Rhodium(II)-catalyzed addition of 2-diazo(fluoroalkyl)acetoacetates to sulfides: a simple synthesis of stable sulfonium ylides

2-Diazo(fluoroalkyl)acetoacetates 1 reacted readily with many sulfides under mild reaction conditions in the presence of catalytic Rh2(OAc)4 affording to the corresponding sulfonium ylides. While thianthrene gave trans-thianthrenium 5,10-di(fluoroalkylacetoethoxycarbonyl)methylides (7a and 7b) under the same reaction condition, the structure of 7b trans-thianthrenium 5,10-di(bromodifluoroacetoethoxy-carbonyl)methylides was fully confirmed by spectral methods and X-ray single crystal diffraction analysis. All the ylide products obtained are fairly stable due to the strong electron-withdrawing properties of the fluorine atom.