Showing papers on "Benzopyrans published in 2014"
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TL;DR: A metal-free reaction has an excellent functional group tolerance and high chemoselectivity and displays a broad scope with respect to both benzopyran and nucleophile partners, efficiently affording a collection of Benzopyrans bearing diverse skeletons and α-functionalities in one step.
69 citations
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TL;DR: An asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described, and the decarboxylation-assisted release of the catalyst enables the process to proceed efficiently with high enantio- and diastereoselectivity.
Abstract: An asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described. In the synthesis, an unprecedented enantioselective catalytic decarboxylative Diels–Alder reaction is developed using readily available coumarin-3-carboxylic acids and aldehydes as reactants under mild reaction conditions. Notably, the decarboxylation-assisted release of the catalyst enables the process to proceed efficiently with high enantio- and diastereoselectivity. Furthermore, a one-pot procedure for either a LiAlH4- or NaBH4-mediated reduction with subsequent acid-catalyzed intramolecular cyclization of the Diels–Alder adducts was identified for the efficient formation of the chiral bridged tricyclic benzopyrans.
45 citations
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TL;DR: The reaction scope for the transformation was found to be fairly broad, affording good yields of a wide range of flavone- or coumarin-fused benzopyran motifs, which are privileged structures in many biologically active compounds.
Abstract: An efficient and practical method for effecting a tandem C-H alkenylation/C-O cyclization has been achieved via the C-H functionalization of flavone derivatives. The synthetic utility of the one-pot sequence was demonstrated by obtaining convenient access to coumarin-annelated benzopyrans. The reaction scope for the transformation was found to be fairly broad, affording good yields of a wide range of flavone- or coumarin-fused benzopyran motifs, which are privileged structures in many biologically active compounds.
24 citations
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TL;DR: Simple and facile synthetic routes for the preparation of biologically interesting cyclol bearing polycycles were developed using FeCl3-promoted [2 + 2] cycloaddition from readily available benzopyrans possessing a variety of substituents.
Abstract: Simple and facile synthetic routes for the preparation of biologically interesting cyclol bearing polycycles were developed using FeCl3-promoted [2 + 2] cycloaddition from readily available benzopyrans possessing a variety of substituents. As examples of this methodology, one-step syntheses of cannabicyclol, cannabicyclovarin, and ranhuadujuanine A were accomplished in good yield.
23 citations
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TL;DR: The observed diastereoselectivity during O-stannyl ketyl radical cyclization is influenced by aromatic substitution ortho to the aldehyde, whilst acyl radicalcyclization followed by stereoselective reduction of the resulting pyranones provides a complimentary approach to forming the required γ-lactone-fused benzopyran systems.
Abstract: The synthesis of a series of γ-lactone-fused benzopyrans and benzofurans, analogues of the pyranonaphthoquinone antibiotics, is reported. Preparation of the heterocycles was achieved by either O-stannyl ketyl or acyl radical cyclization of benzaldehyde precursors followed by oxidation to give the pyrano- and furanobenzoquinone systems. The observed diastereoselectivity during O-stannyl ketyl radical cyclization is influenced by aromatic substitution ortho to the aldehyde, whilst acyl radical cyclization followed by stereoselective reduction of the resulting pyranones provides a complimentary approach to forming the required γ-lactone-fused benzopyran systems.
18 citations
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TL;DR: 3,4,6-Tri-O-acetyl-D-galactal is selectively converted into 1-O -aryl-2-deoxy derivatives or chiral bridged benzopyrans under Al(OTf)3 catalysis, depending on reaction conditions.
14 citations
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TL;DR: Asymmetric domino oxa-Michael-aldol reactions between trans-cinnamaldehydes and salicylic aldehyde derivatives have been developed as mentioned in this paper, using (2 S,3 aS,7 aS )-diphenylperhydro indolinol silyl ether 4i as the catalyst, most corresponding chiral benzopyrans can be obtained with excellent chemo and enantioselectivities.
Abstract: Asymmetric domino oxa-Michael–aldol reactions between trans -cinnamaldehydes and salicylic aldehyde derivatives have been developed. Using (2 S ,3 aS ,7 aS )-diphenylperhydro indolinol silyl ether 4i as the catalyst, most corresponding chiral benzopyrans can be obtained with excellent chemo- and enantioselectivities.
10 citations
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TL;DR: Poly(4-vinylpyridine) is used as a green, commercially available and recyclable basic catalyst for the multicomponent synthesis of benzopyrans and dihydropyranochromenes by one-pot condensation of aromatic aldehydes, 3-methyl-1-phenyl-2-pyrazolin-5-one, and malononitrile or 4-hydroxycoumarin in ethanol at reflux temperature.
Abstract: Poly(4-vinylpyridine) is used as a green, commercially available and recyclable basic catalyst for the multicomponent synthesis of benzopyrans and dihydropyranochromenes by one-pot condensation of aromatic aldehydes, 3-methyl-1-phenyl-2-pyrazolin-5-one, and malononitrile or 4-hydroxycoumarin in ethanol at reflux temperature. This procedure provides several advantages such as mild reaction conditions, short reaction times, simple work-up and high yields.
6 citations
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TL;DR: O-Stannyl ketyl or acyl radical cyclization of benzaldehyde precursors (I, (IV), and (VIII) followed by oxidation provides access to pyrano- and furanobenzoquinone systems (VII, and (X) as discussed by the authors ).
Abstract: O-Stannyl ketyl or acyl radical cyclization of benzaldehyde precursors (I), (IV), and (VIII) followed by oxidation provides access to pyrano- and furanobenzoquinone systems (VII) and (X).
2 citations
01 Jan 2014
TL;DR: The advances in the use of benzopyrans for the pharmacological properties mainly the cardiovascular properties during the several years are reported in this article, where they can be used for the synthesis of a large variety of heterocyclic compounds, and as raw material for drug synthesis.
Abstract: Benzopyrans (chromene) are synthetically versatile substrates, where they can be used for the synthesis of a large variety of heterocyclic compounds, and as raw material for drug synthesis. The advances in the use of benzopyrans for the pharmacological properties mainly the cardiovascular properties during the several years are reported in this review.
1 citations
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Abstract: An efficient and practical method for effecting a tandem C-H alkenylation/C-O cyclization has been achieved via the C-H functionalization of flavone derivatives. The synthetic utility of the one-pot sequence was demonstrated by obtaining convenient access to coumarin-annelated benzopyrans. The reaction scope for the transformation was found to be fairly broad, affording good yields of a wide range of flavone- or coumarin-fused benzopyran motifs, which are privileged structures in many biologically active compounds.
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TL;DR: A review of novel reaction chemistry and new ring synthetic methods for pyrans is presented in this paper, which covers work published in the calendar year 2011 and includes new ring synthesis methods for Pyranones, coumarins, chromones, xanthenes, xanthones, thiopyrans, dioxins, trioxane, tetraoxanes, dithianes, trithiane, and oxathianes.
Abstract: The review covers work published in the calendar year 2011 Novel reaction chemistry and new ring synthetic methods for pyrans, [1]benzopyrans, dihydro[1]benzopyrans (chromenes, chromans), [2]benzopyrans, dihydro[2]benzopyrans (isochromenes, isochromans), pyranones, coumarins, chromones, xanthenes, xanthones, thiopyrans, dioxins, dioxanes, trioxanes, tetraoxanes, dithianes, trithianes, and oxathianes are reviewed
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TL;DR: In this article, an asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described, and an unprecedented enantioselective catalytic decarboxylative Diels-Alder reaction is developed using readily available coumarin-3-carboxylic acids and aldehydes as reactants under mild reaction conditions.
Abstract: An asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described. In the synthesis, an unprecedented enantioselective catalytic decarboxylative Diels–Alder reaction is developed using readily available coumarin-3-carboxylic acids and aldehydes as reactants under mild reaction conditions. Notably, the decarboxylation-assisted release of the catalyst enables the process to proceed efficiently with high enantio- and diastereoselectivity. Furthermore, a one-pot procedure for either a LiAlH4- or NaBH4-mediated reduction with subsequent acid-catalyzed intramolecular cyclization of the Diels–Alder adducts was identified for the efficient formation of the chiral bridged tricyclic benzopyrans.
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TL;DR: Asymmetric domino oxa-Michael-aldol reactions between trans-cinnamaldehydes and salicylic aldehyde derivatives have been developed as mentioned in this paper, using (2 S,3 aS,7 aS )-diphenylperhydro indolinol silyl ether 4i as the catalyst, most corresponding chiral benzopyrans can be obtained with excellent chemo and enantioselectivities.
Abstract: Asymmetric domino oxa-Michael–aldol reactions between trans -cinnamaldehydes and salicylic aldehyde derivatives have been developed. Using (2 S ,3 aS ,7 aS )-diphenylperhydro indolinol silyl ether 4i as the catalyst, most corresponding chiral benzopyrans can be obtained with excellent chemo- and enantioselectivities.