Catalytic Synthesis of Terminal Epoxides via Methylene Transfer to Aldehydes

Significance

Connon’s group reports a highly ­efficient protocol for the synthesis of terminal epoxides via a catalytic methylene transfer reaction to aldehydes. The use of a simple sulfide catalyst in combination with stoichiometric amounts of MeOTf and the P₂ phosphazene base resulted in the in situ generation of a reactive sulfur ylide. Subsequent methylene transfer to aromatic as well as α-branched aliphatic aldehydes furnished the desired epoxides in high yields. With newly synthesized chiral sulfides the authors report a catalytic asymmetric version of their reaction as well, although only moderate enantioselectivities have been obtained so far.