Rieke Ni generated in situ was able to promote the pinacol coupling of various carbonyls efficiently. Another catalytically effective, cheaper and more convenient NiCl2(Cat.)/Mg/TMSCl system was designed and developed further successfully. Single-electron transfer (SET) mechanisms for the coupling reactions and the DL/meso diastereoselectivity were also explained.
L. Shi, C.-A. Fan, Y.-Q. Tu, M. Wang, F.-M. Zhang, Tetrahedron, 2004, 60, 2851-2855.
Exposure of (functionalized) aryl chlorides to catalytic quantities of nickel-on-charcoal in the presence of stoichiometric amounts of Me2NH · BH3/K2CO3 in refluxing acetonitrile leads to high yields of the dehalogenated arenes.
B. H. Lipshutz, T. Tomioka, K. Sato, Synlett, 2001, 970-973.
Nickel-on-graphite is a very inexpensive, heterogeneous catalyst for the chemoselective reduction of aryl tosylates and mesylates. The catalyst can be used under conventional heating conditions or microwave irradiation and is recyclable without loss of activity.
B. H. Lipshutz, B. A. Frieman, T. Butler, V. Kogan, Angew. Chem. Int. Ed., 2006, 45, 800-803.
A system composed of nickel(II) chloride, lithium metal, a catalytic polymer-supported arene, and ethanol, has been efficiently applied to the conjugate reduction of various α,β-unsaturated carbonyl compounds under very mild reaction conditions.
F. Alonso, I. Osante, M. Yus, Synlett, 2006, 3017-3020.
The reaction of 1-(methylthio)acetone with different nitriles in the presence of triflic anhydride gave 2-substituted 5-methyl-4-methylthio-1,3-oxazoles in good yield. The methylthio group at the C4 position can easily be removed with Raney nickel. 4-Methylsulfonyl derivatives were prepared by the oxidation of the MeS group with m-CPBA.
A. Herrera, R. Martinez-Alvarez, P. Ramiro, D. Molero, J. Almy, J. Org. Chem., 2006, 71, 3026-3032.
A directing-group-enabled regioselective Ir-catalyzed (3+2) cycloaddition of azides and alkynes provides functionalized triazoles under mild conditions. The triazene directing group can be replaced by diverse groups, including amino, amide, halogen, and heterocycle substituents.
L. Zeng, Z. Lai, C. Zhang, H. Xie, S. Cui, Org. Lett., 2020, 22, 2220-2224.