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Oxidative cyclization intramolecular

Phenol, Oms-2-(2-butenyl)-asymmetric intramolecular oxidative cyclization, 6,365 Phenol, 4-cyano-hydrolysis... [Pg.192]

Isoxazole derivatives have also been synthesized in variable yield by the palladium-catalyzed intramolecular oxidative cyclization of a,/i-unsaturated oximes (Scheme 110).174 Reactions of this type are reminiscent of procedures... [Pg.368]

SN]-Labeled 4,6-dimethyl-47/-[l,2,5]oxadiazolo[3,4-rf pyrimidine-5,7-dione 1-oxide 290 is conveniently prepared by nitration of commercially available 6-amino-l,3-dimethyl-l//-pyrimidine-2,4-dione using 15N-enriched nitric acid followed by an intramolecular oxidative cyclization with iodosylbenzene diacetate under mild conditions <2000JOC6670>. [Pg.373]

Katritzky developed a facile synthesis of l,2-diaryl(heteroaryl)pyrroles in a two-step procedure from A-allylbenzotriazoles via intramolecular oxidative cyclization in the presence of a Pd(II) catalyst <00JOC8074>. Thus, treating A-allylbenzotriazole (21) with n-butyllithium followed by addition of a diarylimine yielded the (2-benzotriazolyl-l-arylbut-3-en)anilines 22 which were subsequently heated in the presence of the system Pd(OAc)2-PPh3-CUCI2-K2CO3 to undergo intermolecular amination with simultaneous oxidation of the intermediate 3-pyrroline to the pyrroles 23. [Pg.113]

Our final conclusion was therefore that the mechanism of intramolecular oxidative cyclization of 1,3,5-triphenylformazan to 2,3,5-triphenyltetrazolium perchlorate involves cyclization of the initial radical cation and deprotonation as the rate-determining step, following the mechanistic scheme e-c-P-e. [Pg.92]

Akermark et al. reported the palladium(II)-mediated intramolecular oxidative cyclization of diphenylamines 567 to carbazoles 568 (355). Many substituents are tolerated in this oxidative cyclization, which represents the best procedure for the cyclization of the diphenylamines to carbazole derivatives. However, stoichiometric amounts of palladium(II) acetate are required for the cyclization of diphenylamines containing electron-releasing or moderately electron-attracting substituents. For the cyclization of diphenylamines containing electron-attracting substituents an over-stoichiometric amount of palladium(II) acetate is required. Moreover, the cyclization is catalyzed by TFA or methanesulfonic acid (355). We demonstrated that this reaction becomes catalytic with palladium through a reoxidation of palladium(O) to palladium(II) using cupric acetate (10,544—547). Since then, several alternative palladium-catalyzed carbazole constructions have been reported (548-556) (Scheme 5.23). [Pg.206]

The intramolecular oxidative cyclization of the anilinobenzoquinone 940 with a catalytic amount of palladium(II) acetate in the presence of copper(II) acetate in air afforded the carbazole-l,4-quinone 941 in almost quantitative yield. The regioselective introduction of the heptyl side chain at C-1 of the carbazole-l,4-quinone 941 was achieved by a 1,2-addition of the corresponding Grignard reagent to give the carbazole-l,4-quinol 942 in 55% yield. However, 1,4-addition at C-3 and 1,2-addition at C-4 led to the regioisomeric products 943 and 944 as well. Finally, under acidic reaction conditions, the carbazole-l,4-quinol 942 was smoothly transformed to... [Pg.272]

Not unrelated to the above syntheses is the intramolecular oxidative cyclization of ubiquinone (108) to ubichromenol (110) (63JA239). Catalyzed by bases, of which pyridine seems to be the choice example (65JCS5060), the reaction proceeds through the o-quinoneallide (109). Significantly, this process is also-brought about by irradiation with visible light <65LA(684)212>. [Pg.752]

In fact, the role of copper and oxygen in the Wacker Process is certainly more complicated than indicated in equations (151) and (152) and in Scheme 10, and could be similar to that previously discussed for the rhodium/copper-catalyzed ketonization of terminal alkenes. Hosokawa and coworkers have recently studied the Wacker-type asymmetric intramolecular oxidative cyclization of irons-2-(2-butenyl)phenol (132) by 02 in the presence of (+)-(3,2,10-i -pinene)palladium(II) acetate (133) and Cu(OAc)2 (equation 156).413 It has been shown that the chiral pinanyl ligand is retained by palladium throughout the reaction, and therefore it is suggested that the active catalyst consists of copper and palladium linked by an acetate bridge. The role of copper would be to act as an oxygen carrier capable of rapidly reoxidizing palladium hydride into a hydroperoxide species (equation 157).413 Such a process is also likely to occur in the palladium-catalyzed acetoxylation of alkenes (see Section 61.3.4.3). [Pg.365]

Intramolecular oxidative cyclizations in the appropriately substituted phenols and phenol ethers provide a powerful tool for the construction of various practically important polycyclic systems. Especially interesting and synthetically useful is the oxidation of the p-substituted phenols 12 with [bis(acyloxy)iodo]-arenes in the presence of an appropriate external or internal nucleophile (Nu) leading to the respective spiro dienones 15 according to Scheme 6. It is assumed that this reaction proceeds via concerted addition-elimination in the intermediate product 13, or via phenoxenium ions 14 [18 - 21]. The recently reported lack of chirality induction in the phenolic oxidation in the presence of dibenzoyltar-taric acid supports the hypothesis that of mechanism proceeding via phenoxenium ions 14 [18]. The o-substituted phenols can be oxidized similarly with the formation of the respective 2,4-cyclohexadienone derivatives. [Pg.103]

Wang and colleagues found that 10 mol% of FeCl3 catalyzed the intramolecular oxidative cyclization of acceptor-substituted ( )- and (Z)-stilbenes 93 to... [Pg.220]

Tab. 2. Substituent effects on the PIFA-mediated intramolecular oxidative cyclization of a,co-biaryls. Tab. 2. Substituent effects on the PIFA-mediated intramolecular oxidative cyclization of a,co-biaryls.
A series of dibenzofuran-l,4-diones illustrated in the following scheme were constructed via a DDQ-mediated intramolecular oxidative cyclization of quinone-arenols <070L2807>. Dibenzo[b] furans were also found to be made from 2//-pyran-2-ones and 6,7-dihydro-577-benzo[Z>]furan-4-one <07T1610>. The asymmetric synthesis of chiral furo-fused BINOL derivatives was achieved via copper(II)-mediated oxidative coupling from naphthofuranol in the presence of chiral phenylethylamine <07TL317>. [Pg.177]

Scheme 26 Pd-catalyzed intramolecular oxidative cyclization of bisindolylmaleimides... Scheme 26 Pd-catalyzed intramolecular oxidative cyclization of bisindolylmaleimides...
Scheme 29 Pd(II)-catalyzed intramolecular oxidative cyclization for the synthesis of carbazoles O... Scheme 29 Pd(II)-catalyzed intramolecular oxidative cyclization for the synthesis of carbazoles O...
After exploring intermolecular reactions, White and coworkers utilized complex Ll/Pd11 to catalyze the intramolecular oxidative cyclization of 4 to synthesize the macrolide 5 with moderate yield and good regioselectivity (Scheme 7) [23]. Further studies on substrate scope demonstrated that this catalytic system was compatible with various carboxylic acids as nucleophiles, such as aryl acids, vinylic and alkyl acids, leading to the generation of 14- to 19-membered macrolides with remarkable levels of selectivity. [Pg.199]

A rhodium(III) catalyst was also shown by Witulski and Schweikert to promote the intramolecular oxidative cyclization of bisindolylmaleimides to indolocarbazoles as a key step in the synthesis of cytotoxic agents of the... [Pg.268]

A variation of the oxidative cyclization of aryl thioureas has been reported to yield aminobenzothiazoles. Based on this approach, Martinez et al. have described a facile and versatile approach to cyclize Af-alkyl, iV -aryl, or heteroaryl thioureas via intramolecular oxidative cyclization in the presence of sulfuryl chloride in dichloromethane. °°... [Pg.317]

Chemo- and regioselective synthesis of naphtho[2,3-c]chromenes result from the palladium-catalyzed reaction of 2-haloaryl aUenes with 2-alkynyl-phenols in refluxing 1,4-dioxane (Scheme 18) (14CC5891). Another palladium catalyst was involved in the intramolecular oxidative cyclization of 3-allyl-2 -hydroxyflavones to afford chromone[2,3-c]-2f/-chromenes in good... [Pg.478]

A convenient and stereoselective, synthetic route was reported for the preparation of 3,7-disubstituted-l,2,5-trithiepanes 209 by the reaction of thiiranes with bis(trimethylsilyl)sulfide (HMDST) followed by intramolecular oxidative cyclization (14HAC678). In the reaction of substituted etha-nolamines with formaldehyde, the desired bis(oxazolidin-3-yl)methanes were prepared as a mixture of products, the ratio of the isomeric 3,8-dioxa-l,6-diazabicyclo[4.4.1]undecane 210 product present was dependent on the substituent on the ethanolamine (14CHE726). Whether the bis(oxazolidin-3-yl)methanes were isolated or the mixtures were taken on for further reaction, the subsequent product was formed exclusively. [Pg.562]

Examples of intramolecular oxidative cyclizations promoted by Cu(OTf)2 include cyclization of enolates of diketones and diesters (eq 4) and oxidative cyclization of hydrolytically resistant, s-and ,( -unsaturated silyl enol ethers." For instance, (1) reacts with excess Cu20/Cu(0Tf)2 in MeCN to give a 90% yield of a 20 1 mixture of the trans-fused and cis-fused tricyclic ketones (2) and OHeqS)." ... [Pg.182]

The hypervalent iodine reagent PhI(OTf)2 (generated in situ) promotes the metal-free oxidative production of C-O bonds, through an intramolecular oxidative cyclization of substituted N-styrylbenzamides 131 to give oxazoles 132 (13SL2119). [Pg.334]

Extraordinarily large apical fcp couplings have been observed by Kobayashi and Kawashima " in the spectra of 5-carbaphosphatranes obtained by the reaction of l-hydro-5-carbaphosphatrane with nucleophiles and subsequent intramolecular oxidative cyclization. [Pg.208]

Arylbenzothiazoles are obtained by intramolecular oxidative cyclization of N-arylthioamides 9 ... [Pg.210]

Trifluoromethylaled thiobenzanilides are converted efficiently to 2-triflnoromelliylbenzothiazoles via intramolecular oxidative cyclization under CAN/NaHCOs oxidation [104]. The optimized reaction conditions were also evaluated for a range of substituted precursors in the presence of 5 mol % PdC [57],... [Pg.451]


See other pages where Oxidative cyclization intramolecular is mentioned: [Pg.98]    [Pg.159]    [Pg.180]    [Pg.218]    [Pg.22]    [Pg.56]    [Pg.776]    [Pg.252]    [Pg.776]    [Pg.461]    [Pg.470]    [Pg.159]    [Pg.184]    [Pg.139]    [Pg.7208]    [Pg.169]   
See also in sourсe #XX -- [ Pg.390 ]

See also in sourсe #XX -- [ Pg.173 , Pg.470 ]

See also in sourсe #XX -- [ Pg.317 ]




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Oxidation intramolecular

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