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1.
An efficient total synthesis of rhein and diacerhein has been accomplished by relying on a remarkable regioselective directed ortho metalation (DOM) followed by a one-pot two step addition-cyclization reaction, generating phthalide 5 intermediate efficiently. 相似文献
2.
Hemaka A. Rajapakse Mary Beth Young Samantha Charlton Nancy N. Tsou 《Tetrahedron letters》2005,46(51):8909-8912
An asymmetric route to dihydroquinazolinones via the addition of ortho metalated substrates to tert-butanesulfinyl imines is reported. The scope of the nucleophile and electrophile components and the absolute stereochemical outcome are presented. 相似文献
3.
2-(4-Chlorophenyl)-2-methyl-1,3-dioxolane 2a was lithiated ortho to the ketal group by treatment with butyllithium in THF at 0°C. Related 2-aryl-2-methyl-1,3-dioxolanes possessing a chlorine substituent at the meta position of the aryl group 2b,c were lithiated with butyllithium in THF at −78°C at the position between the two directing groups. The lithio species thus generated were treated with various electrophiles to give ortho-functionalized acetophenone derivatives. 相似文献
4.
Chemoselective synthesis of thioaurones or 3-hydroxy benzo[b]thiophen-2-aryl ketones, 1-hydroxy naphtho[2,1-b]thiophen-2-aryl ketones and chalcones from N,N-diethyl-ortho-methyl sulfanyl aryl amides were described. (Benzo[b]thiophen-2-yl) alkylates and (naphtho[2,1-b]thiophen-2-yl) alkylates undergo a novel anionic ortho-Fries rearrangement leading to (3-hydroxy benzo[b]thiophen-2-yl) and (1-hydroxy naphtho[2,1-b]thiophen-2-yl) alkyl ketones. The hydroxy ketones were used as intermediates in the synthesis of wide range of benzothienopyranones and thiafluorenones. 相似文献
5.
Kazuyuki Sato 《Journal of fluorine chemistry》2003,121(1):105-107
Reaction of ethyl bromodifluoroacetate with a variety of Michael acceptors was tremendously improved by the addition of TMEDA. Using this additive, 1,4-adducts were formed exclusively, and any 1,2-adducts or radical adducts were not obtained. THF or other low boiling solvents can be used as a solvent. This simplifies the work-up of the reaction effectively. 相似文献
6.
7.
This paper describes the commercially-viable synthesis and isolation of 2-ethoxy-3-pyridylboronic acid on a ca. 70 g scale via a directed ortho-metalation reaction on readily-available 2-ethoxypyridine. A range of efficient cross-coupling reactions of 2-ethoxy-3-pyridylboronic acid with selected aryl/heteroaryl halides under palladium-catalysed Suzuki-Miyaura conditions yield novel 2-ethoxy-3-aryl/heteroaryl-pyridines in high yield (heteroaryl=pyridyl, pyrimidyl, pyrazyl). The X-ray crystal structure of 2-ethoxy-3-pyridylboronic acid reveals that the boronic acid group takes part in an intramolecular O-H?O bond with the adjacent ethoxy substituent, and an intermolecular O-H?N bond. 相似文献
8.
9.
A highly convergent and efficient synthesis of (−)-microcarpalide, a 10-membered lactone displaying remarkable microfilament disrupting activity is described. Ring-closing metathesis and Sharpless asymmetric dihydroxylations are the key steps. Our strategy highlights the application of novel hydroxy lactone precursors for the stereoselective synthesis of (−)-microcarpalide. 相似文献
10.
Vyacheslav Ya. Sosnovskikh Alexander V. SafryginViktor A. Anufriev Oleg S. EltsovViktor O. Iaroshenko 《Tetrahedron letters》2011,52(47):6271-6274
While 2-(trifluoromethyl)chromones react with cyanoacetamides in the presence of sodium ethoxide to produce 6-(2-hydroxyaryl)-4-(trifluoromethyl)-2-oxo-1,2-dihydropyridine-3-carbonitriles, their reactions with ethyl cyanoacetate and diethyl malonate under the same conditions took an entirely different course and gave novel functionalized derivatives of 6H-benzo[c]chromen-6-one. 相似文献
11.
The zwitterionic intermediates (2a) in the oxidation of ortho-alkylphenols (1) and bis(sulfonium ylide) 3 form reasonably stable 2:1-complexes (4), in which the ortho-quinone methide (oQM) moieties are not present in quinoid form with the exocyclic in-plane methylene group, but as zwitterionic, aromatic conformer having an out-of-plane exocyclic methylene group. The complex 7 derived from the α-tocopherol model compound PMC (5) was comprehensively characterized. As exemplarily demonstrated, the adducts can be advantageously employed in organic synthesis as ‘stabilized oQMs’. 相似文献
12.
Dewen Dong 《Tetrahedron letters》2005,46(43):7331-7335
A novel and facile synthesis of substituted 2,3-dihydro-1,4-dithiins and 6,7-dihydro-5H-1,4-dithiepins based on the reactions of α-bromo/hydroxy ketones with α-oxo ketene cyclic dithioacetals has been developed. A general mechanism for the reactions is proposed. 相似文献
13.
The total synthesis of the azepinoindole alkaloid, (±)-hyrtiazepine, was achieved. Construction of the azepinoindole core structure was carried out by C-4 selective α-hydroxyalkylation of 5-hydroxyindole, introduction of serine at C-3 of the indole moiety, and intramolecular imination. 相似文献
14.
Lewis acid catalyst-tuned reactions of N′-(2-alkynylbenzylidene)hydrazides with diethyl phosphite are described. Isoquinolin-1-ylphosphonate is generated when copper triflate is utilized as catalyst, while 2-amino-1,2-dihydroisoquinolin-1-ylphosphonate is obtained in the presence of palladium acetate. 相似文献
15.
A new family of the end-capped 5-(N,N-dimethylamino)naphthylethynyl chains were synthesized, as terminal acetylenes or poly(yne) structures, by heterocoupling between 5-iodo-N,N-dimethylnaphthalen-1-amine and 2-methyl-3-butyn-2-ol or 4-(5-iodo-1-naphthyl)-2-methyl-3-butyn-2-ol, catalyzed by the palladium-copper system. Catalytic homocoupling of the terminal acetylenes, affords to 1,4-dinaphthyl-1,3-butadiyne nanostructures. X-ray diffraction analysis of 1,4-di(α-naphthyl)-1,3-butadiyne shows that the naphthalene rings are in the anti configuration along the acetylene axis. All the conjugated compounds show an important fluorescent emission radiation. 相似文献
16.
Tokutaro Ogata Yoshiko SugiyamaSaki Ito Kazuha NakanoEri Torii Arisa NishiuchiTetsutaro Kimachi 《Tetrahedron》2013
The first total synthesis of (±)-lantalucratins A and B is described. Introduction of an alkyl side chain at the 6-position was proceeded by directed ortho-lithiation and subsequent alkylation reaction to afford 6-alkyl-5,7,8-trimethoxy-1-naphthol as a synthetically important intermediate for (±)-lantalucratins A and B in excellent yield with complete regioselectivity. The 1,2-naphthoquinone fused five-membered cyclic ether framework was constructed directly from 3-hydroxyalkyl-naphthalenes by oxidative intramolecular cyclization reaction with diammonium cerium(IV) nitrate. (±)-Lantalucratins A and B were obtained in 69% and 45% overall yields, respectively. 相似文献
17.
Ethyl 2-chloroacetoacetate and its 4-chloro isomer react with cyanoacetamide in the presence of the mild, nonnucleophilic base, triethylamine under stoichiometric conditions to give high yields of ethyl 4-cyano-2-hydroxy-2-methyl-5-oxopyrrolidine-3-carboxylate and ethyl (4-cyano-2-hydroxy-5-oxopyrrolidin-2-yl)acetate, respectively. These, under acid-catalyzed dehydration conditions, afforded ethyl 4-cyano-5-hydroxy-2-methyl-1H-pyrrole-3-carboxylate and ethyl (2Z)-(4-cyano-5-oxopyrrolidin-2-ylidene)ethanoate, respectively. Similarly, the 4-chloro isomer reacted with ethyl cyanoacetate to give the novel product, diethyl 2-cyano-4-oxohexanedioate. The use of triethylamine enables access to a whole new library of pyrrole derivatives from easily accessible, commercially available starting materials. The reactions described in this Letter enable access to libraries of important pyrrole systems in any of the isotopically enriched forms. 相似文献
18.
Olga V. Vinogradova 《Tetrahedron letters》2009,50(46):6358-6941
Cleavage of ortho-(dodeca-1,3-diynyl)triazenes in HCl or HBr medium and subsequent cyclization of the resulting diazonium salts is investigated. In the absence of a strong electron-withdrawing substituent, the reaction affords 3-alkynyl-4-bromo(chloro)cinnolines as the only product. A methoxycarbonyl group promotes hydrolysis of 4-halocinnolines which results in the formation of by-products: furo[3,2-c]cinnoline and cinnolinone. Substitution of bromine in 3-(alk-1-ynyl)-4-bromocinnolines is achieved with methylamine, Na2S and ethynylbenzene affording pyrrolo[3,2-c]cinnoline, thieno[3,2-c]cinnoline and 3,4-diethynylcinnoline, respectively. 相似文献
19.
Natsuhisa Oka 《Tetrahedron》2006,62(15):3667-3673
A novel phosphonium-type condensing reagent, 1,3-dimethyl-2-(3-nitro-1,2,4-triazol-1-yl)-2-pyrrolidin-1-yl-1,3,2-diazaphospholidinium hexafluorophosphate (MNTP), was designed and synthesized. A 31P NMR study on the condensation reactions of phosphate, alkylphosphonate, boranophosphate, and H-phosphonate derivatives with an alcohol in the presence of MNTP demonstrated the versatility and the enhanced activity of the new condensing reagent, compared to the previously reported phosphonium-type condensing reagents. The mechanism of the condensation reactions mediated by MNTP is discussed on the basis of the 31P NMR studies and theoretical calculations. 相似文献
20.
3-Methoxy-5-chloro-6-methyl-2(H)-1,4-oxazin-2-one 4, 3-methoxy-5-chloro-6-phenyl-2(H)-1,4-oxazin-2-one 5, 3-phenylsulfenyl-5-chloro-6-methyl-2(H)-1,4-oxazin-2-one 6, and 3-phenylsulfenyl-5-chloro-6-phenyl-2(H)-1,4-oxazin-2-one 7, are ambident dienes and undergo Diels-Alder cycloadditions with electron neutral, rich and deficient dienophiles. 相似文献