Metal-free Hydroalkoxylation-Formal [4+2] Cycloaddition Cascade for the Synthesis of Ketals
作者:Santosh J. Gharpure、Santosh K. Nanda、Padmaja、Yogesh G. Shelke
DOI:10.1002/chem.201701659
日期:2017.7.26
A transition metalfree, acid promoted cascade hydroalkoxylation–formal [4+2] cycloaddition of various alkynols with salicylaldehyde is demonstrated for the synthesis of tetrahydrofurano/pyrano‐chromenes and spiroketals. In general, alkynols underwent hydroalkoxylations in an endo‐dig manner when internal alkynes were used to furnish the heteroannular ketals, whereas terminal alkynes proceeded in an