Chemoselective O‐Benzylation of the Propargylic Hydroxy Group in Polyols

Abstract

We have discovered the highly chemoselective benzylation of propargylic hydroxy groups in the presence of other hydroxy groups under very usual conditions involving benzyl bromide and sodium hydroxide in DMF at room temperature. This methodology has a high synthetic utility for the selective protection of hydroxy groups at the propargylic position among various other hydroxy groups in complex molecules.

Ring-Closing Metathesis Reactions of Bis(enynes): Selectivity and Surprises

“…This final step was hindered by formation of a rearrangement byproduct 8 , which predominated when employing sodium hydride as base. After screening a number of different conditions the use of sodium hydroxide in DMF was found to be optimum, giving a 2:1 ratio of 4 : 8 and allowing for isolation of 57% of 4 after chromatography (Scheme ).…”