Cooperative effect of the camphor imine ligand in alkynols activation by trans-[MCl2(YNC10H14O)2] (M = Pd or Pt)

The cooperative effect of the camphor imine ligand (YNC10H14O) in the cyclization of 5-hexyn-1-ol and 4-pentyn-1-ol promoted by complexes trans-[MCl2(YNC10H14O)2] (M = Pd, Y = NH2, NHMe, NMe2, OH, Ph; Pt, Y = NH2, NHMe, NMe2) is established from a direct relation between the constants calculated for conversion of 5-hexyn-1-ol (A) into 2-methyl-2-pent-4-ynyloxy-tetrahydropyran (B) and 4-pentyn-1-ol (C) into 2-methyl-2-pent-4-ynyloxy-tetrahydrofuran (D) and the basic character of the camphor imine substituent (Y). In the catalytic process acid–base interactions between the alkynol and the coordinated camphor imine are supported by the structural characterization of [PdCl4][Me2NHNC10H14O]2.

Graphical abstractFormation of [PdCl4][Me2HNNC10H14O)2]·2CHCl3 by reaction of trans-[MCl2(YNC10H14O)2] complexes with acid gives a clue on the mechanism of alkynols cyclization.Figure optionsDownload full-size imageDownload as PowerPoint slide