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Pyran Ring (pyran + ring)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Enantioselective Synthesis of the Originally Proposed Usneoidone Structure: Evidence for a Structural Revision

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2004
Michèle Danet
Abstract The enantioselective synthesis of the initially proposed structure of usneoidone has been completed according to a convergent strategy in which the key steps were an enantioselective Michael addition involving chiral imines to set up the C12 quaternary center, and the final assembly of the chiral pyran moiety with the aromatic subunit through a cyanohydrin anion alkylation step. The obtained product displays spectroscopic data that significantly differ from the reported values. A putative revised structure in which the pyran ring is opened is proposed for usneoidones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

A novel chelatofore functionalized spiropyran of the 2-oxaindane series

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009
Antony O. Bulanov
A novel chelatofore functionalized spiropyran of the 2-oxaindane series, namely 8-formyl-7-hydroxy-3,,3,-dimethylspiro[2H -chromene-2,1,(3,H)-2-benzofuran], C19H16O4, is reported. In the crystalline state, dimers are formed as a result of the ,,, stacking of aromatic groups of the 2H -chromene part of the molecule and C,H...O interactions. The Cspiro,O bond length in the pyran ring is 1.4558,(10),Å, which is longer than or equal to the bond length in thermo- and photochromic 2-oxaindane spiropyrans synthesized previously, except for the 7,8-benzo/6-NO2 derivative, in which this bond length is 1.465,(2),Å. [source]

5-Acetyl-2-amino-6-methyl-4-phenyl-4H -pyran-3-carbonitrile and 2-amino-5-benzoyl-6-methyl-4-phenyl-4H -pyran-3-carbonitrile acetonitrile solvate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2006
Vladimir N. Nesterov
The syntheses, X-ray structural investigations and calculations of the conformational preferences of the carbonyl substituent with respect to the pyran ring have been carried out for the two title compounds, viz. C15H14N2O2, (II), and C20H16N2O2·C2H3N, (III), respectively. In both molecules, the heterocyclic ring adopts a flattened boat conformation. In (II), the carbonyl group and a double bond of the heterocyclic ring are syn, but in (III) they are anti. The carbonyl group forms a short contact with a methyl group H atom in (II). The dihedral angles between the pseudo-axial phenyl substituent and the flat part of the pyran ring are 92.7,(1) and 93.2,(1)° in (II) and (III), respectively. In the crystal structure of (II), intermolecular N,H,N and N,H,O hydrogen bonds link the molecules into a sheet along the (103) plane, while in (III), they link the molecules into ribbons along the a axis. [source]

The fungal metabolite austdiol

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2003
Leonardo Lo Presti
The title compound, (7R,8S)-7,8-dihydroxy-3,7-dimethyl-6-oxo-7,8-dihydro-6H -isochromene-5-carbaldehyde, C12H12O5, is a trans -vicinal diol. Of the two fused rings, which lie approximately in the same plane, the pyran ring is almost perfectly planar, while the cyclohexenone ring adopts a slightly distorted half-chair conformation. The crystal packing is dictated by two strong intermolecular O,H,O interactions, one involving hydroxy and keto groups, the other involving two hydroxy groups. Molecules are linked together through twofold axes, forming zigzag ribbons extended along the a axis. [source]

2-Amino-4-(1-naphthyl)-5-oxo-5,6,7,8-tetrahydro-4H -chromene-3-carbonitrile and 2-amino-7,7-dimethyl-4-(1-naphthyl)-5-oxo-5,6,7,8-tetrahydro-4H -chromene-3-carbonitrile

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2004
Vladimir N. Nesterov
Syntheses and X-ray structural investigations have been carried out for the two title compounds, C20H16N2O2, (IIIa), and C22H20N2O2, (IIIb). In (IIIa), the heterocyclic ring adopts a sofa conformation, while in (IIIb), the ring has a flattened boat conformation. In both molecules, the fused cyclohexenone ring adopts a sofa conformation. The dihedral angles between these two flat fragments are 3.5,(2) and 17.5,(2)° in (IIIa) and (IIIb), respectively. The dihedral angles between the pseudo-axial naphthalene substituents and the planes of the pyran rings are 90.9,(1) and 96.7,(1)°, respectively. In the crystal structure of (IIIa), intermolecular N,H,N and N,H,O hydrogen bonds link the molecules into infinite tapes along the b axis, while molecules of (IIIb) form centrosymmetric dimers via N,H,N hydrogen bonds, with only one H atom of the NH2 donor group taking part in hydrogen bonding. [source]