Nitroxide synthesis using the methyltrioxorhenium/hydrogen peroxide system

Abstract

Some secondary amines of varying structural type have been oxidized by the methyltrioxorhenium/hydrogen peroxide system to the corresponding nitroxides in excellent yield. These results, coupled with our earlier work using this system, indicate the striking parallel between this chemistry and that of the dioxiranes. While the yields in the dioxirane and methyltrioxorhenium/hydrogen peroxide methods are comparable, the latter method must be regarded as superior since it is catalytic. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:347–350, 1998

Chloroplast‐located flavonoids can scavenge singlet oxygen

“…S1), by improving the synthesis protocols proposed by Rozantzev & Krinitzkaya (1965), Hankovszky et al (1980), Hideg et al (1980), Kálai et al . (1998), and Murray & Iyanar (1998). DanePy is both a fluorescent and a spin probe, which reacts with 1 O 2 to produce the corresponding nitroxide radical, DanePyO, the fluorescence of which is then quenched by an energy transfer from the ‘donor’ dansyl to the ‘acceptor’ nitroxide moiety (Kálai et al ., 1998; Hideg et al ., 2002).…”

Spirocyclic Nitroxides as Versatile Tools in Modern Natural Sciences: From Synthesis to Applications. Part I. Old and New Synthetic Approaches to Spirocyclic Nitroxyl Radicals

“…Piperidine-type SNRs ( Figure 3 , 3 ) have been obtained via oxidation of the corresponding sterically hindered amines 4 with hydrogen peroxide or its inorganic and organic analogs (for example, with potassium peroxymonosulfate (OXONE) or meta -chloroperoxybenzoic acid [ m -CPBA]) [ 104 , 105 , 106 ]. Given that the oxidation step allows us to synthesize SNRs with high yields, the main problem is usually the synthesis of a precursor, a respective amine.…”

“…For example, refluxing 2-amino-2-methylpropan-1-ol 340 with 1,4-cyclohexanedione 157a in the presence of PTSA readily leads to cyclic trans -bisamine 350 , the treatment of which with m -CPBA generates the trans -isomer of SNDR 351 in a 50% yield [ 191 ]. When the methyltrioxorhenium/H 2 O 2 system is employed at the second step as an oxidizer, the diradical yield can be increased to 80%, [ 106 ], and in an Oxone/acetone mixture, this yield can reach 90% [ 105 ] ( Scheme 65 ). An X-ray study of SNDR 351 revealed that both N -oxyl groups in the molecule are trans -diequatorial, with an intramolecular distance for the N atoms of 5.75 Å and the oxygens of 7.00 Å [ 192 ].…”