- One-pot synthesis of analogues of precocenes and isoprenyl-chromenes
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A convenient one-pot synthesis of chromenes is described. It results from simultaneous addition and cyclization of differently parasubstituted monophenols and aldehydes of isoprenic type (5 or 10 carbons), heated for several hours in refluxing pyridine (or 4-methylpyridine).
- Lamcharfi,Menguy,Zamarlik
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- Microwave assisted synthesis and anti microbial activity of 2,2-dimethyl chromenes
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2,2-Dimethyl chromenes (1b-9b) were prepared from corresponding propargyl ethers (1a-9a) under microwave conditions in high yields and anti microbial activity of compounds (6b & 7b) is reported.
- Suresh Babu,China Raju,Praveen,Hara Kishore,Suryanarayana Murty,Madhusudana Rao
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- ReCl(CO)5-catalyzed cyclocondensation of phenols with 2-methyl-3-butyn-2-ol to afford 2,2-dimethyl-2H-chromenes
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A direct one-pot route for the synthesis of 2,2-dimethyl-2H-chromenes by Re(CO)5Cl-catalyzed cyclocondensation of phenols with 2-methyl-3-butyn-2-ol has been developed. The easy availability of starting materials, mild reaction conditions, high
- Zeng, Hanxiang,Ju, Jia,Hua, Ruimao
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- An experimental attempt to identify a moving molecular moiety in a solvent matrix
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It was experimentally demonstrated that microscopic friction between a reactant molecule and the surrounding solvent during a unimolecular structural change increased with increasing bulkiness of substituents and it is suggested that this dependence can be used to identify a moving molecular moiety in the reactant inside of a solvation shell.
- Goto, Yoshitaka,Sugita, Keijiro,Takahashi, Toru,Ohga, Yasushi,Asano, Tsutomu
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- A novel method for the synthesis of substituted benzochromenes by ethylenediamine diacetate-catalyzed cyclizations of naphthalenols to α,β-unsaturated aldehydes. Concise synthesis of the natural products lapachenole, dihydrolapachenole, and mollugin
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A new synthetic route for biologically interesting benzochromenes was developed starting from naphthalenols and α,β-unsaturated aldehydes in the presence of ethylenediamine diacetate. This methodology was applied for the total synthesis of the biologicall
- Yong, Rok Lee,Yun, Mi Kim
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- A new application of high-viscosity kinetics. An attempt to identify a site of solvent reorganizations around a reactant
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Thermal fading of a colored species photochemically generated from so-called chromenes was kinetically studied in highly viscous media. The reaction was retarded by an increase in viscosity at viscosities higher than 102 Pas. We propose to use substituent dependence of this retarding effect as a tool to identify the main site of solvent reorganizations around the reactant molecule in the activation step.
- Sugita, Keijiro,Goto, Yoshitaka,Ono, Mikiko,Yamashita, Kazumi,Hayase, Kayoko,Takahashi, Toru,Ohga, Yasushi,Asano, Tsutomu
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- Pd-Catalyzed Formal [3 + 3] Heteroannulation of Allylic gem-Diacetates: Synthesis of Chromene-Based Natural Products and Exploration of Photochromic Properties
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Palladium-catalyzed allylic alkylation reactions of allylic gem-diacetates are rarely explored. This work unveils an unusual chemical reactivity pattern of allylic gem-diacetates and establishes them as new prototypes to synthesize complex benzo[f]chromene systems. Under the reaction conditions, the diacetates behave as 1,3-dicationic equivalents and undergo a [3 + 3] heteroannulation with 2-naphthols (and meta-substituted phenols) to produce novel polycyclic chromenes possessing spiro-, tri-, and tetrasubstituted carbon centers. The versatility of the method is demonstrated in the synthesis of several chromene-based bioactive natural products. Further, interesting photochromic properties of the new classes of benzo[f]chromenes are also discovered.
- Kumar, Prashant,Kumar, Pravesh,Venkataramani, Sugumar,Ramasastry
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p. 963 - 970
(2022/01/19)
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- Ligand-controlled regiodivergent π-allyl palladium catalysis enables a switch between [3+2] and [3+3] cycloadditions
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Reported herein is the use of ligands to tune the regioselectivity and reactivity of palladium-catalyzed [3+2] and [3+3] cycloadditions. Diverse synthesis with vinylethylene carbonates (VECs) as well as free naphthols has been explored to construct four different valuable polycyclic frameworks in a broad substrate scope.
- Xia, Yu,Bao, Qiao-Fei,Li, Yuke,Wang, Li-Jing,Zhang, Bo-Sheng,Liu, Hong-Chao,Liang, Yong-Min
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supporting information
p. 4675 - 4678
(2019/05/02)
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- Boronic acid/Br?nsted acid co-catalyst systems for the synthesis of 2: H -chromenes from phenols and α,β-unsaturated carbonyls
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Protocols for the synthesis of substituted 2H-chromenes from α,β-unsaturated carbonyls and phenols are described. Optimal combinations of arylboronic acids and Br?nsted acids have been identified, such that both can be employed in catalytic quantities to accelerate these condensations. The method has been used to synthesize a variety of substituted 2H-chromenes, as well as photochromic naphthopyrans. The use of pentafluorophenylboronic acid and diphenylphosphinic acid enabled an expansion of the electrophile scope to include α,β-unsaturated ketones. Hall's 'phase-switching' of boronic acids has been exploited to achieve the separation of the two co-catalysts from unpurified reaction mixtures by a simple liquid-liquid extraction.
- Dimakos, Victoria,Singh, Tishaan,Taylor, Mark S.
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p. 6703 - 6711
(2016/07/21)
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- Synthesis of diverse indene derivatives from 1-diazonaphthalen-2(1 H)-ones via thermal cascade reactions
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A sequential Wolff rearrangement of 1-diazonaphthalen-2(1H)-ones followed by trapping of the ketene intermediate with primary and aromatic amines or alcohols and phenols in the presence of various aldehydes generates 1H-indene-3-carboxamides or 1H-indene-3-carboxylates. This constitutes an unprecedented three-component coupling reaction that allows for the synthesis of functionalized indene derivatives under catalyst-free thermal conditions.
- Somai Magar, Krishna Bahadur,Lee, Yong Rok
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supporting information
p. 4288 - 4291
(2013/09/24)
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- A highly adaptable catalyst/substrate system for the synthesis of substituted chromenes
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The gold(i)-catalyzed endo-cyclization of o-(1-hydroxyallyl)phenols to form chromenes is reported. The title compounds are prepared in high yield from readily available substrates. The system tolerates both electron rich and deficient aryl rings and a high degree of substitution on the allyl moiety.
- Aponick, Aaron,Biannic, Berenger,Jong, Michael R.
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supporting information; experimental part
p. 6849 - 6851
(2010/10/21)
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- Phenylboronic acid-mediated synthesis of 2H-Chromenes
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Condensation of phenols with but-2-enal and 3-methyl-but-2-enal in the presence of phenylboronic acid in acetic acid-toluene solution leads to substituted and condensed 2H-chromenes, constituting a mild and advantageous complement to classical routes for this class of heterocycles.
- Chauder, Brian A.,Lopes, Claudio C.,Lopes, Rosangela S. C.,Da Silva, Alcides J. M.,Snieckus, Victor
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p. 279 - 282
(2007/10/03)
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- Synthesis and Photochromic Behaviour of Naphthopyrans, Pyranoquinolines, Pyranoquinazolines and Pyranoquinoxalines
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New chromenes annulated with different six-membered azaheterocycles were prepared, i.e., the 3H-pyrano[3,2-f]quinolines 9/10 and 14, the 8H-pyrano[2,3-h]isoquinoline 11, the 8H-pyrano[3,2-f]quinazoline 12, the 8H-pyrano[3,2-f]quinoxaline 13, and the 2H-pyrano[2,3-f]isoquinoline 15. The synthesis was achieved using conveniently substituted α,β-unsaturated aldehydes and organotitanium intermediates arising from azaheterocyclic phenols. Their photochromic behaviour (photocolouration yield, UV/VIS spectrum of photomerocyanines, rate constant of thermal bleaching) were studied besides those of corresponding naphthopyrans. The heterocycle effect and the role of substituents in the pyran moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects. Diaryl-substituted azino-fused chromenes, especially isoquinoline derivatives, exhibit increased colourabilities and bathochromically shifted spectra for photomerocyanines which open up new prospects for photochromic applications.
- Pozzo, Jean-Luc,Samat, Andre,Guglielmetti, Robert,Dubest, Roger,Aubard, Jean
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p. 725 - 738
(2007/10/03)
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- REGIOSPECIFIC CATALYTIC ALKENYLATION OF AROMATIC SUBSTRATES WITH COORDINATED DIENES: REACTIONS ON NAPHTHALENE DERIVATIVES. PRELIMINARY RESULTS ON HETEROAROMATIC SUBSTRATES
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α- and β-naphthol undergo regiospecific alkenylation by 1,1-dimethylallene (DMA) at the OH-adjacent β- and α-positions, respectively, when allowed to react with DMA-Pt(II) complex.A catalytic process can be achieved with conversions higher than 90percent.A Pd(II) complex as promotor and isoprene as alkenylating diene can also be used.Similar results were obtained with N-acetyl-β-naphthylamine.Preliminary results indicated that nitrogen-containing heteroaromatic substrates can afford N-, O- or C-isopentenyl derivatives depending on the particular features of the organic ring.
- Renzi, Augusto De,Lombardi, Angelina,Panunzi, Achille,Saporito, Antonio
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p. 657 - 660
(2007/10/02)
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- Synthesis of the Phytoalexin (+/-)-Phaseollin: 3-Phenylthiochromans as Masked 2H-Chromenes and o-Prenyl Phenols
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Phenylthiyl radicals are shown to add regiospecifically to 2H-chromenes to afford 3-phenylthiochromans (8), (10), (13), (14), and (15).The sulphide (15), as equivalent to a chromene protected against acid and oxidation, has been used in two syntheses of (+/-)-phaseollin, a major phytoalexin of beans and other legumes, via the sequence (17)->(18)->(19)->(20)->(21)->(+/-)-(1) or (19)->(22)->(23)->(+/-)-(1).Also the 3-phenylthiochromans, on electron transfer from metal naphthalenide or a mercury cathode, open to o-prenylphenols, providing a two step route to biogenetically important phenols from chromenes which is tolerant of free phenol and carbonyl functions and trisubstituted double bonds.
- Mohamed, Salah E. N.,Thomas, Philip,Whiting, Donald A.
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p. 431 - 438
(2007/10/02)
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- CYCLODEHYDROGENATION OF ORTHO-(3,3-DIMETHYLALLYL)PHENOLS WITH TRITYL TETRAFLUOROBORATE
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Trityl tetrafluoroborate has been shown to effect the cyclodehydrogenation of o-(3,3-dimethylallyl)phenols in an efficient manner.
- Barua, P.,Barua, N. C.,Sharma, R.P.
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p. 5801 - 5804
(2007/10/02)
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- Synthesis and antihypertensive activity of substituted trans-4-amino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ols
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A series of novel substituted trans-4-amino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ols was prepared and tested for antihypertensive activity in the conscious deoxycorticosterone acetate (DOCA)/saline treated hypertensive rat. Optimum blood pressure lowering activity requires 6-substitution by a strong electron-withdrawing group, together with a pyrrolidino or piperidino group at the 4 position. Exceptions to this were the 7-nitro-4-pyrrolidine analogue and the 6-nitro-3-chloropropylamine, which retained marked antihypertensive activity. All of these compounds were direct vasodilators and had comparable antihypertensive activity to hydralazine and to the calcium antagonist, nifedipine. The synthetic route to these compounds involves cyclization of propargyl ethers to 2H-1-benzopyrans, followed by conversion via bromohydrins to 3,4-epoxides, which were ring opened with the appropriate amines. Meta-substituted propargyl ethers gave both 5- and 7-substituted benzopyrans on thermal cyclization, the former predominating. A new route to 2,2-dimethyl-7-nitrobenzopyran is described.
- Evans, John M.,Fake, Charles S.,Hamilton, Thomas C.,Poyser, Robert H.,Watts, Eric A.
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p. 1582 - 1589
(2007/10/02)
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- An Elegant Synthesis of Naphthopyrans
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1-Naphthol on condensation with 2-methyl-1,3-butadiene (isoprene) in the presence of orthophosphoric acid affords 3,4-dihydro-2,2-dimethyl-2H-naphthopyran (I), which on dehydrogenation with DDQ or NBS yields 2,2-dimethyl-2H-naphthopyran (II).Similarly the corresponding isomers, viz. 1,2-dihydro-3,3-dimethyl-3H-naphthopyran (III) and 3,3-dimethyl-3H-naphthopyran (IV) have been synthesised starting from 2-naphthol.
- Ahluwalia, V. K.,Hira, P. K.,Jolly, R. S.
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p. 961 - 962
(2007/10/02)
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- A Novel Synthesis of 2,2-Dimethylnaphthopyran, 3,4-Dihydro-2,2-dimethylnaphthopyran and Their Isomers
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1-Naphthol on treatment with 2-chloro-2-methylbut-3-yne followed by cyclisation with N,N-dimethylaniline affords 2,2-dimethylnaphthopyran (II) which on catalytic reduction furnishes 3,4-dihydro-2,2-dimethylnaphthopyran (I).Similarly the corresponding isomers 2,2-dimethylnaphthopyran (IV) and 3,4-dihydro-2,2-dimethylnaphthopyran (III) have been synthesised starting from 2-naphthol.
- Rohatgi, B. K.,Gupta, R. B.,Khanna, R. N.
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p. 505 - 506
(2007/10/02)
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