نتایج جستجو برای: Xanthenes

تعداد نتایج: 281  

Journal: :Applied optics 1995
A Fischer C Cremer E H Stelzer

Fluorescence emission after two-photon absorption of coumarins and xanthenes in an alcoholic solution was measured in the tuning range of a femtosecond-pulsed titanium-sapphire laser (750-840 nm). Xanthenes, which have a low one-photon absorption in the near UV, show a higher fluorescence signal after two-photon absorption than the UV-excitable coumarins. When fluxes of 10(28) photons/(cm(2) s)...

Journal: :Organic & biomolecular chemistry 2011
Esther Böss Tim Hillringhaus Jacqueline Nitsch Martin Klussmann

A direct synthesis of substituted xanthenes from salicylaldehydes and cyclohexenones or tetralones has been developed. The reaction is catalysed by Lewis acids like scandium triflate and furnishes substituted xanthenes in good to excellent yields using either microwave or thermal heating. Microwave heating results in significantly shortened reaction times of 30 min and generally higher yields.

Journal: :Organic & biomolecular chemistry 2014
Michaela Kotaskova Okan Osman Oglou Mark Helm

Addition of a single functional handle to the tricyclic moiety of fluorescein results in asymmetric xanthene dyes. Our synthesis of a new class of asymmetric xanthenes proceeds via an unusual SNAr with sulfur nucleophiles on electron rich aromatic xanthenes scaffolds in the absence of a metal catalyst. The resulting 3'-thioethers exhibit high photostability and are conveniently converted into r...

Journal: :Organic & biomolecular chemistry 2010
Ngoc Duc Tran Martin Albicker Lorenz Schneider Nicolai Cramer

A combination of an enantioselective conjugate addition/trapping sequence and a ruthenium(iii)-catalyzed domino cyclization provides a concise access to benzo[d]xanthenes found in several anti-influenza active sesquiterpene natural products.

2012
Ayesha Jacobs Francoise M. Amombo Noa Jana H. Taljaard

In the title compound, C(21)H(18)O(3), the xanthene system and the meth-oxy-phenyl ring are practically orthogonal with a dihedral angle between their mean planes of 89.27 (3)°. The meth-oxy group attached to the phenyl ring makes a C-O-C-C torsion angle of 11.56 (18)°. In the crystal, mol-ecules are linked by C-H⋯O inter-actions into chains along [010]. Weak C-H⋯π inter-actions also occur.

Journal: :Molecules 2012
Kalla Reddi Mohan Naidu Balam Satheesh Krishna Mungara Anil Kumar Palanisamy Arulselvan Shaik Ibrahim Khalivulla Ola Lasekan

Polyethyleneglycol bound sulfonic acid (PEG-OSO₃H), a chlorosulphonic acid-modified polyethylene glycol was successfully used as an efficient and eco-friendly polymeric catalyst in the synthesis of 14-aryl/heteroaryl-14H-dibenzo[a,j]xanthenes obtained from the reaction of 2-naphthol and carbonyl compounds under solvent-free conditions with short reaction times and excellent yields. The biologic...

2014
Zeliha Atioğlu Mehmet Akkurt Aliasghar Jarrahpour Roghayeh Heiran Namık Özdemir

In the title compound, C22H21N3O5, the β-lactam (azetidin-2-one) ring is nearly planar [maximum deviation = 0.010 (1) Å] and makes dihedral angles of 69.22 (5), 55.32 (5) and 89.42 (4)° with the least-squares planes formed by the four C atoms of the morpholine ring, which adopts a chair conformation, the benzene ring and the xanthene ring system, respectively. In the crystal, C-H⋯O hydrogen-bon...

2014
Ísmail Çelik Mehmet Akkurt Aliasghar Jarrahpour Roghayeh Heiran Namık Özdemir

The β-lactam (azetidin-2-one) ring of the title compound, C28H27N3O5, is nearly planar [maximum deviation = 0.010 (1) Å] and makes dihedral angles of 75.77 (5), 52.78 (9) and 88.72 (5)°, respectively, with the benzene ring, the least-squares plane formed by the four C atoms of the morpholine ring, which adopts a chair conformation, and the xanthene ring system. In the crystal, C-H⋯O hydrogen-bo...

2012
Shaaban K. Mohamed Mehmet Akkurt Antar A. Abdelhamid Phillip E. Fanwick Herman Potgeiter

In the xanthene ring system of the title compound, C(23)H(25)BrO(4), the 4H-pyran ring is almost planar [maximum deviation = 0.040 (3) Å] and the cyclo-hexene ring adopts a sofa conformation. The cyclo-hexene ring attached to the xanthene system is puckered [Q(T) = 0.427 (3) Å, θ = 55.0 (4) ° and ϕ = 164.4 (6) °]. In the crystal, mol-ecules are linked to each other by O-H⋯O and C-H⋯O hydrogen b...

2009
B. Palakshi Reddy V. Vijayakumar T. Narasimhamurthy J. Suresh P. L. Nilantha Lakshman

In the title compound, C(23)H(26)O(3), the three six-membered rings of the xanthene system are non-planar, having total puckering amplitudes, Q(T), of 0.443 (2), 0.202 (2) and 0.449 (2) Å. The central ring adopts a boat conformation and the outer rings adopt sofa conformations. The crystal structure is stabilized by van der Waals inter-actions.

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