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Indoles thallation

Directed thallation has been useful for synthesis of some 4- and 7-substituted indoles. Electrophilic thallation directed by 3-substituents is a potential route to 4-substituled indoles. 3-Formyl[7], 3-acetyi[8] and 3-ethoxycarbonyl[7] groups can all promote 4-thallation. 1-Acetylindoline is the preferred starting... [Pg.139]

The Suzuki coupling of arylboronic acids and aryl halides has proven to be a useful method for preparing C-aryl indoles. The indole can be used either as the halide component or as the boronic acid. 6-Bromo and 7-bromoindolc were coupled with arylboronic acids using Pd(PPh3)4[5]. No protection of the indole NH was necessary. 4-Thallated indoles couple with aryl and vinyl boronic acides in the presence of Pd(OAc)j[6]. Stille coupling between an aryl stannane and a haloindole is another option (Entry 5, Table 14.3). [Pg.143]

Preparation of bromoindoles by replacement of metallic substituents have included oxidation of indolylmagnesium bromide by p-nitrobenzoic acid to give 3-bromoindole (67BSF1294), thallation procedures (illustrated in Scheme 18 also applied to the synthesis of chloroindoles) [85H(23)3113 86H(24)3065 87CPB3146, 87H(26)2817 89H(29)1163], and the use of lithium derivatives. The thallation reactions provide access particularly to 4- and 7-bromoindoles. Quenching the protected 2-lithium derivative of indole with 1,2-dibromotetrachloroethane gave an 87% yield of 2-bromoindole (92JOC2495). [Pg.264]

Snieckus described short syntheses of ungerimine (121) and hippadine by Suzuki couplings of boronic acid 118 with 7-bromo-5-(methylsulfonyloxy)indoline (116) and 7-iodoindoline (117), respectively [130]. Cyclization and aerial oxidation also occur. Treatment of 119 with Red-Al gave ungerimine (121) in 54% yield, and oxidation of 120 with DDQ afforded hippadine in 90% yield. Indoline 116 was readily synthesized from 5-hydroxyindole in 65% overall yield by mesylation, reduction of the indole double bond, and bromination. Indoline 117 was prepared in 67% yield from N-acetylindoline by thallation-iodination and basic hydrolysis. [Pg.100]

Somei and co-workers made extensive use of the Heck reaction with haloindoles in their synthetic approaches to ergot and other alkaloids [26, 40, 41, 240-249]. Thus, 4-bromo-l-carbomethoxyindole (69%) [26], 7-iodoindole (91%) (but not 7-iodoindoline or l-acetyl-7-iodoindoline) [40, 41], and l-acetyl-5-iodoindoline (96%) [41] underwent coupling with methyl acrylate under standard conditions (PdlOAc /PhsP/EtjN/DMF/100 °C) to give the corresponding (E)-indolylacrylates in the yields indicated. The Heck coupling of methyl acrylate with thallated indoles and indolines is productive in some cases [41, 241, 246]. For example, reaction of (3-formylindol-4-yl)thallium bis-trifluoroacetate (186) affords acrylate 219 in excellent yield [241], Similarly, this one-pot thallation-palladation operation from 3-formylindole and methyl vinyl ketone was used to synthesize 4-(3-formylindol-4-yl)-3-buten-2-one (86% yield). [Pg.123]

Somei adapted this chemistry to syntheses of (+)-norchanoclavine-I, ( )-chanoclavine-I, ( )-isochanoclavine-I, ( )-agroclavine, and related indoles [243-245, 248]. Extension of this Heck reaction to 7-iodoindoline and 2-methyl-3-buten-2-ol led to a synthesis of the alkaloid annonidine A [247]. In contrast to the uneventful Heck chemistry of allylic alcohols with 4-haloindoles, reaction of thallated indole 186 with 2-methyl-4-trimethylsilyl-3-butyn-2-ol affords an unusual l-oxa-2-sila-3-cyclopentene indole product [249]. Hegedus was also an early pioneer in exploring Heck reactions of haloindoles [250-252], Thus, reaction of 4-bromo-l-(4-toluenesulfonyl)indole (11) under Heck conditions affords 4-substituted indoles 222 [250], Murakami described the same reaction with ethyl acrylate [83], and 2-iodo-5-(and 7-) azaindoles undergo a Heck reaction with methyl acrylate [19]. [Pg.124]

Prior to his work with internal alkynes, Larock found that o-thallated acetanilide undergoes Pd-catalyzed reactions with vinyl bromide and allyl chloride to give (V-acetylindole and N-acetyl-2-methylindole each in 45% yield [409]. In an extension to reactions of internal alkynes with imines of o-iodoaniline, Larock reported a concise synthesis of isoindolo[2,l-a]indoles 313 and 314 [410]. The regioselectivity was excellent with unsymmetrical alkynes. [Pg.145]

Thallation of l-methoxyindole-3-carbaldehyde with thallium trisfluo-roacetate followed by treatment with potassium iodide gave the 4-iodo derivative in 91% yield, and this has been converted into many other 1-methoxyindole derivatives (86CPB677). When the thallated indole reacted with methyl acrylate in the presence of a catalytic quantity of pal-ladium(ll) acetate, 47% of the product was the 4-derivative 160, but 11% of the 5-isomer was also formed (86CPB4116). [Pg.139]

Some effected the coupling of phenyl-, 2-fuiyl-. and 1-hexenylboronic acids with 4-thallated indole-3-carboxaldehyde (Pd(OAc),/DMF) to give 4-substituted 3-formylin-doles [148]. Regioselective thallation of indole-3-carboxaldehyde is achieved using thallium tris-trifluoroacetate in 77% yield. Indole 129, which is available by the Buchwald zirconium indoline synthesis, was used by Buchwald to synthesize 130 via a Suzuki protocol [149]. Boronate ester 130 is prepared by the hydroboration of3-methyl-1-butyne with catechol borane. Indole 131 had been used in earlier studies to synthesize the clavicipitic acids. [Pg.108]

Thallation of benzanilides with thallium tris(trifluoroacetate) in a mixture of trifluoroacetic acid and ether gave the c rr/to-thallated products. Reaction of these products with copper(I) acetylide in acetonitrile led to the 2-benzamidotolanes (119), which were eventually elaborated into the 2-phenyl-indole derivatives. 111 ... [Pg.275]

Indolines are useful intermediates for the synthesis of indoles with substituents in the carbocyclic ring. In electrophilic substitutions, they behave like anilines the example shows iV-acetylindoline undergoing regioselective 7-thallation. Nitration of indoline 2-carboxylic acid gives the 6-nitro-derivative separation... [Pg.415]

Thallation of 3-acyl indoles gives the 4-thallated products, which can be converted to both the 4-nitro and 4-azido derivatives in copper(II)-promoted processes <89H(29)643>. The nitro compound is formed by heating the organothallium intermediate with sodium nitrite and copper sulfate in DMF at 100°C. This methodology has been used in a total synthesis of indolactam-V <90T6623>. [Pg.43]

Synthesis of indoles via 2,3-dihydroindoles (indolines) is sometimes done in order to achieve a specific substitution pattern in the carbocyclic ring <67RCR753>. Indolines, being aniline derivatives, readily undergo electrophilic substitution at C5. Indolines can also be used to achieve selective 7-substitution. The 1-Boc derivative of indoline can be lithiated at C7 <92H(34)i03i> and 1-acetyl-indoline is thallated at C7 <89H(29)643>. These organometallic intermediates can be functionalized and then aromatized to indoles. There are a number of methods which have been developed for oxidative aromatization of dihydroindoles. Table 3 cites some examples. [Pg.157]

Regioselective thallation (see Section 2.03.4.2) can be used to introduce halogen at C4 or C7 of the indole ring. For example, 5,7 and 6,7-dibromoindole-3-carboxaldehyde can be converted to the corresponding 4-bromo derivative by reaction with T1(02CCF3)3 and CuBrj <89H(29)1663>. [Pg.176]


See other pages where Indoles thallation is mentioned: [Pg.259]    [Pg.182]    [Pg.571]    [Pg.259]    [Pg.182]    [Pg.571]    [Pg.159]    [Pg.101]    [Pg.113]    [Pg.119]    [Pg.217]    [Pg.278]    [Pg.284]    [Pg.287]    [Pg.289]    [Pg.335]    [Pg.335]    [Pg.159]    [Pg.119]    [Pg.124]    [Pg.129]    [Pg.129]    [Pg.270]    [Pg.271]    [Pg.206]    [Pg.335]    [Pg.43]   
See also in sourсe #XX -- [ Pg.315 ]




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Indole-3-carbaldehyde thallation

Thallate

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