REACTIONS OF ALCOHOLS WITH CESIUM FLUOROXYSULFATE

The reactions of alcohols with cesium fluoroxysulfate (CsSO4F) in MeCN suspension were studied, and the role of the structure of the alcohol and the reaction conditions on the course of reaction was determined. Secondary benzyl alcohols bearing a nonactivating aromatic ring were selectively oxidized to the corresponding ketones, while the CsSO4F-me diated reaction of phenyl-1-naphthylmethanol resulted in the formation of 1-fluoronaphthalene and benzaldehyde. Cyclic and noncyclic seconda ry alcohols were readily converted to ketones, as well as 1-hydroxyben zocyclanes to benzocyclanones-1, without any further fluorination or o xidation under the reaction conditions. On the other hand, reactions o f primary alcohols with CsSO4F resulted in the formation of acid fluor ides derived from further fluorination of aldehydes. Another type of t ransformation was observed in the case of alcohols bearing a benzyl fu nctional group attached geminal to a hydroxy group, where decarbonylat ion of reactive intermediates resulting in the formation of benzyl flu oride derivatives became the main process. 2-Phenylethanol was so conv erted to benzyl fluoride and phenylacetyl fluoride in a 3:1 relative r atio, while 2-phenyl-1-propanol was selectively transformed to 1-pheny l-1-fluoroethane. The presence of the radical inhibitor nitrobenzene i n the reaction mixture considerably inhibited conversion of the starti ng material, The same effect was observed by lowering the solvent pola rity. Hammett correlation analysis of the effect of substituents on th e reaction rates of oxidation of a set of substituted l-phenyl-l-ethan ols to acetophenones gave the reaction constant rho(+)=-0.32, while an alysis of analogous data for the transformations of benzyl alcohols to benzoyl fluorides gave the value of -0.54, A mechanism including radi cal intermediates was proposed for the transformation of alcohols by C sSO4F.