Nickel-catalyzed decarboxylation

In 2012, Yamaguchi, Itami, and coworkers [43] reported the first nickel-catalyzed decarboxylation C-H biaryl coupling of azoles with aryl esters. No stoichiometric oxidants or expensive catalysts were needed to perform this reaction. This methodology was successfully applied for the convergent formal synthesis of Muscoride A (a natural product with antibacterial activity) (Scheme 3.26). The flexibility of this approach will likely enable the preparation of a series of analogs of the Muscoride family [44]. 

Scheme 3.26 Application of nickel-catalyzed decarboxylative C-H coupling in the formal synthesis of Muscoride A, as described by Yamaguchi, Itami, and coworkers [43, 44].

Yoshino Y, Kurahashi T, Matsubara S. Nickel-catalyzed decarboxylative carboamination of alkynes with isatoic anhydrides. J. Am. Chem. Soc. 2009 131(22) 7494-7495. 

Matsubara and coworkers have recently developed a nickel-catalyzed cycloaddition of isatoic anhydrides with alkynes to afford 2,3-disubstituted indoles in good yields (Scheme 22.16). The cycloaddition reaction proceeds via a decarbonylation, decarboxylation, and alkyne insertion sequence [24]. 

Nakai, K., Kurahashi, X, Matsubara, S. (2013). Nickel-catalyzed decarbonylative and decarboxylative cycloaddition of isatoic anhydrides with alkynes. Chemistry Letters, 42, 1238-1240. 

The cadmium secocorrinoid carboxylic acid (102 M = Cd) also undergoes photocyclization to the acid (103 M = Cd), which on transmetallation to the nickel(II) complex (103 M = Ni) and treatment with triethylamine and acetic acid yields the parent corrin complex (100 M = Ni).268 The decarboxylation process is extremely facile. A related base-catalyzed cyclization of the secocorrinoid aldehyde (104) gives the corrin complex (105), which can be decarbonylated to the parent complex (100 M = Ni) by treatment with potassium hydroxide (Scheme 66).268... 

Transition metal-catalyzed cross-coupling reactions of halogenopyrazines is an efficient synthetic method for alkyl-, alkenyl-, and alkynylpyrazines (Section 6.03.5.4.2). Palladium and nickel complexes are particularly effective as catalysts in this reaction. The Wittig reaction of halogenomethyl-pyrazines likewise leads to the formation of alkenylpyrazines (Section 6.03.8.1). Dehalogenation of halogeno pyrazines is a very practical synthetic method for alkyl- or aryl-substituted pyrazines. For example, phenylpyrazine has been prepared by catalytic hydrogenolysis of the 2-chloro-3-phenyl compound in the presence of triethylamine. This product is also obtained by decarboxylation of... 

Phenols have been condensed with alkenoylesters to give chromans by an oxa-Michael addition/electrophilic aromatic addition sequence with magnesium(II)- or copper(II)-bis-oxazoline complexes as chiral Lewis acid catalysts (Scheme 17b) [97]. This reaction may be initiated by an oxa-Michael reaction, followed by a hydroarylation of a carbonyl group. The authors suggest that the initial stereodetermining oxa-Michael addition is followed by a fast diastereoselective aromatic substimtion [97]. A nickel Lewis acid, derived from Ni(hfacac)2 (hfacac = 1,LL5,5,5-hexafluoro-3,5-dioxopentane enolate) and chiral Al-oxide ligands, catalyzes the enantioselective oxa-Michael cyclization of 2-tert-butyloxycarbonyl-2 -hydroxy-chalcones to 3-ferf-butoxycarbonyl flavanones, which can be decarboxylated to flavanons in a separate step (Scheme 17c) [98]. A Lewis acid activation of the unsaturated p-ketoester unit can be assumed. 

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