S. Ohira et al., GENERATION OF ALPHA-ALKOXYCARBONYL ALKYLIDENECARBENES - SYNTHESIS OF T-BUTYL CYCLOPENTENECARBOXYLATES, Tetrahedron letters, 36(48), 1995, pp. 8843-8844
Triflates of 2-hydroxymethylene t-butyl esters, derived from simple t-
butyl esters, were treated with potassium t-butoxide in THF to generat
e alkylidenecarbenes. At room temperature, they underwent intramolecul
ar 1,5 C-H insertion giving t-butyl t-butyl cyclopentenecarboxylates.