摘要:
The tridentate ligand of iodinane 7, with electronegative apical oxygens joined by five-membered rings to an electropositive equatorial carbon, strongly stabilizes pseudo-trigonal-bipyramidal (PSI-TBP) 10-I-3 species 7, as well as 10-I-4 species such as iodinane oxide 5. Fluorination of 7 forms a pseudooctahedral (PSI-Oc) 12-I-5 periodinane, 4, which is easily hydrolyzed to 5, or reacts with Lewis acids to form 10-I-4 fluoroperiodonium cation 8. The equatorial I+-O- bond of 5 reacts with electrophiles at the oxygen [with trifluoroacetyl triflate (TFAT) to give 10-I-4 (trifluoroacetoxy)periodonium triflate 12; with triflic acid (TfOH) to form the 10-I-4 hydroxyperiodonium triflate 9; and with trifluoroacetic anhydride (TFAA) to form the 12-I-5 bis(trifluoroacetoxy)periodinane 11]. Small amounts of tetrabutylammonium hydroxide give nucleophilic addition to the iodine of 5 to form 12-I-5 intermediates (18) leading to rapid inversion of geometry at the 10-I-4 center of the iodinane oxide. Excess KOH cleaves the C-I bond of 5, forming the reduced arenediol 17. Diphenyldialkoxysulfurane 14 converts 5 to dialkoxyperiodinane 13, forming diphenyl sulfoxide. Iodine oxide 5 is a strong oxidizing agent, rapidly oxidizing HCl to Cl2, or pinacol to acetone. Oxidation of a diaryl sulfide to the sulfoxide and the sulfone occurs unselectively, but slowly, at 160-degrees-C with pure 5. With a catalytic amount of TFAA, selective oxidation of the diaryl sulfide to the sulfoxide by 5 is rapid at room temperature.