Oxidation of Nitrogen-Containing Compounds

Excitation of the bichromophoric 3p- [2-(methoxycarbonyl)bicyclo[2.2.1]-hepta-2,5-diene-3-yI]carboxy androst-5 -en-17 P-yl-2,2, 6,6, N, N, N, N -heptamethyl-benzidine induces electron transfer to the norbornadiene chromophore to give a 

The order of their effectiveness as photosensitizers for the oxidation of glycyltryptophan in aqueous solution is nicotinic acid nicotinamide nicotine-hydroxymethylamide these reactions seems to involve the superoxide radical anion. 

A time-resolved study of the decay kinetics of transient radicals produced from 2,2,4,6-tetramethyl-l,2-dihydroquinoIine in both aqueous and micellar solution has appeared, and sanguinarine, a benzophenanthridine plant alkaloid, has been photooxidised to oxysanguinarine in an irreversible singlet state process. Pyrrolo-[2,3-b]indole (77) has been produced with some enantioselectivity by photosensitized oxygenation of Nb-(methoxycarbonyl)tryptamine in the presence of (-)-nicotine, and irradiation of 3-methylindole on a CdS surface and under 

The photoinduced intramolecular electron transfer reactions of some poly-(ethylene glycol)-linked 9-aminoacridine-benzoate electron donor-acceptor systems have been described. Photosensitized oxidation of 5-methyl-2 -deoxy-cytidine using menadione (2-methylnaphthalene-l,4-dione) gives 5,6-dihydroxy-5,6-dihydro-5-methyl-2 -deoxycytidine in what is thought to be an electron 

C02Me) in the presence of 2,4,6-triphenylpyrylium tetrafluoroborate as sensitizer gives cyclopropenes together with 2H-pyrroles which arise by solvent addition to the 1,3-radical cation intermediate. Phenylmercaptotetrazole has been photo-catalytically oxidised on aerated Ti02 dispersions (Xjn- 330 nm) and a mechanism suggested which involves the formation of CO2, S04, NOa, and NH4. Photooxidation of phenothiazine in either benzene or cyclohexane in the presence of molecular oxygen has been shown by EPR experiments to give the phenothiazine nitroxyl radical rather than the radical cation. These observations are supported by the results of AMI calculations. The photooxidation of Azure A (81) as well as its fluorescence properties have been studied in the presence of P-cyclodextrin, and this has enabled an induced fluorimetric method to be developed for the determination of (81).  

The oxidation of NO and N02 is of industrial importance for cleaning combustion-flue gases. Transition metal ion-exchanged zeolites have been shown (51) to be highly active catalysts for this reaction. The relative activities are shown in Fig. 10, from which it can be seen that equilibrium conversions of NO to N02 can be achieved with Cu2 + X at reaction temperatures as low as 350 C. Kinetic studies showed that the reaction rates were fractional order in both NO and 02. The following reaction mechanism was therefore proposed, for example, with Cu2 + X, 

This mechanism would seem to be quite plausible since there is good evidence for the formation of both nitrosyl (51-55) and oxygen-bridge complexes (16 26) with transition metal ions in zeolites. Interestingly, for a Cr3 + Y catalyst (51), the activity was enhanced by HzO and there was no deactivation by S02, indicating that such a catalyst would likely be quite robust under practical feed conditions. 

Williamson et al. (56) showed that Cu2 + Y was an active catalyst for the oxidation of NH3 to N2 and H20. A mechanism was proposed involving the intermediate formation of an amine complex [Cu(NH3)4]2+. The NH3 reduction of Cu2+ and Cu+ in this complex was proposed as the slow step with reoxidation via 02 being very rapid. This mechanism was consistent with the kinetic expressions which were shown to be first order in NH3 and zero order in 02. 

Sensitised photooxidation of tert-butyl 3-methoxypyrrole-2-carboxylate in methanol gives tert-butyl 3,5-dimethoxypyrrole-2-carboxylate together with a bipyrrolic oxidative coupling product (48). A novel ring cleavage of 4,5-bis(4-fluorophenyl)-a,a-bis(trifluoromethyl)-lH-pyrrole-2-methanamine (49) using 02( Ag) followed by acid catalysed dehydrocyclisation leads to the 4,4-bis(tri-fluoromethyl)imidazoline (50) which can be derivatised into (51), a compound which has acyl Co A cholesterol acyltransferase activity. 2-Imidazolidinethione 

An examination of photoelectron transfer within multifunctional porphyrin and ubiquinone analogues linked by H-bonding interactions which serve to hold the donor and acceptor in a co-facial orientation, has been made, and is the first example of electron transfer between such structures which is complete within the picosecond range.Irradiation of colloidal syn-tetraresorcinolporphyrin having eight alkylphosphocholine side-chains (octopus porphyrin), and of the corresponding Zn(II) complex in the presence of hydrophobic phenyl-p-benzoquinone or hydrophilic naphtho-l,2-quinone-4-sulfonate, induces electron transfer to the quinone electron transfer to is also reported.A study has been made of 

Pyridine has been photo-oxidized to pyridine N-oxide using singlet oxygen generated by dye photosensitization. The sensitized photo-oxygenation of 2,4,4,6-tetraphenyl-l,4-dihydropyridine has been described, and appears to be solvent dependent. In acetone or cyclic ethers, (28 R = OOH, R = H) is 

The dioxetane (29) has been obtained quantitatively by photo-oxygenation of 9-(2-adamantylidene)-iV-methylacridan in CH2CI2 at -72 C using Methylene Blue as sensitizer. In toluene at 25 °C, (29) is catalytically decomposed by lanthanide chelates with energy transfer. Base-induced oxygenation and chemiluminescence of 10-methylacridinium and 1-methylquinolinium salts have been observed in DMSO. The chemiluminescence has its origin in 

Reaction of pyrrole with benzaldehyde-3,5-disulphonic acid to give a porphyrin is autophotosensitized/ and regioselective photo-oxygenation of 2-aryl-4,5,6,7-tetrahydroindoles (30) to form the indolenines (31 R = H, Me, Cl, or Br) has been accomplished by irradiation of (30) in oxygenated 

Under aerobic conditions, irradiation of phenothiazine in the presence of riboflavin leads to its photo-oxidation to the corresponding sulphoxide, presumably via the agency of singlet oxygen. The reaction is retarded by /3-cyclodextrin although not by a- and y-cyclodextrins, and this has been 

Amat-Guerri, M. Lopez-Gonzalez, and R. Martinez-Utiilla, Tetrahedron Lett., 1983,24, 3749. 

Examples for the oxidation of nitrogen-containing compounds via halide ions as redox catalysts are listed in Table 4, No. 51-56. In this way, primary amines are transformed to nitriles using the system NaBr/MeOH (Table 4, No. 52) Thus, 1,2-diaminocyclohexane is cleaved to yield adiponitrile (Eq. (64)) 

Quite important is also the a-methoxylation of A -carbomethoxylated a-amino acid esters and a-amino-p-lactams (Table 4, No. 53-55) a-Methoxylation was 

4-O2NC6H4, 2-pyridinyl, benzothiazol-2-yl) gives methanols (21 R = OH, R same) and ketones,213 and oxothiochrome (22) is formed by photochemical oxidation of aqueous solutions of thiochrome, using 02(1 Ag) generated from Rose Bengal adsorbed on Sephadex G-25.214 Dialkyl phosphite inhibition of the photooxidation of 4-(p-tolylazo)-l-naphthol with 02(1 Ag) has been employed as an indicator of reaction in the kinetic determination of dialkyl phosphites and some aromatic aldehydes.2l5 

A number of papers contribute to an understanding of the mechanistic features of the photo-oxidation of A -containing compounds. A labelled guanosine 

The structure of oxidized radicals obtained by reaction in water of hy-droxypyrimidines with HO, 0 , S04 , Br2 (generated by in situ photolysis or radiolysis) have been determined by EPR spectroscopy. 2-Hydroxypyrimidine 

The oxidation of N-containing compounds also features in a number of papers which are broadly synthetic in scope. The generation of the amide radical cation in a homobenzylic amide, using the photooxidant N-methylquinolinium hexa-fluorophosphate (NMQPF ), selectively weakens the benzylic carbon-carbon 

The oxidative cyclization of 4-(2-styryl)- (150, R = Ph) and 4-(2-naphthyl-vinyl)- (150, R = naphthyl) benzo[a]quinolizinium salts affords 6a-azoniapicene (151) and 6a-azoniabenzo[6]picene (152) salts, respectively. Interestingly the corresponding pyridyl compound (150, Ar = 2-pyridyl) undergoes a five-mem-bered ring cyclization, giving a 3b-azonia-5-(2-pyridyl)acephenanthrylene salt (153). No explanation is provided. Finally, the ET sensitized 1-aza-di-jt-methane 

A number of examples of the use of host-guest chemistry in the creation of PET active systems have appeared. The reaction of P-cyclodextrin alcoholate with meso-tetrakis(pentafluorophenyl)porphyrin is reported to give a hydrophilic cyclodextrin-porphyrin conjugate in 14% yield. ° In the presence of guests such as 1,4-benzoquinone, anthraquinone-2-sufonate or 8-anilino-l-naphthalene sulfonic acid, PET operates as evidenced by the fluorescence 

In the presence of Rose Bengal as sensitizer and under either aerobic or anaerobic conditions, proline is photodecarboxylated to A -pyrroline, and under similar conditions the methyl ester yields an equimolar mixture of A -and A -pyrroline-2-carboxylic acid methyl esters. These observations suggest that the reaction proceeds by a Type I photooxidation. 

A ns laser flash photolysis study of peptides composed of alanine (Ala) and tryptophan (Trp), modified with the (nitro)pyrenesulfonyl chromophore (Pyr and NPyr), reveals the existence of a triplet excited state local to the pyrene 

Using Rose Bengal as sensitizer, isoquinoline-1,3-diones have been oxidised by 02( Ag) to such products as isoquinoline-1,3,4-triones, methyl 1 -hydroxy-3-oxoisoindole-1 -carboxylates, and 3-hydroxy-3-alkyl(aryl)amino-carbonylbenzoisofuran-l-ones, depending upon the solvent chosen. 02( Ag) generated using tetraphenylporphyrin has also been used, in which 

A time resolved CIDEP study of radical pair systems derived by electron-transfer photooxidation of carbazole derivatives using maleic anhydride has revealed that the singlet state of the radical ion-pair has an energy which is greater than that of the triplet state. From this evidence the conclusion is drawn that the sign of the apparent exchange interaction is positive. 

The photooxidation of oxopurines such as caffeine, theophylline, theobromine, and 1,3,7-trimethyluric acid using Rose Bengal as sensitizer occurs by a type II mechanism. 3-Methyl-5-(methylamine)-l,5-dehydrohydantoin has been characterised as a reaction product, and evidence is presented which suggests that the initial exciplex formed between 02( Ag) and the oxopurine evolves into a zwitterionic transition state. 

Tokida, K. Okada, and T. Mukai, Fukusokan Kagaku Toronkai Koen Yoshishu, 12th, 1979, 221. 

Hydroperoxyindolines have been trapped by reduction with KBH4. In the photo-oxidation of aqueous indole-3-acetic acid and of its methyl ester using various sensitizers at different pHs, cleavage by singlet oxygen appears to compete with hydroperoxidation of the CH2 group. The mechanism of photo-oxidation of bacteriochlorophyll C derivatives has also been examined.  

Matsugo, I. Saito, and T. Matsuura, Kokagaku Toronkai Koen Yoshishu, 1979, 202. 

Yamane, H. Shimazu, and T. Matsuura, Tetrahedron Letters, 1975, 641. 

Herlem, Y. Hubert-Brierre, F. Khuong-Huu, and R. Goutarel, Tetrahedron, 1973, 29, 2195. 

Khuong-Huu, D. Herlem, and Y. Hubert-Brierre, Tetrahedron Letters, 1975, 359. 

Conflicting accounts of the dye-sensitized photo-oxidation of diphenylamine in alcohols have been published, with one group of workers152 reporting diphenylnitroxide as the product, and another group158 repeating their claim (see Vol. 6, p. 545) that iV-phenyl-p-benzoquinonimine is formed. The photo-oxidation of 2,4,6-triphenylpyridine TV-phenylimine may involve ozone production.154 

4-attack of 1Oa on the aromatic ring, followed by rearrangements. The conversion of the amine (103) into ring-cleaved product (105) in 60% yield is thought to involve the dioxetan (104), and to represent the first example of 1,2-addition of 2 to the benzene ring. 

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Finally, it is important to note that many of the anodic reactions discussed above cannot be duplicated with traditional chemical oxidants. For this reason, the anodic oxidation of nitrogen-containing compounds represents a powerful class of reactions that has the potential to open up entirely new synthetic pathways to complex molecules. From the work already accomplished, it is clear that employing such an approach is both feasible and beneficial, and that the ability to selectively oxidize amines and amides is a valuable tool for any synthetic chemist to have at their disposal. 

SCHEME 149. Molybdenum-catalyzed oxidation of nitrogen-containing compounds using tert-amyl hydroperoxide... 

Generally, hypervalent iodine reagents are often better than traditional reagents of similar reactivity, with respect to efficiency and chemoselectivity - sometimes even stereoselectivity. Unusual reactivity is another interesting feature which has often resulted in unexpected transformation. Examples of such reactions may be found in the oxidation of nitrogen-containing compounds, the Hofmann rearrangement in acidic conditions, the acetalization of carbonyl compounds in alkali, the remote functionalization of steroids, etc. Some unique transformations were effected in the... 

OXIDATION OF NITROGEN-CONTAINING COMPOUNDS, OTHER THAN... 

Anodic Oxidation of Nitrogen-Containing Compounds VII. AMINO ALCOHOLS AND AMINO ACIDS... 

Mineralization of chloro-ethylenes decreases with the increase in chlorine atom substitution on the C=C bond and oxidation of nitrogen-containing compounds is slow when compared to the compounds containing phosphorus, sulfur, and chlorine. Photooxidation in a mixture of organics is complicated as the rate of one compound may be inhibited or enhanced by the presence of others (4). 

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