Electrosynthesis of symmetrical ketones from organic halides and carbon dioxide catalysed by 2,2′-bipyridine-nickel complexes

Carbon−Carbon Bond Formation with Electrogenerated Nickel and Palladium Complexes

“…[Ni(CO) 2 (bipy)] was formed from an electroreduction process of CO 2 to CO. [112] The addition of benzyl chloride, or of an alkyl bromide or iodide, to the system resulted in the formation of a symmetrical ketone, RCOR, in yields of 60Ϫ85%. [113] The electroreduction of [PdCl 2 (PPh 3 ) 2 ] in the presence of carbon monoxide allowed the formation of lowly ligated [Pd(CO)(PPh 3 ) 2 ].…”

Nickel Bromide Bipyridine

“…The electrosynthesis of symmetrical ketone has also been achieved reducing NiBr 2 bipy on a magnesium rod in a DMF or NMP solution saturated with CO 2 . 10 The reduction of both the Ni II and CO 2 first affords the Ni 0 bipy(CO) 2 complex that undergoes an oxidative addition on RX (R = Alk, Ar) followed by an internal CO shift and reductive elimination (eqs 4-9).…”

“…A second oxidative addition of RX leads to a Ni III species that undergoes a reductive elimination, generating a Ni I bipy (that is in turn reduced in Ni 0 bipy) plus the dimer (biaryl or dienic products). Note that this mechanism does not apply to o-substituted aryl derivatives since the corresponding ArNiXbipy are more stable (they can even be isolated in some cases 1/2 NiX 2 bipy + 1/2 R 2 Nibipy 1/2 R-R + 1/2 Ni 0 bipy (10) The stereoselectivity associated with the vinyl couplings depends on the configuration of the original double bond 20 : while (E)-vinyl substrates provide the (E,E)-dienes, the (Z)-ones lead to a mixture of (Z,Z)-and (Z,E)-dienes in ratios going from 70:30 to 60:40.…”

Carbonylation and Decarbonylation

“…Method B: Utilization of CO 2 as a CO Source [16] Ni(bpy)Br 2 (0.6 mmol), Bpy (0.9 mmol), NMP (30 mL), CO 2 saturation, Bu 4 NBF 4 (3 mmol), 10 Â (À1.6 V versus SCE), RX (10 Â 0:6 mmol).…”

“…An active species 8.15 undergoes oxidative addition upon RX and forms 8. 16, which disproportionates to give 8.17 and 8. 19.…”