- 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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- Concise Synthesis of Chromene/Chromane-Type Aryne Precursors and Their Applications
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The gram-scale synthesis of 5,6-, 6,7-, and 7,8-chromene/chromane-type aryne precursors and their applications in regioselective transformation to other functional derivatives is reported. Chromene/chromane-type arynes are generated under mild conditions, which can further undergo [2 + 2], [3 + 2], and [4 + 2] cycloaddition reactions, nucleophilic addition reactions, and σ-insertion reactions to produce structurally novel substituted chromenes and chromanes. The excellent regioselectivity of the reaction is facilitated by the oxygen-containing guiding groups at the ortho-position of the triple bond, which can be removed or switched to other functional groups including alkenyl, aryl, heteroaryl, and arylamino groups.
- Xu, Yuan-Ze,Tian, Jia-Wei,Sha, Feng,Li, Qiong,Wu, Xin-Yan
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Precocenes I and II (1a, 1b) were obtained in a one pot reaction from a monophenol and a butenal. Matrix Equation Presented.
- Tiabi, Mourad,Zamarlik, Henri
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- Synthesis of new (±) pterocarpans by Heck oxyarylation
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Among a wide variety of synthetic routes to pterocarpan prototypes, a mild approach uses a reaction known as Heck oxyarylation. This method involves a reaction between 2H-chromenes and 2-chloromercuriophenols in the presence of Li2PdCl4. 2005 Springer Science+Business Media, Inc.
- Sa E Sant'Anna,Evangelista,Alves,Raslan
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- THE SYNTHESIS OF CYCLOPROPYL ANALOGUES OF PRECOCENE I
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A new, short synthesis of precocene I is described together with the synthesis of two cyclopropyl analogues.One of these compounds showed interesting biological activity against the bean aphid, Aphis fabae.
- Mann, John,Kane, Peter D.
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- Gold(I)-Catalyzed Intramolecular Hydroarylation of Phenol-Derived Propiolates and Certain Related Ethers as a Route to Selectively Functionalized Coumarins and 2 H-Chromenes
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Methods are reported for the efficient assembly of a series of phenol-derived propiolates, including the parent system 56, and their Au(I)-catalyzed cyclization (intramolecular hydroarylation) to give the corresponding coumarins (e.g., 1). Simple syntheses of natural products such as ayapin (144) and scoparone (145) have been realized by such means, and the first of these subject to single-crystal X-ray analysis. A related process is described for the conversion of propargyl ethers such as 156 into the isomeric 2H-chromene precocene I (159), a naturally occurring inhibitor of juvenile hormone biosynthesis.
- Cervi, Aymeric,Vo, Yen,Chai, Christina L. L.,Banwell, Martin G.,Lan, Ping,Willis, Anthony C.
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p. 178 - 198
(2020/12/22)
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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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- USE OF COMPOSITIONS OBTAINED BY CALCINING PARTICULAR METAL-ACCUMULATING PLANTS FOR IMPLEMENTING CATALYTICAL REACTIONS
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The use of metal-accumulating plants for implementing chemical reactions especially catalytical reactions.
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Paragraph 0828
(2016/01/25)
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- Enantioselective reduction of 4-chromanone and its derivatives by selected filamentous fungi
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Biotransformation of 4-chromanone and its derivatives in the cultures of three biocatalysts: Didymosphaeria igniaria, Coryneum betulinum and Chaetomium sp. is presented. The biocatalysts were chosen due to their capability of enantiospecific reduction of low-molecular-weight ketones (acetophenone and its derivatives and α- and β-tetralone). The substrates were reduced to the respective S-alcohols with high enantiomeric excesses, according to the Prelog's rule. In the culture of Chaetomium sp. after longer biotransformation time an inversion of configuration of the formed alcohols was also observed. The highest yield of transformation was observed for 6-methyl-4-chromanone. In all the tested cultures, the higher was the molecular weight of a chromanone, the lower conversion percent was observed.
- Janeczko, Tomasz,Dmochowska-Gladysz, Jadwiga,Szumny, Antoni,Kostrzewa-Suslow, Edyta
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p. 278 - 282
(2013/10/22)
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- Ph3PAuNTf2 as a superior catalyst for the selective synthesis of 2H-chromenes: Application to the concise synthesis of benzopyran natural products
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Ph3PAuNTf2 (≈1 mol-%) catalyzes the selective cycloisomerization of substituted aryl propargyl ethers into 2H-chromenes in excellent yields. Benzofuran byproducts are formed only in the case of electron-deficient arenes, in up to 7% relative yield. The Ph 3PAuNTf2-catalyzed cyclization of aryl propargyl ethers was applied as a key step to the concise synthesis of the naturally occurring benzopyrans seselin, xanthyletin, precocenes I and II, 8-(3′,3′- dimethylallyl)wenteria chromene, and 2,2-dimethyl-8-prenylchromene-6-propenoic acid. Ph3PAuNTf2 is a general, highly efficient, and product-selective catalyst for the clean synthesis of 2H-chromenes from the cycloisomerization of aryl propargyl ethers.The Ph3PAuNTf 2-catalyzed cyclization was applied as a key step in the synthesis of several benzopyran-bearing naturally occurring substances. Copyright
- Lykakis, Ioannis N.,Efe, Christina,Gryparis, Charis,Stratakis, Manolis
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experimental part
p. 2334 - 2338
(2011/06/20)
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- Direct, regioselective synthesis of 2,2-dimethyl-2H-chromenes. Total syntheses of octandrenolone and precocenes I and II
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Herein is reported an efficient method for the synthesis of 2,2-dimethyl-2H-chromenes in a single step from the corresponding phenol and 3-methyl-2-butenal via microwave irradiation in CDCl3. This protocol features a mild reaction environment (neutral, no added catalyst) which yields regioselective formation of the chromene and displays tolerance toward acid- and base-sensitive protecting groups.
- Adler, Marc J.,Baldwin, Steven W.
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supporting information; experimental part
p. 5075 - 5079
(2009/12/01)
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- Facile synthesis of 2,2-Dimethylchromans by Mo(CO)6 Catalyzed reaction of aryl prenyl ethers
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2,2-Dimethylchromans 3a-g are synthesized in good yields by a one-pot reaction of the aryl prenyl ethers 1a-g with a catalytic amount of Mo(CO)6 in refluxing toluene.
- Bernard, Angela M.,Cocco, Maria T.,Onnis, Valentina,Piras, Pier P.
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p. 256 - 258
(2007/10/03)
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- Cyclization of o-(3-hydroxy-3-methylbutynyl)-phenols with boron tribromide to 4-bromo-2,2-dimethylchromenes and their electroreduction to 2,2-dimethylchromenes
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Cyclization of o-(3-hydroxy-3-methylbutynyl)phenols (2) with boron tribromide gave easily 4-bromo-2,2-dimethylchromenes (3). Electrolytic reduction of 3 at a Hg-pool electrode afforded the corresponding 2,2-dimethylchromenes (6) in high yields.
- Tsukayama, Masao
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p. 1131 - 1142
(2007/10/03)
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- Amination of o-Alkenylphenols with Alkylamines via Photoinduced Proton Transfer
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Irradiation of o-alkenylphenols with alkylamines resulted in Markovnikov-type amination to give o-(1-alkylaminoalkyl)phenols in relatively good yields. The photoamination was initiated by a proton transfer from the ammonium ion to the alkenyl group of o-alkenylphenolate anion in the excited state in the ion pair formed between the phenols and the amines. The resulting zwitter ion allowed the nucleophilic addition of the amine at the benzylic cation center.
- Yasuda, Masahide,Sone, Tatsuya,Tanabe, Kimiko,Shima, Kensuke
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p. 453 - 456
(2007/10/02)
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- One-pot synthesis of precocene I and II and a formal synthesis of robustadial A and B via 2-phenyl-4H-1,3,2-benzodioxaborin
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The reaction of a phenol, an α,β-unsaturated aldehyde, and phenylboronic acid yields a 2-phenyl-4H-1,3,2-benzodioxaborin. Upon heating, this compound decomposes to an orthoquinone-methide intermediate, which undergoes an electrocyclization reaction to a chromene ring system. This method has been applied to the synthesis of precocenes I and II and the robustadial A and B. The reaction of a phenol, an α,β-unsaturated aldehyde, and phenylboronic acid yields a 2-phenyl-4H-1,3,2-benzodioxaborin. Upon heating, this compound decomposes to an orthoquinone-methide intermediate, which undergoes an electrocyclization reaction to a chromene ring system. This method has been applied to the synthesis of precocenes I and II and the robustadial A and B.
- Bissada,Lau,Bernstein,Dufresne
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p. 1866 - 1869
(2007/10/02)
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- Synthesis of 2,2-Dimethyl-2H-chromenes via a Palladium(II) Catalysed Reaction
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The antijuvenile hormones Precocene-1, Precocene-II and other bioactive 2,2-dimethyl-2H-chromenes have been synthesised by intramolecular oxidative cyclisation of 2-isoprenyl phenols catalysed by a palladium(II) salt.
- Iyer, Meera,Trivedi, G. K.
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p. 1347 - 1351
(2007/10/02)
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- Chromene derivatives and pesticidal composition comprising the same
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The invention relates to a process for the preparation of chromenes of the general Formula V STR1 (wherein R1 and R2 are hydrogen, optionally halogeno substituted C1-6 alkyl or aryl; R3 and R7 stand for hydrogen, halogen or C1-6 alkyl; R4 represents C1-8 alkyl, aryl, aralkyl or a group containing a carbonyl group; R5 and R6 stand for C1-10 alkyl, aryl, amino, hydroxyalkyl, alkoxyalkenyl, alkylmercaptoalkyl, acyl, carboxy or an ester group or a halogen atom; n is 0 or 1) which comprises (a) for the preparation of compounds, in which R5 and R6 stand for different groups, reacting a compound of the general Formula I STR2 with an approximately equimolar, preferably 0.8-1.5 molar amount of a reactant of the general Formula R5 --X-related to the amount of the compound of the general Formula I (wherein R5 has the same meaning as stated above X is halogen) and reacting the O-monosubstituted compound of the general Formula III STR3 (wherein R1 -R6 and n are as stated above) obtained with a 1.1-1.5 molar amount of a compound of the general Formula III (wherein R6 and X are as stated above); or (b) for the preparation of compounds, in which R5 and R6 stand for the same group, reacting a chromanone of the general Formula I (wherein R1 -R4 and m have the meaning as stated above) with a 2-3 molar amount of a compound of the general Formula R5 --X-related to the amount of the compound of the general Formula I (wherein R5 and X are as stated above), preferably in the presence of a base, a catalyst and a solvent, and thereafter reducing the O-substituted chromanone derivative of the general Formula III thus obtained (wherein R1 -R6 and n are as stated above) and dehydrating the chromanol derivative of the general Formula IV STR4 thus obtained (wherein R1 -R6 and n are as stated above) in acidic-aqueous medium. The compounds of the general Formula V are partly new and useful for the preparation of pesticides.
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- STUDIES ON THE SYNTHESIS OF PRECOCENES. THE PHOTO-FRIES REARRANGEMENT OF ESTERS OF α,β-UNSATURATED CARBOXYLIC ACIDS AND META-OXYGENATED PHENOLS
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The photo-Fries rearrangement of a series of aryl esters of α,β-unsaturated carboxylic acids 1a,b and 2 has been investigated, in order to explore the possibilities of this reaction as a key step in the synthesis of precocenes and related compounds.In all cases, the photolysis in hexane does not lead to any observable transformation, but in the presence of potassium carbonate takes place a migration of the acyl group to the two ortho-positions.Additionally, trans-cis photoisomerization occurs with the trans-butenoate 1b.The resulting o-hydroxyketones 4a, 4b, 4c, 5a, 5b, 5c, and 8 are easily and efficiently cyclized to the corresponding 4-chromanones 6a, 6b, 7a, 7b, and 9.A second photo-rearrangement is observed in the case of 9, although the yield is low, due to deactivation by the carbonyl group.Cyclization of 10 gives rise to the tricyclic dichromanone 11.Compounds 6a and 11 are reduced and subsequently dehydrated by known procedures to afford the active chromenes 3 and 12.
- Miranda, Miguel A.,Primo, Jaime,Tormos, Rosa
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p. 673 - 682
(2007/10/02)
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- SYNTHESIS OF ANALOGUES OF NATURAL PRECOCENE I CONTAINING VARIOUS 7-O-SUBSTITUENTS
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Syntheses of analogues of the benzopyran precocene I (I) with various 7-O-substituents are described.The compounds were characterized by IR, MS, (1)H and (13)C-NMR.
- Timar, Tibor,Hosztafi, Sandor,Jaszberenyi, J. Csaba,Koever, Katalin E.,Batta, Gyula
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p. 303 - 312
(2007/10/02)
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- SYNTHESIS OF 2,2-DIMETHYL-2H-CHROMENES
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The antijuvenile hormones precocenes I and II (1,2), and related 2,2-dimethyl-2H-chromenes (12,13) were synthesized by oxidative cyclization of o-isoprenylphenols with m-chloroperbenzoic acid, followed by dehydration of the corresponding 3-chromanols with methyltriphenoxyphosphonium iodide.
- Cortes, Manuel J.,Haddad, Gabriel R.,Valderrama, Jaime A.
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p. 1951 - 1954
(2007/10/02)
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- Studies of Chromens. Part 3. Routes to 2,2-Dimethylchroman-3-ones and 4-Ethyoxycarbonyl-2,2-dimethylchromens. Synthesis of a Stable Chromenopyrazolinone
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2,2-Dimethyl-3,4-epoxychroman (6a) was converted into 2,2-dimethylchroman-3-one which readily underwent ethoxycarbonylation to 4-ethoxycarbonyl-2,2-dimethylchroman-3-one (5c).The derived 4-ethoxycarbonyl-2,2-dimethylchromen (1b) reacted with hydrazine to give the pyrazolidinone (4a), oxidation of which gave the stable pyrazolinone (11).Lead tetra-acetate acetoxylation of 7-methoxy-2,2-dimethylchroman-4-one, followed by metal hydride reduction, afforded the 3,4-diols as a mixture of isomers.The relative proportions of cis and trans isomers could be varied from 1:1 to 5:1, respectively, by the choice of reducing conditions.Acid-catalysed dehydration of the diol mixture gave 7-methoxy-2,2-dimethylchroman-3-one (5b).This was unstable and could not be ethoxycarbonylated, but 4-ethoxycarbonyl-7-methoxy-2,2-dimethylchroman-3-one (5d)/(1j) was obtained by a standard synthesis.
- Anastasis, Panayiotis,Brown, Philip E.
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p. 1431 - 1437
(2007/10/02)
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- A New Preparative Method of 2,2-Dimethyl-2H-chromenes
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2,2-Dimethyl-2H-chromene was prepared from salicylaldehyde and ethyl 3-methyl-2-butenoate (or ethyl α-bromoisobutyrate) in one step.This new method of preparing 2,2-dimethyl-2H-chromene was studied and applied to some 2,2-dimethyl-2H-chromene derivatives.
- Kawase, Yoshiyuki,Yamaguchi, Seiji,Horita, Hisanori,Takeno, Junko,Kameyama, Hideaki
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p. 1153 - 1155
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF 2,2-DIMETHYLCHROMENES FROM 2,2-DIMETHYLCHROMANONES
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2,2-Dimethylchromanones were very easily reduced to the corresponding alcohols by sodium borohydride-palladium chloride, and the alcohols were converted into the corresponding 2,2-dimethylchromenes by dehydration with potassium hydrogensulfate in high yields based on 2,2-dimethylchromanones
- Tsukayama, Masao,Sakamoto, Tsukasa,Horie, Tokunaru,Masamura, Mitsuo,Nakayama, Mitsuru
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p. 955 - 958
(2007/10/02)
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- A New Synthesis of 2,2-Dialkylchromenes: Application to Synthesis of Anti-juvenile Hormones Precocenes I & II
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Enolates of 2-hydroxyacetophenones react with ketones to give cross-condensation products which undergo facile cyclodehydration to 2,2-dialkylchromanones in excellent yield.Reduction of the chromanones with LAH gives chroman-4-ols which on dehydration using p-toluenesulphonic acid give 2,2-dialkylchromenes.The above synthetic scheme has been successfully utilised for the synthesis of anti-juvenile hormones, precocene-I (7-methoxy-2,2-dimethylchromene, Ia) and precocene-II (6,7-dimethoxy-2,2-dimethylchromene, Ib).
- Banerji, A.,Goomer, N. C.
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p. 144 - 146
(2007/10/02)
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