Decarboxylative Cross-Electrophile Coupling of N-Hydroxyphthalimide Esters with Aryl Iodides

Abstract

A new method for the decarboxylative coupling of alkyl N-hydroxyphthalimide esters (NHP esters) with aryl iodides is presented. In contrast to previous studies that form alkyl radicals from carboxylic acid derivatives, no photocatalyst, light, or arylmetal reagent is needed, only nickel and a reducing agent (Zn). Methyl, primary, and secondary alkyl groups can all be coupled in good yield (77% ave yield). One coupling with an acid chloride is also presented. Stoichiometric reactions of (dtbbpy)Ni(2-tolyl)I with an NHP ester show for the first time that arylnickel(II) complexes can directly react with NHP esters to form alkylated arenes.

Photoredox Catalysis in Organic Chemistry

“…Indeed, the Baran and Weix laboratories have recently developed elegant variants using Okada’s redox-active esters in combination with organozinc nucleophiles. 109 In addition to carboxylic acids, we have shown that α-amino C–H bonds of N -arylamines can be used as handles for cross-coupling in the outlined photoredox Ni catalysis methodology. Here, α-amino radicals are generated via an oxidation–deprotonation sequence (see Scheme 5).…”

Well-defined nickel and palladium precatalysts for cross-coupling

“…Recently, [(dtbbpy)NiBr 2 ] was used by the group of Weix 131 to facilitate cross-electrophile couplings of aryl and alkyl halides in the presence of the organic reductant tetrakis(dimethylamino)ethane in non-amide solvents. Alternatively, the same group demonstrated 132 that a non-photoredox- initiated decarboxylative coupling between aryl iodides and N -hydroxyphthalimide ester electrophiles could be catalysed by [(dtbbpy)NiBr 2 ] over elemental Zn. The precedent for this chemistry lies, in part, in reports describing the electrochemical synthesis of ketones from alkyl and aryl electrophiles using [(bpy)NiBr 2 ] or [(bpy) 3 Ni](BF 4 ) 2 (bpy = 2,2′-bipyridine) 133,134 .…”

A general alkyl-alkyl cross-coupling enabled by redox-active esters and alkylzinc reagents

“…(21, 22) Certain active esters (e.g. HOAt (aza – N -hydroxybenzotriazole), HOBt ( N -hydroxybenzotriazole), NHPI ( N -hydroxyphathalimide) TCNHPI (tetrachloro N -hydroxyphthalimide)) can accept an electron to trigger an ensuing cascade of events that liberates CO2 from the parent alkyl group (Alk1); such esters (23) are termed redox-active.…”