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1.
The domino Knoevenagel hetero-Diels-Alder reaction of the O-propargylated salicylaldehydes and 4-hydroxycoumarin leads to pyrano[2,3-c]coumarins 3 and pyrano[2,3-c]chromones 4 in high yield in the presence of CuI as a Lewis acid. In all cases, the reaction was shown to exhibit high regioselectivity and form product 3 as main product. 相似文献
2.
Rathna Durga R.S. Manian 《Tetrahedron letters》2007,48(8):1385-1389
Knoevenagal condensation of indole-2-carbaldehyde containing an internal dienophile with coumarins, followed by domino intramolecular hetero Diels-Alder reaction, provides polycyclic heterocycles. Different approaches for stereo- and chemoselective synthesis of indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[5,6-c]coumarin and indolo[2,1-a]pyrrolo[4′,3′:4,5]pyrano[6,5-c]chromone derivatives are described. 相似文献
3.
Mingchuang He Zhaohua Yan Wangyang Wang Fuyuan Zhu Sen Lin 《Tetrahedron letters》2018,59(41):3706-3712
A novel and efficient strategy for the synthesis of furo[3,2-c]coumarins has been developed via copper-catalyzed radical/radical cross-coupling of ketoxime carboxylates with 4-hydroxycoumarins. This redox-neutral reaction allows smooth and selective synthesis of 2-substituted, 3-substituted, 2,3-disubstituted and 2,3-fused polycyclic furo[3,2-c]coumarins. 相似文献
4.
The reaction between 5,7-dihydroxy-4-substituted coumarin, malononitrile, and aromatic aldehydes in the presence of a catalytic amount of K2CO3 as a basic catalyst leads to new pyrano[2,3-h]coumarin derivatives in good to excellent yields. 相似文献
5.
A convenient and efficient procedure for the preparation of 3,4-dihydro-2H-pyran derivatives containing a sugar moiety is described. The reaction sequence is: Knoevenagel condensation of unprotected sugars and CH acids, acetylation of C-glycosides and hetero-Diels–Alder reaction. O-Acetylated 1,3-dimethyl-2,4,6-trioxo-pyrimidin-5-ylidene derivatives were used as new heterodienes in the synthesis of fused uracils—pyrano[2,3-d]pyrimidines with a sugar moiety. Solvent-free hetero-Diels–Alder cycloadditions of O-acetylated pyrimidin-5-ylidene alditols with enol ethers and cyclic enol ether were investigated at room temperature. New, enantiomerically pure cis and trans diastereoisomers of pyrano[2,3-d]pyrimidines and cis–cis, trans–cis diastereoisomers of pyrano[3′,2′:5,6]pyrano[2,3-d]pyrimidines with alditol moiety were obtained. The same pyrimidin-5-ylidene alditols underwent conjugate Michael addition–cyclizations with malononitrile at room temperature to afford optically active diastereoisomers of pyrano[2,3-d]pyrimidine-6-carbonitriles with a sugar moiety. 相似文献
6.
Masoumeh Zakeri Mohamed Mahmoud Nasef Tina Kargaran Arshad Ahmad Ebrahim Abouzari-Lotf Jahanbakhsh Asadi 《Research on Chemical Intermediates》2017,43(2):717-728
Optimization of a green approach to the synthesis of pyrano[2,3-c]pyrazoles based on the one-pot, four-component condensation via a domino Knoevenagel/Michael/cyclization sequence was investigated. This method involved the evaluation of the activity of several ionic liquids (ILs) in various solvents. This one-pot, four-component reaction revealed simplicity, higher yield and lower toxicity advantages over a corresponding three-component method. The effect of reaction parameters including the type and amount of catalyst, type of solvent, reaction temperature and time were studied with respect to yield of pyrano[2,3-c]pyrazoles. Catalyst recyclability and time-saving aspects of the reaction suggest that this method presents real alternatives over conventional reaction protocols. 相似文献
7.
《Tetrahedron letters》2019,60(44):151206
An effective Lewis base catalyst-controlled α-regioselective annulation reaction of γ-substituted allenoates with unsaturated pyrazolones has been developed, affording various spirocyclopentene-pyrazolones and pyrano[2,3-c]pyrazoles. The combination of PPh3 and K2CO3 promoted the [3+2] annulation to access the spirocyclopentene-pyrazolones in moderate to good yields (up to 90%) with excellent diastereoselectivities (dr >19:1), while [4+2] annulations to generate pyrano[2,3-c]pyrazoles were successfully achieved by employing DBU as catalyst (in up to 92% yield). Of importance, the asymmetric synthesis of spirocyclopentene-pyrazolone was realized by using our previously reported chiral ferrocenylphosphine catalyst. 相似文献
8.
Ekambaram Ramesh 《Tetrahedron letters》2008,49(11):1812-1817
A rapid synthesis of pyrrolo[2,3-d]pyrimidine annulated pyrano[5,6-c]coumarin/[6,5-c]chromone derivatives has been accomplished in good yields via an intramolecular domino hetero Diels-Alder reaction using microwave irradiation under solvent-free, solid-supported conditions. 相似文献
9.
V. Yu. Mortikov L. A. Rodinovskaya A. E. Fedorov A. M. Shestopalov P. A. Belyakov 《Russian Chemical Bulletin》2014,63(2):443-456
Formylation of pyrazole and 2,5-dimethylpyrazole gave a number of pyrazole-containing aldehydes, which can be used to obtain chromenes, tetrahydrochromenes, 1,4-dihydropyrano[2,3-c]pyrazoles, pyrano[3,2-c]chromenes, thiochromeno[4,3-b]pyrans, pyrano[3,2-c]-quinolines, and thiazolo[3,2-a]pyridines. 相似文献
10.
Pabitra K. Kalita 《Tetrahedron letters》2006,47(44):7779-7782
Some novel isoxazole and pyrazole fused pyrano[2,3-b]quinolines were synthesized from simple acetanilides via intramolecular 1,3-dipolar cycloaddition reactions involving nitrones, nitrile oxides and nitrile imines as 1,3-dipoles, in a regioselective manner. 相似文献
11.
Wolfgang Holzer Angelika Ebner Karin Schalle Gyselle Batezila Gernot A. Eller 《Journal of fluorine chemistry》2010,131(10):1013-1024
A straightforward, two-step synthesis of fluoro substituted chromeno[2,3-c]pyrazol- and [1]benzothieno[2′,3′:5,6]pyrano[2,3-c]pyrazol-4(1H)-ones, respectively, is presented. Hence, treatment of 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with fluoro substituted 2-fluorobenzoyl chlorides or 3-chloro-6-fluoro-1-benzothiophene-2-carbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane gave the corresponding 4-aroylpyrazol-5-ols, which were cyclized into the fused ring systems. 5-Fluorochromeno[2,3-c]pyrazol-4(1H)-one was obtained upon treatment of the 1-(4-methoxybenzyl) protected congener with trifluoroacetic acid. Treatment of 5-fluorochromeno[2,3-c]pyrazol-4(1H)-ones with methylhydrazine afforded novel tetracyclic ring systems such as 2-methyl-7-phenyl-2,7-dihydropyrazolo[4′,3′:5,6]pyrano[4,3,2-cd]indazole. Detailed NMR spectroscopic investigations (1H, 13C, 15N, 19F) with the obtained compounds were undertaken. 相似文献
12.
Anquan Zheng Tingting Zhou Sasa Wang Wenge Zhang Xiuxiang Lu Huiyu Chen Haibo Tan 《中国化学快报》2022,33(2):885-889
A bioinspired acid-triggered hemiacetalization/dehydration/[3 + 3]-type cycloaddition cascade process was disclosed, diastereoselectively furnishing furo[2,3-b]chromene skeleton under mild conditions. The viability of this approach was demonstrated by syntheses of a series of furo[2,3-b]chromene and pyrano[2,3-b]chromene derivatives. The successful total syntheses of two lignan-phloroglucinol hybrids,hyperaspidinols A and B, exemplified the synthetic utility of our biomimetic methodology. 相似文献
13.
Biswajita Baruah 《Tetrahedron》2009,65(34):7099-431
Some complex pyrano[2,3-b]- and pyrido[2,3-b]quinolines were synthesized from simple acetanilides via intramolecular domino hetero Diels-Alder reactions of 1-oxa-1,3-butadienes using water as solvent. 相似文献
14.
《Tetrahedron letters》2014,55(50):6887-6890
An efficient and convenient synthesis of novel chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidines is described, using the electrogenerated anion of acetonitrile as the base in the presence of tetrabutylammonium fluoride as an effective supporting electrolyte in a one-pot, three-component condensation of barbituric acid, an aromatic aldehyde or isatin, and 4-hydroxycoumarin. The reaction is carried out in an undivided cell containing an iron electrode as the cathode and a Pt electrode as the anode, at a constant current at room temperature. 相似文献
15.
Pegah Farokhian Manouchehr Mamaghani Nosrat Ollah Mahmoodi Khalil Tabatabaeian 《Journal of the Iranian Chemical Society》2018,15(1):11-16
An efficient and practical protocol was developed for the synthesis of novel pyrano[2,3-c]pyrazoles and bis-pyrano[2,3-c]pyrazoles by one-pot four-component reaction of arylaldehyde, ethyl acetoacetate, hydrazine hydrate and dimethyl malonate using SO3H-functionalized ionic liquid [DMBSI]HSO4 as a potential green catalyst under solvent-free condition. The method presented is mild, environmentally friendly, inexpensive and functionality tolerant and produces the desired pyranopyrazoles in short reaction times (17–24 min) and excellent yields (85–95%). In addition, the catalyst can be reused at least ten times without almost any change in its catalytic activity. 相似文献
16.
Priyabrata RoyBinay K. Ghorai 《Tetrahedron letters》2011,52(2):251-253
A new route for the synthesis of furo[2,3-h]quinoline and furo[2,3-h]isoquinoline derivatives have been explored through the coupling of carbene complexes with pyridine-bridged enynes. This reaction process, involving the annulation of both furan and benzene ring on to a pre-existing pyridine ring is highly efficient in the presence of triphenylphosphine as ligand additive. 相似文献
17.
New androsteno[17,16-d]pyrazoles and -pyrazolines with pyrazolo[3,4-d]pyrimidine fragments were synthesized. A reaction of 3β-hydroxypregna-5,16-dien-20-one and its 3-O-acetyl derivative with 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine led to hydrazones at position 20 of the pregnenolone molecule, a possibility of their cyclization was studied. Upon melting, the hydrazones cyclize with the formation of pyrazoline ring annulated with ring D of the steroid at positions 16 and 17. Reflux of the hydrazones in mesitylene with AcOH leads to a mixture of two reaction products: androsteno[17,16-d]pyrazole and a dodecahydro-13H-phenanthro[1′,2′:5,6]pyrano[2,3-d]pyrazole derivative. Apparently, this transformation proceeds through the corresponding epoxide with subsequent rearrangement, which leads to the ring D expansion. 相似文献
18.
Ahmad Shaabani Afshin Sarvary Ali Hossein Rezayan Sajjad Keshipour 《Tetrahedron》2009,65(17):3492-1644
The three-component reaction of the zwitterions generated from dialkyl acetylenedicarboxylate and isocyanides with 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one is described. The reaction afforded the corresponding special type of fully substituted pyrano[2,3-c]pyrazole derivatives in good yields without using any catalyst and activation. 相似文献
19.
France-Aimée Alphonse Céline Cano-Soumillac David Collison John A. Joule 《Tetrahedron》2005,61(46):11010-11019
The synthesis is described of a bis-ene-1,2-dithiolate pro-ligand, designed to model the stereochemical situation in the cofactor of the tungsten enzyme ferredoxin aldehyde oxidoreductase from Pyrococcus furiosus. Each masked ene-1,2-dithiolate unit is mounted on a pyrano[2,3-b]tetrahydroquinoxaline tricycle, comparable to the pyrano[2,3-g]tetrahydropteridines found in all molybdoenzymes and tungsten analogues. Hydrolytic release of the bis-ligand was confirmed by its entrapment as a double (η5-C5H5)Co complex. 相似文献
20.
A microwave-assisted base-free intramolecular cross dehydrogenative coupling (CDC) of 3-aniline substituted coumarins and quinolinones have been developed. A broad range of indolo[2,3-c]coumarins and indolo[2,3-c]quinolinones can be easily afforded in good to high yields (up to 93%) under palladium catalysis. The method is among the most straightforward and convenient ways to access these fused polyheterocycles. 相似文献