Ring transformation of 4-acylmethyl-2-chloro-4-hydroxy-2-cyclobutenone to γ-acylmethylenetetronate by thermal rearrangement: New synthetic aspect of squaric acid as a C4-synthon

Article abstract of DOI:10.1016/S0040-4020(01)85262-5

Title cyclobutenones prepared from the TiCl₄-catalyzed addition of a silyl enol ether to squaric acid dichloride and ester chloride were subjected to thermolysis (reflux in an aromatic solvent), and γ-acylmethylenetetronates were obtained stere