Palladium-Catalyzed Dimerization Reactions Of Terminal Alkynes

The dimerization reaction of terminal alkynes is an important method for the synthesis of the conjugated enynes, conjugated diynes and conjugated dialkenes, and its products are useful building blocks in organic synthesis and are key units in a variety of biologically active compounds. The contents of this dissertation mainly reported the palladium-catalyzed dimerization reactions of terminal alkynes.1. PEG-400 (poly(ethylene glycol-400)) as a green reaction medium was found to promote the palladium-catalyzed dimerization reactions of terminal alkynes with elenctron-deficient alkynes. In the presentce of PdCl₂(PPh₃)₂, CuBr and PEG-400, treatment of terminal alkynes with elenctron-deficient alkynes afforded moderate to excellent yields The transformations could tolerate a range of functional groups. Noteworthy is that the reactions can be conducted under mild and environmentally benign conditions.2. DABCO (1,4-diaza-bicyclo[2.2.2]octane) as an efficient ligand could improve the palladium-catalyzed homocouplings of terminal alkynes. In the presence of Pd(OAc)₂, DABCO, Cul, NaOAc and air, the homocouplings of various terminal alkynes underwent smoothly to afford the corresponding diynes in moderate to excellent yields. Noteworthy is that the present reaction does not require expensive and instable phosphine ligands.