1207863-91-9Relevant articles and documents
Nickel complexes of nio-functionalized n-Heterocyclic carbenes as precatalysts for michael reactions in air at room temperature under the much preferred base-Free conditions
Ray, Sriparna,Shaikh, Mobin M.,Ghosh, Prasenjit
experimental part, p. 1932 - 1941 (2009/10/30)
A series of several new nickel precatalysts supported over N/O-functionalized N-heterocyclic carbenes (NHC) for the Michael reactions of B-dicarbonyl, B-keto ester, B-diester, and a-cyano ester compounds with a,B-unsaturated carbonyl compounds in air at ambient temperature under the much preferred base-free conditions are reported. Specifically, the nickel complexes, [1-(R1-aminocarbonylmethyl)-3-R2-imid-azol-2-ylidene]2Ni [R1 =2-C6H4(OMe); R2 = Me (1b), iPr (2b), CH2Ph (3b) and R1 = 2-CH2C4H3O; R2 =Me (4b), CH2Ph (5b)] carried out the highly convenient base-free Michael addition of the activated C-H compounds across a,B-unsaturated car- bonyl compounds in air at room temperature. The complexes 1b-5b were synthesized by the direct reaction of the respective imidazolium chloride salt with NiCl2-6H2Oin CH3CN in the presence of K2CO3 as a base. The exceptional stability of 1b-5b has been attributed to the deeply buried nickel-NHC CT-bonding molecular orbitals as evidenced from the density functional theory (DFT) studies. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009.
