Highly efficient and tunable synthesis of dioxabicyclo[4.2.1] ketals and tetrahydropyrans via gold-catalyzed cycloisomerization of 2-alkynyl-1,5-diols.
A highly efficient gold(I) chloride catalyzed cycloisomerization of 2-alkynyl-1,5-diol (1) to dioxabicyclo[4.2.1] ketal (2) and its further transformation to tetrahydropyran (3) are reported. The diol is readily obtained by the reduction of 2-alkynyl-substituted glutarates, isolated from the Michael addition of allenoates to methyl acrylate. These reactions proceeded smoothly under very mild conditions. A plausible mechanism for the formation of the said tetrahydropyran from the corresponding ketal is proposed.
Liu
Le-Ping
LP
Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA. leping.liu@louisville.edu
Hammond
Gerald B
GB