New asymmetric (salen)Mn III and UO 2 complexes containing a calix [4]arene unit in the ligand framework were synthesized. The UO 2 complexes were characterized by 1 H-, 13 C-, 2D TOCSY and T-ROESY NMR spectroscopy. Furthermore, the structure of one UO 2 complex was determined by singlecrystal X-ray analysis. The data showed that UO 2 complexes, which can be considered in first approximation models of the Mn=O oxidant active species, possess a chiral pocket and

The applicability of thianthrene 5-oxide as a mechanistic probe for distinguishing between the electrophilic and the nucleophilic character in oxygen-transfer processes from a series of Mo(V1) and W(V1) peroxo complexes has been investigated. In almost all the cases examined, the predominant formation of the corresponding sulfone has been observed. This would indicate a nucleophilic nature of the oxidants, which is, however, at odd with known chemistry of such species. In fact, competitive experiments performed by employing pchlorophenyl methyl sulfide and phenyl methyl sulfoxide together in equivalent amounts as substrates revealed the preferred oxidation of the former over the latter as expected for an electrophilic oxygen transfer. These apparently contrasting findings are interpreted in terms of an incursion of radical pathways in the oxidation reactions of thianthrene 5-oxide by these peroxo complexes.

The oxidation of thianthrene 5-oxide (SSO) by M0O5HMPT has been studied in 1,2-dichloroethane at 40 °C. Under conditions of excess substrate over the oxidant, three products are formed, i.e., two isomeric cis and trans bissulfoxides (SOSO) and sulfide-sulfone (SSO2) which quantitatively account for the active oxygen of M0O5HMPT consumed. The rates of appearance of the products at different reactant concentrations have been measured. A second-order rate law has been established. The ratios of the rate constants and of the final concentrations of the three products, i.e., &2(cis-S0S0):&2(fr'cms-S0S0):&2(SS02) = l.0:4.0:1.0; [ds-S0S0L:[£rcms-S0S0U:[SS02]~= 1.0:4.5:1.2, are in good agreement. The frans-SOSO-forming reaction is only 4-fold faster than that leading to SSO2. cis-SOSO and SSO2 are produced at almost the same rate. Evidence is presented that all the oxidation reactions are electrophilic processes taking place via a simple bimolecular mechanism not involving the coordination of the substrate to the metal. The low selectivity is due to the scarce reactivity of the thioether center in thianthrene 5-oxide. The investigation of the oxidative behavior of structurally related compounds reveals that such a low reactivity results from a combination of stereoelectronic effects. These findings provide a rationale to some ambiguous results obtained when thianthrene 5-oxide is employed as a mechanistic probe of the electronic character of the oxidants.

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Method 3. Of (IR*,2S *,5R *)-Bicyclo[3.3.0]oct-7-enendo-2-ol. (S)-O-Methylmandelic acid (1.00 g, 6.02 mmol) was added to a white suspension prepared by the slow addition of 0.578 mL (6.62 mmol) of oxalyl chloride to 0.698 mL (9.03 mmol) of DMF ip 20 mL of acetonitrile at 0 °C. After 5 min, a solution of 821 mg (6.62 mmol) of the title alcohol in 1.07 mL (13.2 mmol) of pyridine was added over a 5-min period and the resultant mixture stirred at 0 °C for 20 min. The pale yellow reaction mixture was diluted with 100 mL of ether, the organic phase washed twice with saturated aqueous cupric sulfate and dried over sodium sulfate, and the solvent removed in vacuo to give a yellow oil.

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A new heteroditopic chiral uranyl-salen complex incorporating two pyrenyl groups was designed and synthesized for the recognition of ammonium salts, tetrabutylammonium (TBA) and tetramethylammonium (TMA) amino acids. UV/Vis measurements indicate the formation of 1:1 host-guest complexes with high association constants and an excellent en-