Indol-1-oxid

Arylimino-2-phenyl-3H-indol- 1-oxide werden zusatzlich an der Imino-Gruppe reduziert2 ... 

HjC—COONa H5C2—OH A 0 Ar OH 2-Aryl-3-hydroxy- indol-1-oxide 50-75 1 (s.a. H6)... 

Isatogens (1) and indolones (2) are brightly colored solids that do not occur naturally. Isatogens (I) are more comprehensively named as 3-oxo-3//-indole 1-oxides, or as the 1-oxides of indolones (2), 3-oxo-3H-indoles, or 3//-indol-3-ones. Both series of compounds are numbered in accordance with IUPAC rules. Isatogens were first reported in 18811,2 and the first indolone in 1912.3 Isatogens (1), indolones (2) and indoxyls (3) form an interrelated redox system. Indolones in which there is a methylene or methine substituent in the 2-position tautomerize to the preferred 2-methylene-3//-indol-3-one (indogenide) structures (4).4 Only passing reference will be made to 3 and 4 in this review. 

CPB3678) and the ester (Table IV) show that these compounds exist entirely as the hydrogen-bonded 1-hydroxy tautomers, but in contrast, 3-bromo-l-hydroxyindole-2-carboxylic acid appears to favor the 3H-indole 1-oxide form [68JCS(C)504]. Only the 1-hydroxy tautomer was observed in a number of cases in deuteriochloroform and in hexadeuterio-dimethylsulfoxide solutions (83JOC3639). 

A small number of 3-hydroxy-2-phenyl-3//-indole 1-oxides (128) have been prepared [80JCS(P2)339] from the 3-substituted (R = Me or Ph) indoles (127) by stirring benzene solutions in air. Reduction with sodium borohydride gave the indolines 129 which, with ethanolic hydrogen chloride, gave back the indoles (127). The similar acid-catalyzed dehydra-... 

The NMR spectrum of 5-bromo-l-hydroxyindoIe-2-carboxylic acid,78 in comparison with the spectra of related compounds, suggested that the compound is present as the tautomeric 3H-indole 1-oxide in CDC13 (11a).79... 

Indolenines exemplified by compound (336) can be converted into the related 3/f-indole 1-oxide (338) by a sequence involving reduction to the dihydro compound (337) followed by oxidation with /M-chloroperbenzoic acid. Compound (338) behaves as a typical cyclic nitrone and undergoes cycloaddition with DMAD and methyl propiolate. The initially formed cycloadduct (339) rearranges via an aziridine intermediate to an oxazolo[3,2-a]indole (340) (Scheme 107) <93JCS(Pl)939>. 

Myers AG, Herzon SB (2003) Identification of a novel Michael acceptor group for the reversible addition of oxygen- and sulfur-based nucleophiles. Synthesis and reactivity of the 3-alkylidene-3H-indole 1-oxide function of Avrainvillamide. J Am Chem Soc 125 12080-12081... 

Letcher RM, Sin DWM et al (1993) Oxazolo[3,2-a]indoles, pynolo- and azepino[l,2-a] indoles fiom 3H-indole 1-oxides and acetylenecarboxylic esters by skeletal rearrangements. J Chem Soc Perkin Trans 1 939-944... 

Two sohd-phase syntheses of Af-hydroxy(alkoxy)indoles have been reported by Roy (equation 1) [91] and Wu (equa-tion2) [92] respectively (Scheme 15).TheAf-hydroxyindoles in equation 2 were alkylated regioselectively to give a library of 1,2-dialkoxyindoles after cleavage from the SynPhase lanterns [92]. In a program toward the synthesis of the alkaloids avrainvillamide and stephacidin B, Myers and Herzon synthesized 3-alkylidene-3//-indole 1-oxide (equation 3), which is the keystone unit of these novel alkaloids [93]. 

Scheme 15 Solid Phase Reductive Cyclization Indole Synthesis and Myers 3-Alkylidene-3H-indole 1-Oxide Synthesis...

Dopp, D., Photoisomerization and acidolysis of 3,3-dimethyl-3H-indole 1-oxides, Chem. Ber., 109, 3849, 1976. 

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