Copper-catalyzed decarboxylative

A synthesis of benzotriquinacene 396) has recently been described (Scheme 63).36s 366 Vinylmagnesium chloride transformed ketone 380 into vinyl alcohol 393 whose dehydration gave 2-vinyltriquinacene 394). Addition of dimethyl acet-ylenedicarboxylate to 394 followed by dehydrogenation led to adduct 395 which underwent ready saponification and copper-catalyzed decarboxylation to give 396. 

Since then, experiments have been reported which indicate that (1) organocopper compounds will couple with aryl halides (2) arylcopper compounds can be oxidatively and thermally dimerized (3) arylcopper compounds are intermediates in the Ullmann reaction (4) organocopper compounds are intermediates in copper-catalyzed decarboxylations and (5) copper-promoted coupling reactions are not restricted to aromatic halides. The copper(I) oxide-promoted coupling reactions, however, have still to yield firm evidence of a copper intermediate. 

Decarbonylation decarboxylation. At 110-170° this complex in catalytic amounts effects decarbonylation of simple aldehydes in quantitative yield.2 Decarbonylation of typical indole-2-carboxaldehydes with in s/ta-generated catalyst proceeds in 82-95% yield. In fact, decarboxylation of some indole-2-carboxylic acids can be effected in higher overall yield by conversion to the aldehyde (LiAlH4 Mn02) followed by decarbonylation than by copper-catalyzed decarboxylation.3... 

GooBen LJ, Zimmermann B, Knauber T (2008) Palladium/copper-catalyzed decarboxylative cross-coupling of aryl chlorides with potassium carboxylates. Angew Chem Int Ed 47 7103-7106... 

Nilsson, M. A new blaryl synthesis Illustrating a connection between the Ullmann blaryl synthesis and copper-catalyzed decarboxylation. Acta Chem. Scand. 1966, 20, 423-426. 

A novel copper-catalyzed decarboxylative arylation of a variety of benzoxazoles with 2-nitrocarboxyhc acids (218) was reported to be most effective with electron-rich benzoxazoles by Hoover and coworkers (2015CC15059). Moreover, the presence of the ortho-nitro group was found to be essential for coupling, suggesting that this group plays a role in faciH-tating the decarboxylation step. 

Shang, R., Fu, Y., Wang, Y., Xu, Q., Yu, H.-Z., Liu, L. (2009). Copper-catalyzed decarboxylative crosscoupling of potassium polyfluorobenzoates with aryl iodides and bromides. Angewandte Chemie International Edition, 48, 9350-9354. 

In 2010, Xue and coworkers [41] reported the viability of a copper-catalyzed decarboxylative coupling of alkynyl carboxylic acids with aryl h llides under relatively mild reaction conditions (Scheme 3.24a). On the basis of computation2il investigations, the authors proposed that in the initial step of the catalytic cycle, the copper(I) precursor was oxidized to a copper(lll) complex. 

Scheme 3.23 Copper-catalyzed decarboxylative cross-coupling of potassium polyfluorobenzoates with aryl halides, as described by Liu and coworkers [40].

The copper-catalyzed decarboxylative coupling of cinnamic acids with benzylic hydrocarbons through sp C-H bond cleavage can proceed by a radical mechanism (Scheme 4.60) [61]. 

The copper-catalyzed arylation of propiolic acids was disclosed by You s (Scheme 4.65) [66] and Jiao s groups [67] independently. The latter group also reported the copper-catalyzed decarboxylative amidation of propiolic acids to produce the corresponding amides (Scheme 4.66) [68]. 

The copper-catalyzed decarboxylative coupling of a-keto carboxylic acids with indoles can proceed through C-H bond cleavage at their C3-position (Scheme 4.76) [78]. In contrast, the coupling with Ar-(pyrimidin-2-yl)indoles occurs at their C2-position under palladium catalysis [79]. 

SCHEME 4.337 Copper-catalyzed decarboxylative synthesis of vinylphosphonates and... 

The copper-catalyzed decarboxylative phosphonylation of carboxylic acids has been achieved [482]... 

Feng Q, Song Q (2014) Copper-catalyzed decarboxylative C=N triple bond ftmtiation direct synthesis of benzonitriles from phenylacetic acids under O2 atmosphere. Adv Synth Catal 356(8) 1697-1702... 

Ranjit S, Duan Z, Zhang P, Liu, X. Synthesis of vinyl sulfides by copper-catalyzed decarboxylative C—S cross-coupling. Org. Lett. 2010 12 4134- 136. 

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