Discovery of A Novel Palladium Catalyst for the Preparation of Enynes with a Copper- and Ligand-Free Sonogashira Reaction

• Published in: Synlett 2012-05, Vol.2012 (8), p.1257-1261
• Main Authors: Mi, Xia, Huang, Mengmeng, Feng, Yujian, Wu, Yangjie
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; letter; Noncondensed benzenic compounds; Organic chemistry; Preparations and properties; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0936-5214; 1437-2096
• DOI: 10.1055/s-0031-1290938

Abstract A new palladium(II) complex based on N , N -dimethylethanolamine, ( SP -4-1′)-bis[ N , N -dimethylaminoethoxy-k N , O ]palladium(II) which coordinates with two moles of AcOH, has been synthesized. The structure of the complex has been established by X-ray diffraction analysis. Using this complex as a catalyst, a series of conjugated enynes were successfully synthesized by Sonogashira cross-coupling reaction in the absence of co-catalyst CuX and any ligand at room temperature during 20 hours affording the corresponding products in moderate to excellent yields. The optimized catalytic systems are tolerant in the presence of a broad variety of functional groups in the substrates. The catalytic system was found to be ineffective for vinyl chloride. Moreover, it was found that ( Z )-β-bromostyrene reacts with terminal alkynes with retention of the steric configuration and the transformation of most of the Z -isomer did not occur in this reaction.