Pentynol to furan conversion – Search for the best trans-[MX2(YNC10H14O)2] catalyst

Conversion of 4-pentyn-1-ol (A) into 2-methyl-2-pent-4-ynyloxy-tetrahydrofuran (B) is catalysed by camphorimine complexes trans-[PdCl2(YNC10H14O)2] (Y = NMe2, NHMe, NH2, OH, OMe, Pri, Ph), trans-[PdBr2(YNC10H14O)2] (Y = NMe2, NH2, OH, Ph), trans-[PtCl2(YNC10H14O)2] (Y = NMe2, NHMe, NH2). In the presence of H2O those catalysts further promote the conversion of 2-methyl-2-pent-4-ynyloxy-tetrahydrofuran (B) into 5-(2-methyl-tetrahydrofuran-2-yloxy)-pentan-2-one (C). The efficiency of each process highly depends on the characteristics of the Y group (at the camphor ligand), the halide (co-ligand) and the transition metal. To ascertain on the relevance of each parameter into the properties of the catalysts, the rate constants for A → B and B → C processes, TON, TOF and catalysts Activities (Ai) for A → B conversion were calculated. From the three sets of complexes studied the most efficient catalyst is trans-[PdCl2(H2NNC10H14O)2] while trans-[PdCl2(PhNC10H14O)2] is the less efficient. Palladium chloride are considerably better catalysts than palladium bromide complexes except in the case of trans-[PdBr2(HONC10H14O)2] that resembles chloride complexes efficiency. Compared to palladium, platinum complexes are considerably less efficient catalysts.