Michaelis–Arbuzov Reactions of Perhalogenated Cyclobutenes with Trialkyl Phosphites

GRAPHICAL ABSTRACT

Abstract

1,2-Dihalo-3,3,4,4-tetrafluorocyclobut-1-enes, C₄F₄XY (X, Y = Cl, Br, I), and trimethyl phosphite, P(OCH₃)₃, undergo Michaelis–Arbuzov reactions to form stable 3,3,4,4-tetrafluorocyclo-but-1-ene-1,2-bisphosphonic acid tetramethylester. If X = F, Cl, Br, I, and Y = F then 1-halo-3,3,4,4-tetrafluorocyclobut-1-enyl-trimethoxyfluorophosphoranes are observed and isolated as intermediates of the Michaelis–Arbuzov reaction. Perchlorocyclobutene reacts with trialkyl phosphites, P(OR)₃ (R = CH₃, C₂H₅, iso-C₃H₇), to form 1,2-dihalo-3,3,4,4-tetrachlorocyclobut-1-ene-1,2-bisphosphonic acid tetraalkylesters and the isomeric 1,3,4,4-tetrachlorobuta-1,3-diene-1,2-bisphosphonic acid tetraalkylesters. Results from NMR and X-Ray studies are presented.

Keywords:

• Perhalocyclobutenes; Michaelis–Arbuzov; phosphoranes; phosphonic acid dialkylesters
• 1,3,4,4-tetrachlorobuta-1,3-diene-1,2-bisphoshonic acid tetraalkylesters