Showing papers on "Benzopyrans published in 2001"

Hydroxylated/carboxylated naphthopyrans

Abstract: Described are novel photochromic hydroxylated/carboxylated naphthopyran compounds, examples of which are certain 2H-naphtho[1,2-b]pyrans, 3H-naphtho[2,1-b]pyrans and indeno[2,1-f]naphtho[1,2-b]pyrans each having at least one hydroxylated/carboxylated substituent. Specific substituents are also present on the naphtho, indeno and/or pyrano portions of the compounds. These compounds may be represented by the graphic formulae (I), (II) and (III). Also described are various substrates, e.g., paper, glass, polymeric organic materials, etc., that contain or that are coated with such compounds. Optically clear articles such as contact lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., certain other naphthopyrans, indenonaphthopyrans, benzopyrans, oxazine-type compounds, etc., are also described.

Photochemistry of Photochromic Benzopyrans Studied by Time-Resolved Absorption Spectroscopy:

Abstract: Photochromic reactions of 2H-benzopyrans have been extensively studied to design new materials for commercial applications such as optical memories. Photochromism of 2H-benzopyrans proceeds from a ...

Synthesis and Photochromic Behaviour of Novel 2H-1-Benzopyrans (=2H-Chromenes) Derived from Carbazololes

Abstract: The synthesis and photochromic properties of new 2,2-diphenyl-2H-1-benzopyrans, fused to an indole moiety, are described. All compounds exhibit photochromic behaviour in solution at room temperature. The heteroanellation effects are variable and depend on the position and geometry of the fused indole moiety. A general bathochromic shift in the spectra of the open forms is observed. The presence of a N-methyl group prevents the broadening of the absorption spectra and promotes the instability of some photoinduced forms of compounds with the indole moiety fused at the 5,6 positions of the 2H-1-benzopyran skeleton. The enhanced photocolouration efficiency in the near-UV and the kinetics of thermal bleaching indicate that the novel compounds with an indole moiety fused at the 6,7 positions, particularly those with a linked thiophene moiety, are very interesting molecules for applications in the field of variable optical absorption systems.

Novel photochromic indenonaphthopyran compounds

Abstract: Described are novel reversible photochromic indenonaphthopyran compounds, examples of which are 2H-naphtho[1,2-b]pyrans characterized by having a substituted or unsubstituted indeno group fused at the 2,3 positions of the group to the l side of the 2H-naphthopyran. The compounds also have substituents at the 3 position of the pyran ring. Substituents may also be present at the number 5, 6, 7, 8, 9, 10, 11, 12, or 13 carbon atoms of the compounds. These compounds may be represented by the following graphic formulae: (I). Also described are various substrates, e.g., paper, glass, organic polymeric materials, etc., that contain or that are coated with such compounds. Optically clear articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel indenonaphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., indenonaphthopyrans, naphthopyrans, benzopyrans, oxazine-type compounds, etc., are also described.

An Improved Method for Synthesis of 1‐Benzopyrans from Unsaturated Alcohols and Phenols Using a Catalytic Amount of Acids.

Abstract: 1-Benzopyrans, such as chromans and chromenes, were prepared in good to excellent yields by using a catalytic amount of p-toluenesulfonic acid through intermolecular cyclization reaction of phenols with unsaturated alcohols in 1,2-dichlroroethane.

Method for resolving chiral (2s) and (2r) chromanes

Abstract: Disclosed are processes for resolving chiral (2S) and (2R) benzopyrans, racemizing benzopyrans, and recycling racemized benzopyrans to increase yield of a desired enantiomer to provide purified or substantially purified bicyclic amino substituted benzopyran derivatives. Such benzopyran derivatives are preferably chromans which can be coupled with benzoyl derivatives via an amide bond to produce potent platelet aggregation inhibitors.

Substituted photochromic 2h-naphtho 1,2-b] pyran compounds

Abstract: Described are novel reversible photochromic naphthopyran compounds, examples of which are compounds having a cycloalkyl ester substituent at the number 5 carbon atom and optionally certain substituents at the number 6 carbon atom of the naphtho portion of the naphthopyran and certain substituents at the 2-position of the pyran ring. Substituents may also be present at the number 7, 8, 9 or 10 carbon atoms of the naphtho portion of the naphthopyran. These compounds may be represented by the graphic formula (I). Also described are various substrates, e.g., paper, glass, organic polymeric materials, etc., that contain or that are coated with such compounds. Optically clear articles such as ophthalmic lenses or other plastic transparencies that incorporate the novel naphthopyran compounds or combinations thereof with complementary photochromic compounds, e.g., certain other naphthopyrans, indenonaphthopyrans, benzopyrans, oxazine-type compounds, etc., are also described.

Benzopyrans from Hypericum polyanthemum

Abstract: From the aerial parts of Hypericum polyanthemum Klotzsch ex Reichardt (Guttiferae), three chromenes, 6-isobutyryl-5,7-dimethoxy-2,2-dimethyl-benzopyran; 7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethyl-benzopyran and 5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethyl-benzopyran were isolated. Their structures were determined by NMR spectroscopic analyses.

Photochemical Synthesis of Cyclopenta[c]-Anellated Benzopyrans and Benzothiopyrans

Abstract: Synthesis 2001, No. 8, 18 06 2001. Article Identifier: 1437-210X,E;2001,0,08,1111,1113,ftx,en;C00401SS.pdf. © Georg Thieme Verlag Stuttgart · New York ISSN 0039-7881 Abstract: On irradiation in the presence of 2,3-dimethylbut-2-ene the newly synthesized 2-oxo-2H-1-benzopyranand 2-oxo-2H-1benzothiopyran-4-carbonitriles are converted selectively to a cyclopenta[c]benzopyran or -thiobenzopyran, respectively. The reaction proceeds via addition of the alkene to the nitrileand olefinic C-atoms of the triplet excited coumarin derivatives.

Sc(OTf)3-Catalyzed Diastereoselective Synthesis of 3,4-Dihydro-4-amino-2H-1-benzopyrans.

Abstract: 2,2-Dimethoxypropane reacts with a variety of o-hydroxybenzaldimines in the presence of a catalytic amount of scandium triflate at ambient temperature to afford a series of new compounds, 3,4-dihydro-4-amino-2-methoxy-2-methyl-2H-1-benzopyrans, in high yields, with good diastereoselectivity. BF3·OEt2 is also found to mediate this transformation under mild reaction conditions.

2‐Imino‐2H‐1‐benzopyrans as Versatile Synthons in Heterocyclic Synthesis: Studies on Novel Rearrangements of 3‐Substituted 2‐Imino‐2H‐1‐benzopyrans under Action of N‐Nucleophiles

Abstract: A new chemoselective approach to synthesis of a series of 3-substituted coumarin derivatives and 6substituted benzo[4,5]imidazo[1,2-a]quinolines was developed. It was based on novel rearrangements of different 3-substituted 2-imino-2H-1-benzopyrans 1 (2-imino-2H-1-benzopyran-3-carboxamide and 2-imino-3-(1Hbenzoimidazol-2-yl)-2H-1-benzopyran) under action of N-nucleophiles. By using this methodology, two series of heterocyclic systems were synthesized, namely: i) containing coumarin (2-oxo-2H-1-benzopyran) moiety substituted at C-3 position with different heterocycles such as 4H-1,2,4-triazole (7 and 10), 1,3,4-oxadiazole (8), 1,3,4-thiadiazole (9), 5-oxo-1,4dihydro-benzo[e][1,2,4]triazepine (12), 1,1-dioxo-2H-benzo[e][1,2,4]thiadiazine (13), 4-oxo-3H-quinazoline (17), 4-oxo-5,6,7,8-tetrahydro-3H-benzo[4,5]thieno[2,3-d]pyrimidine (19), 1H-benzoimidazole (20), benzooxazole (21), benzothiazole (22), and ii) comprising benzo[4,5]imidazo[1,2-a]quinoline backbone substituted at C-6 position with 1Hbenzoimidazole (23) and benzooxazole (24) units. Possible mechanisms of the revealed rearrangements were discussed and this approach is considered to be a new and efficient alternative route to a variety of heterocyclic compounds.

Synthesis of E‐ and Z‐Substituted Methylene‐3,4‐dihydro‐2H‐1‐benzopyrans by Regio‐ and Stereocontrolled Palladium‐Catalyzed Intramolecular Cyclization.

Abstract: A stereocontrolled synthetic approach to E - and Z -substituted methylene-3,4-dihydro-2 H -1-benzopyrans 5 is described from acyclic derivatives using as a key step the palladium-catalyzed intramolecular cyclic carbopalladation of iodoalkynes 4 followed by a carbonylation or a hydride ion capture process.