Indole 2-phenylindole

For the mechanism of this reaction, see Robinson and Robinson,1918, H3i 639 1924, 145, 827.) The reaction is of wide application for example, the use of methyl-phenyl-hydrazine, CsH5(CHj)> -iN H, in the above reaction gives i-methyl-2-phenylindole, whereas pyruvic acid, CH CO COOH, when converted to its phenylhydrazone and then indolised, gives indole-2-carboxylic... 

The thermal chemistry of a number of aryl-substituted azirines often results in the formation of indole derivatives (68TL3499). Thus, heating a sample of azirine (152) gave 3-phenylindole (155) and dihydropyrazine (156). The formation of (155) was suggested to... 

Bruce and Sutcliffe obtained l-acetyl-2-methyl-3-phenylindole (123) by the action of acetyl chloride on 2-methyl-3-pheiiylindole magnesium iodide in ether.These authors were able to obtain l-benzoyl-2-benzyl-3-phenylindole (124) but not l-acetyl-2-benzyl-3-phenylindole (125) from 2-benzyl-3-phenylindole magnesium iodide by analogous procedures.3-Acetyl-2-phenylindole (126) and 3-propionyl-2-pheny]indole (127) have recently been prepared in fair yield by the acylation of 2-phenylindole magnesium iodide with acetyl and propionyl chloride, respectively. Le ete obtained a mixture of l-acetyl-3-ethylindole (128) and 2-acetyl-3-ethylindole (129) by the interaction of acetyl chloride with 3-ethylindole magnesium iodide in ether. 

Methylindole is, however, incorporated into mixed dimers and trimers. It thus reacts with indole and with skatole to form mixed dimers, and 2 moles react with 1 mole of indole for form a mixed trimcr. Likewise indole forms a dimer with 1,2-dimethylindole, 2-phenylindole, and even with 2,5-dimethylpyrrole, ... 

Curiously, the ring expansion fails in sulfuric, trifluoroacetic, trichloroacetic, and orthophos-phoric acid. The reaction is sensitive to substituents both in the TV-aryl group and in the 2-and 3-positions of the indole nucleus. For example, 3-methyl-l-phenylindole yields a mixture of 10-methyl-5//-dibenz[/t,/]azepine (34% mp 129-131X) and 2-mcthyl-l-phenylindole (57%). In contrast, 2-methyl-l-phenylindole and 2,3-dimethyl-l-phcnylindole fail to ring expand. The reaction also fails with electron-withdrawing groups (N02 and CF3) in the TV-phenyl ring. 

An important general method of preparing indoles, known as the Fischer Indole synthesis, consists in heating the phenylhydrazone of an aldehyde, ketone or keto-acfd in the presence of a catalyst such as zinc chloride, hydrochloric acid or glacial acetic acid. Thus acetophenone phenylhydrazone (I) gives 2-phenylindole (IV). The synthesis involves an intramolecular condensation with the elimination of ammonia. The following is a plausible mechanism of the reaction ... 

A nickel(II) species is also though to be an intermediate in the carbonyla-tion reaction of iodobenzene with (V-methylbenzaldimine and nickel carbonyl. Two addition modes of an ensuing aroylnickel(II) complex to the C=N double bond can be envisaged as routes to l-methyl-2-phenylindol-3-one and an ethylenediamine derivative (Scheme 47).7 5 The scope of this simple indole synthesis has not been assessed. 

Of all the palladium-catalyzed coupling reactions, the Kumada coupling has been applied least often in indole chemistry. However, this Grignard-Pd cross-coupling methodology has been used to couple l-methyl-2-indolylmagnesium bromide with iodobenzene and a-bromovinyltrimethylsilane to form l-methyl-2-phenylindole and l-methyl-2-(l-trimethyl-... 

The incorporation of an indole ring system often leads to an improvement in the light fastness. A suitable example is Cl Acid Blue 123 (6.177), which is derived from 4,4 -dichlorobenzophenone. Condensation with l-methyl-2-phenylindole in the presence of phosphorus oxychloride produces the triarylmethane ring system. Replacement of the chlorine atoms with p-phenetidine, followed by sulphonation, gives the dye. 

A review of the indoledione-indole rearrangement has appeared. The photoirradiation of l-ethoxy-2-phenylindole in methanol has been shown to afford 3- and 6-ethoxy-2-phenylindoles. ... 

The reaction between A-chlorobenzotriazole and l-methyl-2-phenylindole involves formation of the indole radical cation and benzotriazole radical via an initial electron transfer <82JOC4895, 91JCS(P2)1779>. Chemical reactions of benzotriazole on a freshly etched surface of metallic copper are studied by surface-enhanced Raman scattering, x-ray photoelectron spectroscopy, and cyclic voltammetry. The surface product is (benzotriazolato)copper(-l-), which covers the surface in the shape of polymeric material and shows good anticorrosion effects for copper <91JPC7380>. 

Diels-Alder reaction of indole-2,3-quinodimethanes, 164-169 of pyrrole-2,3-quinodimethanes, 85-87 of vinylindoles, 159 -164 of vinylpyrroles, 79, 84-85 N.N-dihexyl 2-phenylindole-3-acetamide, procedure for. 62... 

Small amounts of 2-phenylisatogen (79a) are formed, together with a number of dimeric indole compounds, as a result of the oxidation of 1-hydroxy-2-phenylindole (78a) with a variety of oxidizing agents (Scheme 6). 

Many early claims of having prepared simple 1-hydroxyindoles have proved to be unfounded, although the unusually stable l-hydroxy-2-phenylindole was obtained in 1895.1-Hydroxyindole itself polymerizes on attempted isolation, while O-acylation, O-alkylation, or the presence of substituents greatly stabilizes the molecule. One 1-hydroxyindole antibiotic has been identified and is the only 1-hydroxyindole derivative isolated from natural sources so far. In contrast, a substantial number of 1-methoxyindoles occurs in various plants, and some of these may inhibit tumor formation in mammals. The biochemistry of these compounds, which include 1-methoxy-indoles, -indolines and -2-oxindoles, has not been widely investigated and could be a very fruitful area for new research which might well lead to novel medicinal agents and other useful compounds. 

Nitration of 2-methyl-3-phenylindole using potassium nitrate in sulfuric acid also yields a mixture of 2-methyl-3-(4-nitropheny )indole (13%) and 2-methyl-5-nitro-3-(4-nitrophenyl)indole (2%). This dinitro product is also obtained by a second nitration of the mononitro compound. However, nitration of 3-methyl-2-phenylindole under these conditions gives only the 5-nitro derivative (80%) with no nitration in the phenyl ring. 

Indole was included with alkyl and arylamines in a study which demonstrated the potential of 2-pyridylsulfonyl as an /v -protecting group. The group is reductively removed using SmI,. <95JOC5969> A possible new means for indole debenzylation was uncovered l-Benzyl-2-phenylindole and several /V-benzylcarbazoles and tetrahydrocarbazoles were found to undergo debenzylation on reaction with methyllithium or LDA. An -elimination mechanism is proposed. <95TL1671>... 

As initially reported by Greci and coworkers83 and later by Greci, Eberson and coworkers84, l-methyl-2-phenylindole (22) treated with A-chlorobenzotriazole (BT-CI, 23) is monochlorinated to 24 and also yields dimeric structures, some of which themselves are chlorinated and dichlorinated (equation 56). Product 27 was mentioned only in the more recent paper. The mechanism in equation 57 was suggested in the initial paper. The formation of products 25-28 was ascribed to the interaction between various substituted indole-radical cations and adventitious water in the medium. The later study confirmed that the substituted indole-radical cation 22a is an intermediate and that the formation of... 

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