共查询到20条相似文献,搜索用时 0 毫秒
1.
The synthesis of 3,4,5-trisubstituted pyrazoles via a tandem catalytic cross-coupling/electrocyclization of enol triflates and diazoacetates is presented. The initial scope of this methodology is demonstrated on a range of differentially substituted acyclic and cyclic enol triflates as well as an elaborated set of diazoacetates to provide the corresponding pyrazoles with a high degree of structural complexity. 相似文献
2.
A norbornene-mediated palladium-catalyzed sequence is described in which two alkyl-aryl bonds and one alkenyl-aryl bond are formed in one pot with use of microwave irradiation. A variety of symmetrical and unsymmetrical oxygen-, nitrogen-, silicon-, and sulfur-containing tricyclic heterocycles were synthesized from a Heck acceptor and an aryl iodide containing two tethered alkyl halides. This approach was further applied to the synthesis of a tricyclic mescaline analogue. 相似文献
3.
4.
[reaction: see text] The thionium ion, generated through a cyclopropylcarbinyl-cyclobutyl ring expansion, is, for the first time, intramolecularly intercepted by activated aromatic rings to generate new versatile 2a-methyl-8b-(phenylsulfanyl-1,2a,3,8b-tetrahydro-2H-cyclobuta[c]chromenes. 相似文献
5.
6.
Klapars A Parris S Anderson KW Buchwald SL 《Journal of the American Chemical Society》2004,126(11):3529-3533
A simple method for the preparation of medium ring heterocycles (7-, 8-, 9-, and 10-membered) has been developed. The process employs a Cu-catalyzed coupling of a beta-lactam with an aryl bromide or iodide followed by intramolecular attack of a pendant amino group. In some instances, the intermediate beta-lactam is observable but can be converted to the aza-heterocycle by catalysis. Acetic acid was found to be superior to transition metal complexes as a catalyst for this ring-expansion process. 相似文献
7.
Ihsan UllahMuhammad Nawaz Alexander VillingerPeter Langer 《Tetrahedron letters》2011,52(16):1888-1890
Fluoranthenes were prepared by domino two-fold Heck/electrocyclization/dehydrogenation reactions of 1,2-dibromoacenaphthylene. 相似文献
8.
The total synthesis of oxacalothrixins, an isostere of biologically important carbazoloquinone alkaloid, calothrixin B was achieved from 2-acetyl-3-methylbenzofuran. An iodine/TBHP-mediated oxidative cyclization of benzofuranyl-enamine has been employed as a key step to synthesize, the crucial intermediate 1-hydroxy dibenzofurancarbaldehyde. The latter upon reductive cyclization followed by PIDA-mediated oxidation furnished oxacalothrixin B and its analogues. 相似文献
9.
10.
Treatment of 1 equiv of 1,3-bis(bromomethyl)benzene and 2,6-bis(bromomethyl)pyridine with 1 equiv of indole in the presence of NaH in THF afforded the symmetrical cyclophanes 1 and 2. Using similar methodology, cylindrical cyclophanes 3 and 4 were obtained from 2 equiv of 1,3,5-trimethyl-2,4,6-tris(bromomethyl)benzene and 1,3,5-tris(bromomethyl)benzene with 3 equiv of indole. 相似文献
11.
A series of five- to eight-membered nitrogen-containing heterocycles were prepared via a general and efficient one-pot, two-component sequence featuring rhodium-catalyzed insertion of a vinyl-substituted α-diazocarbonyls into the N-H bond of a series of tert-butoxycarbonyl-(Boc)-protected amines, followed by ring-closing metathesis catalyzed by ruthenium benzylidene complexes. This methodology allows easy and convenient access to highly functionalized azacycloalkenes in moderate yields and excellent chemoselectivity in a single transformation. 相似文献
12.
V. P. Semenov A. N. Studenikov A. A. Potekhin 《Chemistry of Heterocyclic Compounds》1978,14(3):233-245
The literature data on the synthesis of pyrroles, indoles, carbazoles, and other condensed systems containing a pyrrole ring and on their hydrogenated derivatives by means of nitrenes and potential precursors of the latter are correlated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 291–305, March, 1978. 相似文献
13.
14.
V. P. Semenov A. N. Studenikov A. A. Potekhin 《Chemistry of Heterocyclic Compounds》1979,15(5):467-483
The intramolecular cyclization of heteroanalogs of 1,3-butadien-1-ylnitrenes, the expansion and contraction of the rings of hetarylnitrenes, the incorporation of nitrenes, and the intermolecular dipolar cycloaddition of acylnitrenes to unsaturated compounds, which leads to the formation of five-membered nitrogen heterocycles with several heteroatoms, are examined.See [1] for Part I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 579–598, May, 1979. 相似文献
15.
[reaction: see text] The application of easily accessed propargyl vinyl ethers for the synthesis of monocyclic 2H-pyrans was achieved. Under the reaction conditions, highly substituted heterocycles were obtained in moderate to excellent yields. The one-pot sequence proceeds via a Ag(I)-catalyzed propargyl-Claisen rearrangement, followed by a base-catalyzed isomerization, and 6pi-oxaelectrocyclization, leading to the formation of stable 2H-pyrans. 相似文献
16.
A new method for the preparation of 2-amino-4(3H)-quinazolinones and similar fused heterocycles is described. Simply warming a mixture of an aryl guanidine and carbonyl diimidazole in acetonitrile results in formation of a putative N-amidinoisocyanate intermediate which undergoes a 6π-electron electrocyclic reaction with the aryl ring to generate the quinazolinone ring system. The mild conditions are compatible with a variety of functional groups, and the reaction is shown to be successful on multigram scale. 相似文献
17.
A two-stage "tandem strategy" for the synthesis of benzofused nitrogen heterocycles is described that is particularly useful for the construction of systems with a high level of substitution on the benzenoid ring. The first stage in the strategy involves a benzannulation based on the reaction of cyclobutenones with ynamides. This cascade process proceeds via a sequence of four pericyclic reactions and furnishes a multiply substituted aniline derivative which can bear a variety of functionalized substituents at the position ortho to the nitrogen. In the second stage of the tandem strategy, ring-closing metathesis generates the nitrogen heterocyclic ring. This two-step sequence provides efficient access to highly substituted dihydroquinolines, benzazepines, benzazocines, and related benzofused nitrogen heterocyclic systems. The application of this chemistry in a concise formal total synthesis of the anticancer agents (+)-FR900482 and (+)-FR66979 is described. 相似文献
18.
The regioselective Heck arylation of unsaturated alcohols is utilized as the key step in a convenient one-pot procedure for the production of 2,2-disubstituted tetrahydrofurans and tetrahydropyrans. The arylation reaction is effected with a palladium-diphosphine catalyst alongside a hydrogen bond donor; this is followed by the introduction of a Br?nsted acid to the reaction mixture, affording the oxygen heterocycles in moderate yields. 相似文献
19.
A generalised scheme for the synthesis of flavones, flavonones and chromones involving 3-acyl-γ-pyrone intermediates has been developed. Convenient synthesis of other oxygen heterocycles using similar procedure have been outlined. 相似文献
20.
Holber Zuleta-Prada 《Tetrahedron letters》2009,50(38):5336-8147
In the present work, a novel stereoselective radical cyclization/oxidation/spirocyclization cascade process using a mixture of n-Bu3SnH/ dilauroyl peroxide is described. The proposed mechanism for this later process combines a 6-endo cyclization of an aryl radical onto an enamide double bond, and a consecutive oxidative-ionic spirocyclization at C-3 of an indole nucleus. All processes led to the construction of new spiroindolenine derivatives in a one-step synthesis starting from relatively simple starting materials. The organic peroxide appears to act as the initiator and the oxidant. 相似文献