3H-indole

From the preceding examples it can be seen that oxidants and electrophilic reagents attack pyrroles and furans at positions 2 and 5 in the case of indoles the common point of attack is position 3. Thus autoxidation of indoles e.g. 99) gives 3-hydroperoxy-3H-indoles (e.g. 100). Lead tetraacetate similarly reacts at the 3-position to give a 3-acetoxy-3H-indole. Ozone and other oxidants have been used to cleave the 2,3-bond in indoles (Scheme 30) (81BCJ2369). 

H-Indole, 3,3-dichloro-synthesis, 4, 369 3H-Indole, 3,3-dimethyl-synthesis, 4, 224 3H-Indole, 3-hydroperoxy-autoxidation, 4, 247 rearrangement, 4, 249 3H-Indole, 3-oximino-synthesis, 4, 209, 210 3H-Indole, 3-oximino-2-phenyl Beckmann rearrangement, 4, 210 Indoleacetic acid synthesis, 4, 337 Indole-3-acetic acid as growth regulator, 4, 372 synthesis, 4, 346 Indole alkaloids, 4, 373 synthesis, 4, 276... 

UV spectroscopy, 4, 178, 179 vertical resonance energy, 4, 191 Vilsmeier-Haack formylation, 4, 221, 222 3H-Indoles... 

An alternative form of spiro nomenclature more common in Europe than in America is similar to that used in examples (64)-(66), but the order of citation of components is based on size, and the term spiro appears between the component names (see lUPAC Blue Book B-79MI10200) Rule B-11). Thus (64) would be called 3H-indole-S-spiro-l -cyclopenta-2, 4 -diene, and (63) would be cyclohexanespiro-4 -[l,3]dithian-2 -spirocyclopentane. 

Ab Initio Results for 1H-Indole and 3H-Indole (Energies in Hartrees) (99UP1)... 

Athoxy-3-a1kyl-3H-indole ergeben mit Natriumboranat in Essigsaure Indole (in Athanol erfolgt keine Reduktion)1 ... 

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

Ebenfalls mit guten Ausbeuten wird 3-Phenylimino-2-phenyl-3H-indol-l-oxid unter Reduktion einer N-Oxid-Funktion aus dem Bis-oxid I erhalten2 ... 

A mixture of 2-indolinone 187 (6.66 g, 50 mmol), pyrrohdine (12.52 mL, 150 mmol), and HMDS 2 (15.5 mL, 75 mmol) is heated under reflux for 3 h with TSOH H2O (0.475 g, 2.5 mmol) under argon in an oil-bath at 125-130°C. After 1 h 188 starts to crystallize. After cooling to 24 °C the crystals of 2-pyrrohdino-3H-indole 188 are isolated by filtration and washed with acetone to give 7.07 g (76%) sand-colored crystals, m.p. 140-142 °C, which can be readily recrystalhzed from boiling acetone under argon [27] (Scheme 4.56). 

Indigo (or 2-( 1,3-dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indol-3-one) (Fig. 5.7.1) is an example of a water-insoluble dye, contributing to its resistance... 

Spiro[3H-indole-3,5(4.H)-(l,2,4)triazoline]-2-one derivatives 204 have been obtained using microwave irradiation in the reaction between imines of isatin 203 and nitrile imines generated in situ from the corresponding hydrazonyl chlorides 199 (Scheme 9.63). The yields are in the range 85-95% and the reaction is complete within 5 min [110]. Similar reactions performed under thermal conditions were complete in 6-10 h and yields decreased to 20-30%. However, when the reaction was performed at ambient temperature, the products were obtained in excellent yields but only after a prolonged reaction time (30 h). 

Alternatively, diazotization of ethyl indole-2-carboxylate (179) leads to formation of 2-carboethoxy-3-diazo-3H-indole (180) which undergoes rhodium-catalyzed alcohol O-H insertion reactions leading to 3-alkoxyindoles 181 <00TL6905>. 

With phenylhydrazine, a mixture of pyrazoles 587 and 3H-indoles 591 were formed via conjugate addition, C=C bond migration and cyclic animation of the nitrile group or [3,3]-sigmatropic rearrangement of 3-amino-3-alkenenitriles 585, respectively [268a],... 

Taguchi and associates (117) treated 3,3-dimethyl-3H-indole with p-chloroben-zoyl chloride in pyridine, and obtained two crystalline compounds in addition to l-(p-chlorobenzoyl)-3,3-dimethylindolin-2-ol. These two products had the molecular formula C27H25ON2CI, and a tricyclic structure with two benzo moieties was assigned. Dave and co-workers (118) questioned the structure on the basis of mechanistic considerations, and presented evidence that the products are atropisomers of 1 -(p-chlorobenzoyl)-2-(2,3-dimethyl-1 -indolyl)-3,3-dimethylin-doline (75) about the C—N axis. The barrier to rotation about the C—N bond... 

Litvinov YM, Shestopalov AA, Rodinovskaya LA, Shestopalov AM (2009) New convenient four-component synthesis of 6-amino-2,4-dihydropyrano 2,3-c pyrazol-5-carbonitriles and one-pot synthesis of 6 -aminospiro (3H)-indol-3,4 -pyrano 2,3-c pyrazol -(lH)-2-on-5 -carbonitriles. J Comb Chem 11 914—919... 

The solid state photochemical reaction of indole with 1,4-naphthoquinone yielded 5H-dinaphtho(2,3-a 2, 3 -c)carbazole-6,ll,12,17-tetrone in addition to 2-(3-indolyl)-1,4-naphthoquinone which was also the only product in the solution photoreaction. Solventless thermochemical reactions of indole with phenanthrenequinone in the presence or absence of zinc chloride gave 10-(lH-indol-3-yl)-9-phenanthrenol and 9,10-dihydro-9-(lH-indol-3-yl)-10-(3H-indol-3-ylidene)-9-phenanthrenol or 10,10-di-lH-indol-3-yl-9(10H)-phenanthrenone, respectively. All of these products were only obtained in trace amounts in corresponding solution reactions, and are different from the adduct 10-hydroxy-10-(lH-indol-3-yl)-9(10H)-phenanthrenone obtained in the solution photoreaction (Wang et al., 1998). 

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. 

Upon reaction with nitrous acid, indole produces a complex mixture of products. In addition to 3-oximino-3H -indole (16), which is the stable tautomeric form of 3-nitrosoindole (17), dimeric products of the type (18) and (19) are also formed. In contrast, (16) appears to be the sole product of the nitrosation of indole with amyl nitrite and sodium ethoxide (72HC(25-2)537). Studies of the nitrosation of pyrrole are somewhat indecisive. The mononitrosopyrrole, obtained from the reaction of pyrrole with nitrous acid, has not been fully characterized, but there is some evidence that nitrosation of pyrrole with amyl nitrite and sodium ethoxide leads to the sodium salt of the 3-nitroso derivative. However, upon the addition of acid, the product rearranges to give the oxime of 3-formylisoxazole (20) (B-77MI30502). 

Alkylation of 2,3-disubstituted indoles generally leads to the formation of 2,3,3-trisub-stituted 3H-indoles, but it has been claimed that if the six-membered ring is activated to electrophilic attack, Friedel-Crafts alkylation occurs at the 5- or 6-positions (79MI30500). 

C-Aminoindoles autoxidize extremely rapidly. Consequently, comparatively few chemical reactions have been examined. The 2-amino derivative exists in the 3H-indole tautomeric form (473) and is protonated and alkylated on the annular nitrogen atom (72HC(25-2)179). The 1-methyl derivative (474) exits predominantly as such and not as the alternative 2-imino-3//-indole tautomer and is protonated at the 3-position to give a cation having the same electronic structure as that of the protonated (473). Acylation of (473) yields l-acetyl-2-acetylaminoindole, via the initial acylation of the annular nitrogen atom. Confirmation of this route has been established by the observation that 2-acetylaminoindole, obtained by hydrolysis of the diacetylated compound, is acetylated under identical conditions... 

Polyalkylated 2- and 3-pyrrolenines (2H- and 3H-pyrroles) and 3-indolenines (3H-indoles) are formed by methylation of the parent 1H heterocycles (see Section 3.05.1.2.7), but the acid-catalyzed or thermal rearrangement of 2,2,5-trisubstituted 2H-pyrroles and of 3,3-disubstituted 3//-indoles yields the corresponding 2,3,5-trisubstituted IH-pyrroles and the 2,3-disubstituted l//-indoles, respectively (see Section 3.05.1.1). 

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