Formation of 2-halomethylene-4-cyclopentene-1,3-diones and/or 2-halo-1,4-benzoquinones via ring-expansion of 4-ethynyl-4-hydroxy-2,3-substituted-2-cyclobuten-1-ones. Total synthesis of methyl linderone

An in-depth study of the reactions of 4-(ethynyl)-4-hydroxy-2,3-substituted-2-cyclobuten-1-ones with N-bromo- or N-iodosuccinimide, affording in most cases 2-halomethylene-4-cyclopentene-1,3-dione, is described. This reaction was used in a short total synthesis of methyl linderone.