Photochemically-Mediated, Nickel-Catalyzed Synthesis of N-(Hetero)aryl Sulfamate Esters

Abstract

A general method is described for the coupling of (hetero)­aryl bromides with O-alkyl sulfamate esters. The protocol relies on catalytic amounts of nickel and photoexcitable iridium complexes and proceeds under visible light irradiation at ambient temperature. This technology engages a broad range of simple and complex O-alkyl sulfamate ester substrates under mild conditions. Furthermore, it is possible to avoid undesirable N-alkylation, which was found to plague palladium-based protocols for N-arylation of O-alkyl sulfamate esters. These investigations represent the first use of sulfamate esters as nucleophiles in transition metal-catalyzed C–N coupling processes.

Mapping Dual‐Base‐Enabled Nickel‐Catalyzed Aryl Amidations: Application in the Synthesis of 4‐Quinolones

“…The use of such bases is advantageous relative to strong inorganic bases (e.g., NaOtBu) that exhibit poor functional group tolerance, or weak inorganic bases (e.g., Cs 2 CO 3 ) that suffer from poor solubility and inconsistent reactivity profiles arising from particle size variation. [7] Notwithstanding the mechanistically innovative nature of these protocols, the substrate scope achieved by use of the above-cited [4][5][6] and other related photoredox/ electrochemical/reductant methods [8] is typically limited to electronically activated (hetero)aryl bromides paired with alkylamine, aniline, or sulfur-based (e.g., sulfonamide, [9] sulfamide, [10] sulfamate ester, [11] sulfoximine [12] ) nucleophiles. Absent from such reports is the general application of (hetero)aryl chloride or phenol derivatives, which represent the most attractive electrophile classes owing to their low cost and wide availability.…”

Nickel‐Catalyzed Cross‐Coupling of Sulfonamides With (Hetero)aryl Chlorides

“…A similar protocol was used subsequently by Roizen and co-workers in the Narylation of sulfamate esters. [14] We have adopted a complementary "photoredox-free" approach that exploits ancillary ligand design [15] as a means of enabling Ni-catalyzed CÀN and related cross-couplings, particularly involving (hetero)aryl chlorides and phenol derivatives for which photoredox-promoted methods are generally ineffective. One aspect of this research involves the development and/or application of sterically demanding and modestly electron-donating bisphosphines [16] (including the DalPhos series, Figure 1 C [17] ), which we envisioned might promote CÀN reductive elimination within a putative Ni(0/II) catalytic cycle, [18] while circumventing catalyst deactivation arising from bis-chelation and/or comproportionation.…”

Nickel‐Catalyzed Cross‐Coupling of Sulfonamides With (Hetero)aryl Chlorides

“…Such an approach is employed in the only report of Ni‐catalyzed sulfonamide N ‐arylation chemistry (Figure B), whereby (glyme)NiCl 2 (5 mol %) in the presence of an Ir photocatalyst (in some cases with 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine, dtbbpy) enabled the C−N cross‐coupling of primary sulfonamides with (hetero)aryl bromides. A similar protocol was used subsequently by Roizen and co‐workers in the N ‐arylation of sulfamate esters …”