Co^I‐Catalyzed Barbier Reactions of Aromatic Halides with Aromatic Aldehydes and Imines

Abstract

The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr2/1,10‐phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro‐nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.

Effects of Ionic Liquids on the Nucleofugality of Chloride

“…The product was recrystallized from hexane as white crystals (0.410 g, 1.91 mmol, 42%). Mp 51–53 °C (lit . 52–53 °C).…”

“…Mp 51−53 °C (lit. 67 4-Bromobenzhydrol. 68 4-Bromobenzophenone (1.50 g, 5.70 mmol) and sodium borohydride (0.327 g, 8.60 mmol) were used.…”

Recent advances in the synthesis of xanthones and azaxanthones

“…However, the presence of a carboxylic acid derivative is not mandatory, and other substrates such as 2-iodo diaryl ethers (Y = I) or the corresponding diazonium salts (Y = N 2 + BF 4 − ) can be used for the synthesis of xanthones in a palladium-catalysed carbonylation/C-H activation (section 4.1.2.5). Other kinds of cyclization strategies have also been reported in which the xanthone core can be obtained through a Co(I)-catalysed Barbier reaction of aromatic halides with aromatic aldehydes and imines, 156 a PhI(OAc) 2 -BF 3 -OEt 2 mediated domino imine activation, intramolecular C-C bond formation and β-elimination, 157 or a quaternary ammonium salt-promoted intramolecular dehydrogenative arylation of aldehydes. 158 4.1.2.1 Cyclization of diaryl ethers to xanthones by a crossdehydrogenative coupling.…”

Nickel-catalyzed reductive coupling of unactivated alkyl bromides and aliphatic aldehydes

“…[6][7][8] Net reductive couplings using organohalide feedstocks have been developed using stoichiometric reductants to enable catalyst turnover, obviating the need for pre-generation of the organometallic nucleophile. [9][10][11][12][13][14][15][16] Among the most common systems are Rh 10 , Ni 11,[14][15][16] and Cr [17][18][19][20][21][22][23][24] -catalyzed couplings of aldehydes and organohalides. Importantly, each of these systems are proposed to proceed via Grignard-type mechanisms, generating organometallic nucleophiles that undergo formal additions to carbonyl electrophiles.…”