Nickel-Catalyzed Decarboxylative Alkylation of Aryl Iodides with Anhydrides

Abstract

We present the anhydride-based decarboxylative alkylation of aryl iodides catalyzed by nickel. This method of decarboxylative coupling works with a broad scope of aliphatic carboxylic anhydrides and tolerates synthetically useful aromatic substituents. Assisted by a redox system of pyridine N-oxide and zinc additives, the current reaction occurs under mild conditions and without the assistance of photocatalyst. Notably, this method features high chemoselectivity toward alkyl migration with mixed aliphatic/aromatic anhydrides. Thus, it provides a powerful synthetic tool to modify high-valued aliphatic carboxylic acids by converting them into mixed anhydrides using readily available aryl carboxylic acids such as p-toluic acid. We propose a catalytic cycle that involves the key steps of free radical-based decarboxylation and subsequent alkyl transfer to nickel that precedes an oxidatively induced C–C reductive elimination from Ni­(III).

Nickel-catalyzed C–N bond activation: activated primary amines as alkylating reagents in reductive cross-coupling

“…Traditionally, alkyl halides,3 which may have limited stability and availability, have been used as alkyl electrophiles. Recently, N -hydroxyphthalimide esters, anhydrides, benzyl oxalates, tosylates and mesylates have been reported as alkyl coupling partners 4. However, the use of primary amines as readily available, cheap, green and stable alkylating reagents in reductive cross-coupling has not been described.…”

Regio- and Stereoselective Rhodium(II)-Catalyzed C–H Functionalization of Cyclobutanes

“…This study began by surveying dirhodium tetracarboxylate catalysts for functionalizing readily available cyclobutane 6 (Figure 3). 37 The reactions were conducted in refluxing methylene chloride with 2,2,2-trichloroethyl 2-(4-bromophenyl)-2-diazoacetate (7) 38 as the carbene precursor. The use of 2,2,2-trihaloethyl ester groups is often advantageous in the dirhodium-catalyzed reactions of donor and acceptor carbenes because they can enhance enantioselectivity.…”

Recent Progress in Radical Decarboxylative Functionalizations Enabled by Transition-Metal (Ni, Cu, Fe, Co or Cr) Catalysis

“…Moreover, high chemoselectivity of alkyl-over aryl-migration was observed when alkyl/aryl unsymmetrical acid anhydrides were used (Scheme 12). 14 The substrate scope of the reactions can be further expanded to complex molecules, natural products and drug molecules via the formation of mixed anhydrides with 4-toluic acid (Scheme 12).…”

“…We proposed a possible mechanism (Scheme 13), 14 where we believed that Ni II is reduced by Zn to form complex 13.1, to which oxidative addition of the aryl iodide results in aryl-Ni II complex 13.2. The complex 13.2 is then reduced to Ni I species 13.3 which delivers an electron through SET to active ester 13.4 to form Ni II complex 13.6.…”