxidation of anilines by reduction of nitrate allows larger functional group tolerance.

Keywords: Aniline; Cross coupling; Nitrate; Suzuki–Miyaura coupling.

Scheme 1

Design of SMC reaction of anilines with nitrate reduction strategy.

Scheme 2

Reaction condition investigation. ^a Yields were determined by ¹⁹F NMR using α,α,α‐trifluorotoluene as internal the standard.

Scheme 3

Substrate scope. ^a Pd(OAc)₂ 2.5 mol %, L1 5 mol % was used.

Scheme 4

Control experiments and proposed mechanism. NO₂ was observed by obtaining brown gas formation and further detected by UV–vis spectroscopy (Figure S6).