Indole 2-ethyl

One route to o-nitrobenzyl ketones is by acylation of carbon nucleophiles by o-nitrophenylacetyl chloride. This reaction has been applied to such nucleophiles as diethyl malonatc[l], methyl acetoacetate[2], Meldrum s acid[3] and enamines[4]. The procedure given below for ethyl indole-2-acetate is a good example of this methodology. Acylation of u-nitrobenzyl anions, as illustrated by the reaction with diethyl oxalate in the classic Reissert procedure for preparing indolc-2-carboxylate esters[5], is another route to o-nitrobenzyl ketones. The o-nitrophenyl enamines generated in the first step of the Leimgruber-Batcho synthesis (see Section 2.1) are also potential substrates for C-acylation[6,7], Deformylation and reduction leads to 2-sub-stituted indoles. 

Ethyl indole-2-carboxylate 3-(Methoxycarbonyl)propanoyl chloride, AICI3, nitrobenzene 95 [10]... 

Ethyl indole-2-carboxylate 4-Methoxybenzoic acid, TFAA, H3PO4 74 [11]... 

X)ml), The reaction mixture was stirred for 24 h. Nearly all of the solvent was removed in vacuo and the residue dissolved in CH2CI2. The solution was washed with 5% NHj, 1N HCl and brine. The organic layer was dried (NajSOJ and the solvent evaporated in vacuo. The residue was purified by chromatography using CHClj-hexane to give the product (28.0 g, 86%) along with a little 3-[2-nitro-2-(indol-3-ylmethyl)ethyl]indole (2.8 g. 5%). 

A traditional method for such reductions involves the use of a reducing metal such as zinc or tin in acidic solution. Examples are the procedures for preparing l,2,3,4-tetrahydrocarbazole[l] or ethyl 2,3-dihydroindole-2-carbox-ylate[2] (Entry 3, Table 15.1), Reduction can also be carried out with acid-stable hydride donors such as acetoxyborane[4] or NaBHjCN in TFA[5] or HOAc[6]. Borane is an effective reductant of the indole ring when it can complex with a dialkylamino substituent in such a way that it can be delivered intramolecularly[7]. Both NaBH -HOAc and NaBHjCN-HOAc can lead to N-ethylation as well as reduction[8]. This reaction can be prevented by the use of NaBHjCN with temperature control. At 20"C only reduction occurs, but if the temperature is raised to 50°C N-ethylation occurs[9]. Silanes cun also be used as hydride donors under acidic conditions[10]. Even indoles with EW substituents, such as ethyl indole-2-carboxylate, can be reduced[ll,l2]. 

Ethyl indole-2-carboxylate (45.2 g, 0.238 mmol) was dissolved in abs. EtOH (450 ml) in a 11 polyethylene container and cooled in a dry icc-cthanol bath. The solution was saturated with dry HCl gas until the volume increased to 875 ml, Granular tin metal (84.2g, 0.7l0mmol) was added to the slurry and... 

The arylhydrazone 24 generally gives the 3-alkyl-2-methylindole 25 as major product. However, the indolization of ethyl methyl ketone has been reported to provide both 2,3-dimethyl indole and 2-ethyl indole. " ... 

R" = CH20H). The use of sodium borohydride in place of lithium aluminum hydride did not lead to ring closure but to 3-[j8-(A-l,2,3,4-tetrahydroisoquinolyl)ethyl]indole derivatives (53). Reductive cyclization by means of lithium aluminum hydride of the j8-(3-indolyl)ethyl-l-isoquinoline (52) to the pentacyclic tetrahydro-j8-carboline 49 (R = R = R" = H) has been reported. Strong acid alone sufficed to convert 52 into 54, the 0x0 derivative of 49. ... 

Treatment of the benzodiazepine 3 with hydrogen chloride in methanol gives ethyl indole-1-carboxylate (6) via the isolable intermediates 4 and 5.164... 

ETHYL INDOLE-2-C ARBO XYLATE (Indole-2-carboxylic acid, ethyl ester)... 

The dried ester can be further purified by treatment with charcoal and recrystallization from a mixture of methylene chloride and light petroleum ether (b.p. 60-68°). This gives 11.3-11.7 g. (41-44% based on o-nitrotoluene) of ethyl indole-2-carboxylate in the form of white needles, m.p. 122.5-124° (Note 5). 

Alkaline hydrolysis of ethyl indole-2-carboxylate yields indole-... 

Ethyl indole-2-carboxylate, 43,40 Ethyl isocyanide, 41, 15 N-Ethyi-N-methylaniline, 43,47 Ethyl o-nitrophenylpyruvate, potassium salt of, 43, 40... 

Reductive cyclization of the potassium salt of ethyl o-nitrophenylpyru-vate to ethyl indole-2-carboxyl-ate, 43, 40... 

A semisystematic study into the hydrolysis of ethyl indole-2-carboxylate in aqueous media at high temperature, indicated that decarboxylation of the resultant acid proceeded by an arenium ion mechanism and was inhibited by base. As base pro-... 

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>. 

An improved procedure for the synthesis of octahydroindoloquinolizine (1) from 3-(2-piperidino-ethyl)indole by oxidative cyclization process has been reported (392). 

Moody and Rahimtoola reported a short synthesis of staurosporinone (293) without the use of protecting groups at the indole or the lactam nitrogen (761,762). This route involves an intramolecular Diels-Alder reaction of the pyrano[4,3- 7]indol-3-one 1325 and a subsequent cyclization by nitrene insertion. The pyrano[4,3-l7]indol-3-one 1325 was obtained in four steps from ethyl indol-2-yl... 

Die intramolekulare Photooxidation unter Beteiligung einer aliphatischen Nitro-Gruppe fuhrt bei Bestrahlung von 3-(2-Ethoxyearbonyl-2-nitro-ethyl)-indol in Acetonitril in be-friedigender Ausbeute zur Oxidation des Indolgerustes4 ... 

Mit Tryptamin in Benzol/Tetrahydrofuran (1 1) erhalt man analog 3-[2-(4-Acetoxyme-thyl-2-cyclohexen-l-ylamino)-ethyl]-indol. 

TRYPTAMINE, N,N-DIBUTYL INDOLE, 3-[2-(DIBUTYLAMINO)ETHYL] N,N-DIBUTYLTRYPTAMINE 3-[2-(DIBUTYLAMINO)ETHYL]INDOLE... 

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