An in Situ Approach for Nickel-Catalyzed Cycloaddition

Abstract

A convenient method for preparing pyridines from air-stable, commercially available catalyst precursors is described. The addition of n-BuLi to Ni(acac)2 and an NHC salt (such as IPr.HCl or SIPr.HCl) rapidly generates an active Ni0/NHC catalyst for the cycloaddition of diynes and nitriles that affords pyridines without a decrease in observed yields. The in situ method also converts diynes and carbon dioxide to the corresponding pyrones.

Cationic Rhodium(I)/H8‐binap Complex Catalyzed [2+2+2] Cycloadditions of 1,6‐ and 1,7‐Diynes with Carbonyl Compounds

“…Starting Materials: Diynes 1a, [32] 1b, [11c] 1c, [25g] 1d, [33] 1e, [32] 1g, [34] 1i, [35] 1j, [35] and 1k [3] and carbonyl compounds 2e, [36] 8c, [37] 8e, [38] and 8f [18] were prepared according to literature procedures. Anhydrous CH 2 …”

[NiX2(NHC)2] Complexes in the Hydrosilylation of Internal Alkynes

“…[26] As a reducing agent butyllithium was considered, although it was unclear whether this reagent could be used to activate nickel(II) complexes, rather than nickel(II) salts. [27][28][29] In addition, triethylaluminium, diethylzinc and phenylmagnesium chloride were evaluated. Trialkylaluminium compounds are known for the activation of Ni(acac) 2 in Zieglertype catalysts, the zinc reagent is anticipated to have similar alkylating properties, [30] and the Grignard reagent is used for the activation of nickel dihalide complexes in the Kumada coupling reaction.…”

Nickel‐Catalyzed [2+2+2] Cycloaddition of Diynes and Cyanamides

“…[45] The method employed [Ni(acac) 2 ] as a nickel source, an appropriate NHC·HCl or HBF 4 salt, and n BuLi as a simultaneous reductant and base. We found this in situ method was also effective for the [2+2+2] cycloaddition reactions of diynes and cyanamides.…”