Ni(II)/Al(0) mediated benzylic $$\hbox {Csp}^{3}$$-$$\hbox {Csp}^{3}$$ coupling in aqueous media

Abstract

The reaction of benzyl bromides and chlorides with aluminium metal powder or foil (1.2 eqv.) in the presence of catalytic nickel nitrate (10 mol%) in water at room temperature resulted in homocoupling to the corresponding bibenzyl products which were isolated in moderate to good yields. In sharp contrast, the same reaction in organic solvents like dichloromethane, dimethylformamide, acetonitrile, methanol and toluene yielded only a trace amount of the desired product. The scope of the reaction was tested with substituents on the aromatic ring such as Me-, Cl-, CN-, F-, NO 2-, Ph-as well as 2 • benzyl halides.

Homocoupling of benzyl pyridyl ethers via visible light-mediated deoxygenation

“…Bibenzyls are important motifs found in many biologically active natural products and drugs, making their efficient synthesis crucial for pharmaceutical research and development (Scheme 1). [1][2][3][4][5] Traditionally, these compounds have been synthesized via transition-metal-catalyzed C(sp 3 )-C(sp 3 ) homocoupling reactions 6 of benzyl halides, [7][8][9][10][11][12][13][14][15][16] Grignard reagents, [17][18][19] or organozinc reagents (Scheme 2a). 20 More recently, visible-light photoredox catalysis has emerged as a mild and effective alternative for bibenzyl synthesis through photoinduced reductive cleavage (Scheme 2b).…”