Benzyl esters of various acids can be chemoselectively cleaved on treatment with nickel boride in methanol at ambient temperature to give the parent carboxylic acids in high yields. Esters such as methyl, ethyl, tert-butyl, and trityl esters as well as benzyl ethers, tert-butyl ethers, and N-benzylamides remain unaffected under these conditions.
J. M. Khurana, R. Arora, Synthesis, 2009, 1127-1130.
A nickel boride catalyst prepared in situ from NiCl2 and sodium borohydride allowed facile reductions of a wide range of nitroarenes, aliphatic nitro compounds, and organic azides. Addition of modified nanocellulose enabled lower catalyst loading in nitro reductions. The protocols are compatible with a one-pot Boc-protection to provide the corresponding carbamates.
G. Proietti, K. J. Prathap, X. Yu, R. T. Olsson, P. Dinér, Synthesis, 2022, 54, 133-146.
A nickel boride catalyzed reduction of nitriles allows the preparation of Boc protected amines. The catalytic use of nickel(II) chloride in combination with excess sodium borohydride is environmental benign and tolerates air and moisture. Although the yield is sometimes moderate, the cleanliness of the method is exceptional.
S. Caddick, D. B. Judd, A. K. de K. Lewis, M. T. Reich, M. R. V. Williams, Tetrahedron, 2003, 59, 5417-5423.