The Study of Generating Stabilized Phenyl Cations by Using New Super-Leaving Groups

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Various alkali metal, alkali-earth metal, and transition metal ions ion-paired with weakly-coordinating polyfluorinated organic anions such as OSO_2CF_3, N (SO_2CF_3) _2, and C (SO_2CF_3) _3 were examined as strong Lewis acids in catalytic Diels-Alder reactions and halochromism of azo-dye compounds in nonpolar organic solvents to investigate the coordinating and leaving abilities of the organic anions.The photosolvolysis of aryl triflates in fluorinated alcohols was proved to proceed via aryl cation intermediates, while the photo-and thermal-solvolysis of aryl ester ArOS (O) (CF_3)=C (SO_2CF_3) _2 gave the products derived from the ArO-S (O) bond cleavage.The experimental relative rate-constant for the dediazoniation reactions of para- and meta-substituted benzenediazonium ions in solution was good correlated with the computational relative stabilizing energy of the corresponding phenyl cations with para- and meta-substituents, respectively. The phenyl cations with electron-donating substituents on meta-position are highly stabilized by novel direct-conjugation with the meta-substituents.Experimental evidences of this novel effect of meta-substituent for stabilizing phenyl cation intermediates in the thermal-solvolysis of the aryl triflate with piperidinyl groups at 3,5-positions were demonstrated : exclusive formation of solvent-substituted products and solvent polar effect in the solvolysis in TFE,HEIP,and aqueous HFIP indicated the S_N1 mechanism of the solvolysis to proceed via ary1 cations highly stabilized by the meta-substituents.