O-Alkoxy-N-oxides

Hydroxy and 3-hydroxy-5-alkoxy derivatives (260) result from the oxidation of imino-dicarbonates of type (344) (X = O, S, N) with hydrogen peroxide (Scheme 77 see also Equation (36)) <84CHEC-I(6)463>. Products of type (260) are also obtained from the reaction of imino-dicarbonates (267) with chloramine (see also Equation (38)). 

The oxygen atom has also been used to generate other functionalities, such as the aldehyde moiety in Kibayashi s syntheses of (—)-coniine (197) and its enantiomer (Scheme 1.43) (253). Here, reaction of tetrahydropyridine N-oxide 93 with a silylated chiral allyl ether dipolarophile 198 delivered the adduct 199 with the desired bridgehead stereochemistry via the inside alkoxy effect . Desilylation and hydrogenolytic N—O bond rupture with palladium(II) chloride provided the diol 200... 

Dithiophosphorsaure-O.O.S-trialkylester liefern mit Pyridin-N-oxid die 1-Alkoxy-pyridinium-salze der Di-thiophosphorsaure-S.S-dialkylester138 z. B. ... 

The pyrimido-pteridine N-oxide (38) can be used for the photohydroxylation of phenols in acetonitrile solution (Sako et al.). Wan and Wu have reported that irradiation of o-dialkoxybenzenes in aqueous acetonitrile containing sulphuric acid leads to replacement of the alkoxy groups by hydroxyl the mechanism appears to involve protonation of the Si arene to give a o-complex which then undergoes ipso attack by water. Fields has reported that diphenylmaleic anhydride photocyclises readily to the phenanthrene (39), and has corrected an earlier report that the product is a (2+2) dimer. 

Several /V- m e t hy L 9 - a c ri d i n e c a r b o xy I i c acid derivatives (e.g., 10-methyl-9-acridinecarboxylic chloride and esters derived therefrom [39]) are chemiluminescent in alkaline aqueous solutions (but not in aprotic solvents). The emission is similar to that seen in the CL of lucigenin and the ultimate product of the reaction is N melhylacridone, leading to the conclusion that the lowest excited singlet state of N melhylacridone is the emitting species [40]. In the case of the TV-methyl-9-acridinecarboxylates the critical intermediate is believed to be either a linear peroxide [41, 42] or a dioxetanone [43, 44]. Reduced acridines (acridanes) such as N methyl 9-bis (alkoxy) methylacridan [45] also emit /V- m e t hy I a c r i d o n e 1 i k e CL when oxidized in alkaline, aqueous solutions. Presumably an early step in the oxidation process aromatizes the acridan ring. 

N-Alkylation of 1-hydroxy-l,2,3-triazoles 443 produces 3-substituted 1,2,3-triazole 1-oxides 448 (R=Alk). Competing O-alkylation of the 1-hydroxy-l,2,3-triazoles 443 to give 1-alkoxy-l,2,3-triazole 458 is suppressed by omitting addition of base during the alkylation (1996ACSA549, 2001S1053, 2002JOC3904) (Scheme 132). 

The enantioselective synthesis of antimalarial (+)-febrifugine and (+)-isofebrifugine alkaloids was achieved through the 1,3-DC of (S)-5-alkoxy-2,3,43-lctrahydropyridine-l-oxide 76 with allyl alcohol followed by hydrogcnolytic N-O bond fission and suitable elaboration of the product <01OL953>. 

Williams P.A, Jones A.C., Bickley J.F., Steiner A., Davies H.O., Leedham T.J., Impey SA., Garcia J., Allen S., Rougier A., Blyr A. Synthesis and crystal structures ofdimethylaminoethanol adducts of Ni(ll) acetate and Ni(II) acetylacetonate. Precursors for the sol-gel deposition of electrochromic nickel oxide thin films, J. Mater. Chem. 2001, 11 2329 Yanovskaya M.L, Kotova N.M., Golubko N.V., Turova N.Ya. Reactions of magnesium and titanium alkoxides. Preparation and characterization of alkoxy-derived magnesium titanate powders and ceramics, J. Sol-Gel Sci. Tech. 1998 11 23... 

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