共查询到20条相似文献,搜索用时 15 毫秒
1.
An efficient protocol for palladium-catalyzed direct C-3 arylation of indoles containing unprotected heterocyclic nitrogen atom has been developed. 相似文献
2.
A highly enantioselective palladium-catalyzed carbozincation of cyclopropenes has been developed. The intermediate cyclopropylzinc species, after transmetalation with copper, were trapped with various electrophiles. This one-pot procedure furnished functionalizied cyclopropenes with excellent diastereo- and enantioselectivity. 相似文献
3.
A novel approach towards 7b-aryl-indeno[1,2,3-jk]fluorene based on a nitrogen-containing core is reported. The acid-promoted Friedel-Crafts reaction of 9-(2-bromophenyl)-9-fluorenol with carbazole, triphenylamine or triindole afforded 9-(2-bromophenyl)fluorenyl-carbazole, -triphenylamine and -triindole derivatives, which were subsequently converted to 7b-aryl-fluoradenes via palladium-catalyzed intramolecular C-H direct arylation as a key step. 相似文献
4.
We present a new, practical method by which N-substituted indoles may be selectively arylated in the C2-position with good yields, low catalyst loadings, and a high degree of functional group tolerance. Our investigation found that two competitive processes, namely, the desired cross-coupling and biphenyl formation, were operative in this reaction. A simple kinetic model was formulated that proved to be instructive and provided useful guidelines for reaction optimization; the approach described within may prove to be useful in other catalytic cross-coupling processes. 相似文献
5.
McClure MS Glover B McSorley E Millar A Osterhout MH Roschangar F 《Organic letters》2001,3(11):1677-1680
An efficient regioselective method for the direct arylation of 2-furaldehyde to provide a range of pi-diverse 5-aryl-2-formylfuran derivatives is described. The method employs functionalized aryl halides and a catalytic amount of palladium(II) chloride under relatively mild conditions. 相似文献
6.
A highly regioselective Pd-catalyzed arylation of N-methylpyrazoles with aryl bromides is described. This transformation was studied extensively via automated reaction screening. A Design of Experiments (DoE) approach for optimizing the critical parameters was applied, resulting in excellent conditions for preparing selectively 5-arylpyrazoles in moderate to excellent yields under mild conditions. 相似文献
7.
A catalyst generated from Pd(OAc)2 and dppp is effective for the direct intramolecular arylation of alkenyl triflates. Conjugated alkene-arene-containing carbocycles are produced in good yield. The process tolerates a variety of aryl substituents as well a simple heteroaryl groups. Electron-deficient aryl rings deliver faster reactions. 相似文献
8.
The arylation reaction of carbanions, derived from certain sulfones, cyanoacetic ester and malononitrile, with aryl bromides (using the catalytic system of Pd2dba3/3L, L=PPh3, PtBu3) as well as the reaction of the carbanions with one equivalent of 4-CF3C6H4 Pd(PPh3)2Br has been studied. These reactions proceed smoothly provided that the base stronger than the initial carbanion is present in the reaction mixture. In the absence of the above type of base the reactions do not proceed at all. Taking that into account we have proposed a novel mechanism of palladium-catalyzed arylation of CH-acids. The main feature of this mechanism is the accelaration of the reductive elimination due to the deprotonation of the intermediate ArPdL2CHXY. The correlation between the carbanion reactivity and the pKa values for related CH-acids as well as the ligand effect are discussed in the framework of the proposed mechanism. 相似文献
9.
[Structure: see text] Palladium-catalyzed arylation of sulfenate anions generated from beta-sulfinyl esters can take place under biphasic conditions. This hitherto unknown reaction provides a simple, mild, and efficient route to aryl sulfoxides in good yields. The development of a new pseudo-domino type I procedure involving a sulfinylation followed by a Mirozoki-Heck coupling is also described. 相似文献
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11.
Lesbani A Kondo H Yabusaki Y Nakai M Yamanoi Y Nishihara H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(45):13519-13527
A convenient procedure has been developed for the preparation of Group 14 compounds by integrated palladium-catalyzed cross-coupling of aromatic iodides with the corresponding Group 14 hydrides in the presence of a base. The reaction conditions can be applied to the cross-coupling of tertiary, secondary, and primary Group 14 compounds. In most cases, the desired arylated products were obtained in synthetically useful yields. Even in the case of aryl iodides containing OH, NH(2), CN, or CO(2)R groups, the reactions proceeded with good to high yields with tolerance of these reactive functional groups. A possible application of this method is the unique synthesis of a fungicidal diarylmethyl(1H-1,2,4-triazol-1-ylmethyl)silane derivative. 相似文献
12.
We have recently developed palladium-catalyzed methods for direct arylation of indoles (and other azoles) wherein high C-2 selectivity was observed for both free (NH)-indole and (NR)-indole. To provide a rationale for the observed selectivity ("nonelectrophilic" regioselectivity), mechanistic studies were conducted, using the phenylation of 1-methylindole as a model system. The reaction order was determined for iodobenzene (zero order), indole (first order), and the catalyst (first order). These kinetic studies, together with the Hammett plot, provided a strong support for the electrophilic palladation pathway. In addition, the kinetic isotope effect (KIE(H/D)) was determined for both C-2 and C-3 positions. A surprisingly large value of 1.6 was found for the C-3 position where the substitution does not occur (secondary KIE), while a smaller value of 1.2 was found at C-2 (apparent primary KIE). On the basis of these findings, a mechanistic interpretation is presented that features an electrophilic palladation of indole, accompanied by a 1,2-migration of an intermediate palladium species. This paradigm was used to design new catalytic conditions for the C-3 arylation of indole. In case of free (NH)-indole, regioselectivity of the arylation reaction (C-2 versus C-3) was achieved by the choice of magnesium base. 相似文献
13.
García-Cuadrado D Braga AA Maseras F Echavarren AM 《Journal of the American Chemical Society》2006,128(4):1066-1067
Under the usual conditions, the Pd-catalyzed arylation does not involve an electrophilic aromatic substitution reaction. On the basis of DFT calculations, we propose a mechanism for the Pd-catalyzed arylation that involves a proton abstraction by a carbonate or related ligand and that provides a satisfactory explanation for the experimental data. 相似文献
14.
Marc Lafrance 《Tetrahedron》2008,64(26):6015-6020
The influence of ligand, stoichiometric base, and additive has been evaluated in the context of intramolecular direct arylation reactions. Under the optimal conditions, arylation of simple arenes can be performed under very mild conditions, with heating to 50 °C. The role of the pivalic acid additive is rationalized by invoking a concerted palladation-deprotonation pathway where the pivalate is behaving as either an intramolecular base from the palladium metal or through an intermolecular deprotonation in a similar manner as that previously described by Echavarren and Maseras. 相似文献
15.
A new method for the efficient, practical, and highly regioselective direct palladium-catalyzed C-3 arylation of free (NH)-indole and its electron-rich 1-unsubstituted derivatives under ligandless conditions is described. The reactions, which are run outside a glovebox without purification of solvent and reagents, involve treatment of free (NH)-indoles with activated, unactivated, and deactivated aryl bromides in refluxing toluene in the presence of K2CO3 as the base and a catalyst system consisting of a combination of Pd(OAc)2 and benzyl(tributyl)ammonium chloride. The experimental results are consistent with a catalytic cycle based on an electrophilic palladation pathway at the 3-position of 1-indolyl potassium salts. 相似文献
16.
[reaction: see text] The regioselective palladium(0)-catalyzed arylation of 3-furoate and 3-thiophenecarboxylate esters with aryl bromides is described. Conditions were developed that allow for the selective synthesis of either 2-aryl or 5-aryl products. 相似文献
17.
The ortho arylation of anilides to form biphenyls via a twofold C-H functionalization/C-C bond-forming process is described. The oxidative coupling takes place in the presence of 5-10 mol % of Pd(OAc)2, 10-20 mol % of DMSO, and 4-11 equiv of the aryl substrate in TFA under an oxygen atmosphere. No metal-containing cocatalyst is required. 相似文献
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19.
Harry R. Chobanian Ping Liu Marc D. Chioda Yan Guo Linus S. Lin 《Tetrahedron letters》2007,48(7):1213-1216
We report an expedient method for the heteroarylation of acetone under tin-free conditions. The coupling is performed using the commercially available enol silane of acetone (2-trimethylsilyloxypropene) and a corresponding aryl bromide, chloride or triflate under microwave-assisted conditions, with tris(dibenzylideneacetone)dipalladium (Pd2(dba)3) or palladium acetate (Pd(OAc)2) and 2-(2′,6′-dimethoxybiphenyl)dicyclohexylphosphine (S-Phos) as the catalyst system. 相似文献
20.
Kamikawa K Takemoto I Takemoto S Matsuzaka H 《The Journal of organic chemistry》2007,72(19):7406-7408
[5]- and [6]helicenes were synthesized in moderate to good yields from Z,Z-bis(bromostilbene)s by palladium-catalyzed double C-H arylation reaction. This method can be applied to the syntheses of helicenes possessing electron-deficient substituents. 相似文献