Pyridine N-oxides 3 are exclusively formed under particularly mild conditions when perfluorinated dialkyloxaziridines 1 are reacted with pyridine derivatives 2 bearing a substituent at the 2-position. Starting from pyridines substituted at the 3- and 4-positions, the previously unreported N-perfluoroacylpyridiniumaminides 4 are also produced and isolated as solid, stable compounds. Bis(pyridinium-N-aminides) 9, which have been prepared starting from bis-pyridine substrates and pyridazine and quinoxaline starting materials, also show the same reactivity. This behaviour reveals how oxaziridines 1 can work as both aminating and oxygenating agents
Alkyl-substituted olefins are epoxidized by perfluoro-cis-2,3-dialkyloxaziridines under particularly mild conditions. Electron deficient substrates (e.g. alpha,beta-enones) can also be epoxidized, and the more electron poor the double bond is, the more severe the reactions conditions become. The epoxidation is chemoselective (secondary alcohols and their ethers do not interfere), site selective (the monoepoxide of a diene can be obtained), and stereoselective (cis-alkenes afford cis-epoxides). Various complex and polyfunctional substrates of natural origin (monoterpenes, sesquiterpenes, steroids) have been transformed effectively.
Compounds containing the thiophosphoryl moiety (PdS) have found diversified applications in chemistry. They have been employed as chiral auxiliary agents in extraordinarily diastereoselective alkylation reactions, 1 in the resolution of racemic phenols 2 and in the determination of the optical purity of alcohols and amines. 3 Thiophosphoryl derivatives also proved useful in a vast number of biological investigations. They are effective tools for the study of enzyme-catalyzed reactions, 4 potent inhibitors of metalloproteases, 5 and promising candidates for use in oligonucleotide therapeutics. 6 All of these properties are obviously shared by the substances possessing the phosphoryl group (PdO). 1-6 An easy transformation of the thiophosphoryl into phosphoryl compounds would provide a much greater flexibility in preparing and studying chemical and biological properties of both classes of tetracoordinated phosphorus compounds.In the course of a study on the oxidation of some organophosphorus agrochemicals by perfluoro cis-2,3dialkyloxaziridines 1a,b, 7 we noticed that these oxaziridines were able to transform phosphorothioates into corresponding phosphates. The noteworthy effectiveness of the observed reaction prompted us to test the conversion of the thiophosphoryl into phosphoryl group on other structurally different phosphorus(V) derivatives, and here we describe the generality of the process.When trialkyl-and triarylphosphine sulfides 2a-d were reacted with equimolar amounts of the oxaziridine 1a in an halogenated solvent at room temperature, high yields of the corresponding oxides 3a-d were formed (eq 1). Reactions were complete in less than 5 min, and the only observed coproducts were the azaalkene 4a, as shown by 19 F NMR of crude reaction mixtures, and elemental sulfur, as proven by microanalyses and exact mass of the formed yellowish solid. Similarly, triphenylphosphine selenide (2o) afforded quantitatively the corresponding oxide 3c and elemental selenium in few minutes at -40°C.High yields of phosphoryl products were obtained also when alkoxy and amido residues were bound to the phosphorus atom. Under the usual reaction conditions alkylthiophosphonates and (difluoromethylene)thiophosphonates, 2e and 2f, respectively, afforded nearly quantitative yields of the corresponding phosphonate 3e,f. Some commonly employed agrochemicals 8 and their metabolites such as Parathion (2g) and its O-methyl analogue (2h), Fenitrothion (2i), Bromophos (2j), the sulfinyl derivatives of demethon-O (2l), and demethon-O-methyl (2k) all have a dialkyl aryl or trialkyl phosphorothioate moiety which is oxidatively desulfurized cleanly to give corresponding phosphate products 3h-l. At room temperature the reaction occurs very rapidly also on these substrates, but best yields are obtained performing the desulfurization in the cold for longer reaction times (Table). Side reactions are thus avoided (partial hydrolyses of labile p-nitrophenoxy residue in 2g-i or sulfinyl to sulfonyl oxidation in 2k,l).The diethylthiophosphoramidate ...
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