Synthesis of a hyperbranched polythioketal with 100% degree of branching

A 100% hyperbranched polymer was successfully prepared by using 2‐[4‐(4‐mercaptobutoxy)phenoxy]‐9H‐fluoren‐9‐one as an AB₂ monomer in trifluoroacetic acid. The kinetics of the model reaction between 9‐fluorenone and 3‐mercaptopropionic acid was investigated. The reaction obeyed the second‐order kinetics, indicating that the first reaction, that is, the formation of the intermediate from 9‐fluorenone and 3‐mercaptopropionic acid, is considerably slower than the second one, that is, the reaction of the intermediate with 3‐mercaptopropionic acid. On the basis of this finding, a new monomer expected to produce a 100% branched hyperbranched polymer, 2‐[4‐(4‐mercaptobutoxy)phenoxy]‐9H‐fluoren‐9‐one, was designed and prepared. The obtained polymer was characterized by ¹H and ¹³C‐NMR spectroscopy, which confirmed that the polymer was a 100% branched hyperbranched polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2689–2700, 2008     

Synthesis and characterization of novel (9H‐fluoren‐9‐ylamino) carbonylaminomethylphosphonic acid

The new α‐aminophosphonic acids are synthesized, reacting (9H‐fluoren‐9‐yl)urea with formaldehyde and phosphorus trichloride. (9H‐Fluoren‐9‐yl)urea was prepared from spiro(fluoren‐9,4′‐imidazolidine)‐2′,5′‐dione by alkaline hydrolysis with Ba(OH)₂. The structure of the title compounds was proved by means of IR, ¹H, ¹³C, and ³¹P NMR spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:719–722, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20500     

9‐(1‐Acetoxy­ethyl­idene)­fluorene (`diacetyl­fluorene'), a by‐product from the acetyl­ation of 9‐fluorenyl­lithium

Treatment of 9‐fluorenyl­lithium with acetyl chloride produces 9‐acetyl­fluorene, (I), and several by‐products, among which is `di­acetyl­fluorene', now characterized definitively as 9‐(1‐acetoxy­ethyl­idene)­fluorene [IUPAC name: (1‐fluoren‐9‐yl­idene­)ethyl acetate], (II), C₁₇H₁₄O₂, derived from acetyl­ation of initially formed (I). Various parameters disclose substantial structural distortion within (II) emanating from A^(1,3) strain associated with the 9‐(acetoxy­ethyl­idenyl)­fluorene system.     

Ultrafast Relaxation Dynamics of the Excited States of 1‐Amino‐ and 1‐(N,N‐Dimethylamino)‐fluoren‐9‐ones

The dynamics of the excited states of 1‐aminofluoren‐9‐one (1AF) and 1‐(N,N‐dimethylamino)‐fluoren‐9‐one (1DMAF) are investigated by using steady‐state absorption and fluorescence as well as subpicosecond time‐resolved absorption spectroscopic techniques. Following photoexcitation of 1AF, which exists in the intramolecular hydrogen‐bonded form in aprotic solvents, the excited‐state intramolecular proton‐transfer reaction is the only relaxation process observed in the excited singlet (S₁) state. However, in protic solvents, the intramolecular hydrogen bond is disrupted in the excited state and an intermolecular hydrogen bond is formed with the solvent leading to reorganization of the hydrogen‐bond network structure of the solvent. The latter takes place in the timescale of the process of solvation dynamics. In the case of 1DMAF, the main relaxation pathway for the locally excited singlet, S₁(LE), or S₁(ICT) state is the configurational relaxation, via nearly barrierless twisting of the dimethylamino group to form the twisted intramolecular charge‐transfer, S₁(TICT), state. A crossing between the excited‐state and ground‐state potential energy curves is responsible for the fast, radiationless deactivation and nonemissive character of the S₁(TICT) state in polar solvents, both aprotic and protic. However, in viscous but strong hydrogen‐bond‐donating solvents, such as ethylene glycol and glycerol, crossing between the potential energy surfaces for the ground electronic state and the hydrogen‐bonded complex formed between the S₁(TICT) state and the solvent is possibly avoided and the hydrogen‐bonded complex is weakly emissive.     

A Facile and Expeditious Microwave‐Assisted Synthesis of Furo[3,4‐b]indeno[2,1‐f]quinolin‐1‐one Derivatives via Multicomponent Reaction

A series of furo[3,4‐b]indeno[2,1‐f]quinolin‐1‐one derivatives were synthesized by the condensation of an aromatic aldehyde with tetronic acid and 9H‐fluoren‐2‐amine in solvent of glacial acetic acid under microwave irradiation. This procedure offers several advantages including operational simplicity, clean reaction, and increased safety for small‐scale high‐speed synthesis.     

Characterization of Nα-Fmoc-protected ureidopeptides by electrospray ionization tandem mass spectrometry (ESI-MS/MS): differentiation of positional isomers

Four pairs of positional isomers of ureidopeptides, FmocNH‐CH(R₁)‐φ(NH‐CO‐NH)‐CH(R₂)‐OY and FmocNH‐CH(R₂)‐φ(NH‐CO‐NH)‐CH(R₁)‐OY (Fmoc = [(9‐fluorenyl methyl)oxy]carbonyl; R₁ = H, alkyl; R₂ = alkyl, H and Y = CH₃/H), have been characterized and differentiated by both positive and negative ion electrospray ionization (ESI) ion‐trap tandem mass spectrometry (MS/MS). The major fragmentation noticed in MS/MS of all these compounds is due to ? N? CH(R)? N? bond cleavage to form the characteristic N‐ and C‐terminus fragment ions. The protonated ureidopeptide acids derived from glycine at the N‐terminus form protonated (9H‐fluoren‐9‐yl)methyl carbamate ion at m/z 240 which is absent for the corresponding esters. Another interesting fragmentation noticed in ureidopeptides derived from glycine at the N‐terminus is an unusual loss of 61 units from an intermediate fragment ion FmocNH = CH₂⁺ (m/z 252). A mechanism involving an ion‐neutral complex and a direct loss of NH₃ and CO₂ is proposed for this process. Whereas ureidopeptides derived from alanine, leucine and phenylalanine at the N‐terminus eliminate CO₂ followed by corresponding imine to form (9H‐fluoren‐9‐yl)methyl cation (C₁₄H₁₁⁺) from FmocNH = CHR⁺. In addition, characteristic immonium ions are also observed. The deprotonated ureidopeptide acids dissociate differently from the protonated ureidopeptides. The [M ? H]^? ions of ureidopeptide acids undergo a McLafferty‐type rearrangement followed by the loss of CO₂ to form an abundant [M ? H ? Fmoc + H]^? which is absent for protonated ureidopeptides. Thus, the present study provides information on mass spectral characterization of ureidopeptides and distinguishes the positional isomers. Copyright © 2010 John Wiley & Sons, Ltd.     

Modulating the Optoelectronic Properties of Large,Conjugated, High‐Energy Gap,Quaternary Phosphine Oxide Hosts: Impact of the Triplet‐Excited‐State Location

The purposeful modulation of the optoelectronic properties was realised on the basis of a series of the large, conjugated, phosphine oxide hosts 9,9‐bis‐{4′‐[2‐(diphenylphosphinoyl)phenoxy]biphenyl‐4‐yl}‐9H‐fluorene (DDPESPOF), 9,9‐bis‐{3′‐(diphenylphosphinoyl)‐4′‐[2‐(diphenylphosphinoyl)phenoxy]biphenyl‐4‐yl}‐9H‐fluorene (DDPEPOF), 9‐[4′‐(9‐{4′‐[2‐(diphenylphosphoryl)phenoxy]biphenyl‐4‐yl}‐9H‐fluoren‐9‐yl)biphenyl‐4‐yl]‐9H‐carbazole (DPESPOFPhCz) and 9‐[4′‐(9‐{3′‐(diphenylphosphoryl)‐4′‐[2‐(diphenylphosphoryl)phenoxy]biphenyl‐4‐yl}‐9H‐fluoren‐9‐yl)biphenyl‐4‐yl]‐9H‐carbazole (DPEPOFPhCz). The last two are quaternary with fluorenyls as linking bridges, diphenylphosphine oxide (DPPO) moieties as electron acceptors and diphenylethers and carbazolyls as two different kinds of electron donors. Owing to the fine‐organised molecular structures and the mixed indirect and multi‐insulating linkages, all of these hosts achieve the same first triplet energy levels (T₁) of 2.86 eV for exothermic energy transfer to phosphorescent dopants. The first singlet energy levels (S₁) and the carrier injection/transportation ability of the hosts were accurately modulated, so that DPESPOFPhCz and DPEPOFPhCz revealed extremely similar optoelectronic properties. However, the T₁ state of the former is localised on fluorenyl, whereas the carbazolyl mainly contributes to the T₁ state of the latter. A lower driving voltages and much higher efficiencies of the devices based on DPESPOFPhCz indicated that the chromophore‐localised T₁ state can suppress the quenching effects through realising independent contributions from the different functional groups to the optoelectronic properties and the embedding and protecting effect on the T₁ states by peripheral carrier transporting groups.     

Charge‐Transfer‐Assisted Supramolecular 1 D Nanofibers through a Cholesteric Structure‐Directing Agent: Self‐Assembly Design for Supramolecular Optoelectronic Materials

Self‐assembly of pyrene butyric acid (PBA) and 2,4,7‐trinitro‐9H‐fluoren‐9‐one (TNF) directed by a pyridine‐linked cholesterol unit resulted in the formation of a conducting material (1.9472×10^?4 S Cm^?1) due to the formation of 1 D nanofibers. X‐ray diffraction, IR, and atomic force microscopic (AFM) techniques were used to establish the mechanism of the self‐assembly of the multicomponent gels. Results indicate efficient charge transfer in the 1 D nanofibers, assisted by hydrogen bonding.     

Preparation of (S,S)‐Fmoc‐β2hIle‐OH, (S)‐Fmoc‐β2hMet‐OH,and (S)‐Fmoc‐β2hTyr(tBu)‐OH for Solid‐Phase Syntheses of β2‐ and β2/β3‐Peptides

The preparation of three new N‐Fmoc‐protected (Fmoc=[(9H‐fluoren‐9‐yl)methoxy]carbonyl) β²‐homoamino acids with proteinogenic side chains (from Ile, Tyr, and Met) is described, the key step being a diastereoselective amidomethylation of the corresponding Ti‐enolates of 3‐acyl‐4‐isopropyl‐5,5‐diphenyloxazolidin‐2‐ones with CbzNHCH₂OMe/TiCl₄ (Cbz=(benzyloxy)carbonyl) in yields of 60–70% and with diastereoselectivities of >90%. Removal of the chiral auxiliary with LiOH or NaOH gives the N‐Cbz‐protected β‐amino acids, which were subjected to an N‐Cbz/N‐Fmoc (Fmoc=[(9H‐fluoren‐9‐yl)methoxy]carbonyl) protective‐group exchange. The method is suitable for large‐scale preparation of Fmoc‐β²hXaa‐OH for solid‐phase syntheses of β‐peptides. The Fmoc‐amino acids and all compounds leading to them have been fully characterized by melting points, optical rotations, IR, ¹H‐ and ¹³C‐NMR, and mass spectra, as well as by elemental analyses.     

Diaqua­bis[2′‐(4,5‐diaza­fluoren‐9‐yl­idene)picolinohydrazidato‐κ2N,O]zinc(II) tetra­hydrate: a metal–water chain complex containing cyclic water hexa­mers

In the title compound, [Zn(C₁₇H₁₀N₅O)₂(H₂O)₂]·4H₂O, cyclic water hexa­mers forming one‐dimensional metal–water chains are observed. The water clusters are trapped by the co‐operative association of coordination inter­actions and hydrogen bonds. The Zn^II ion resides on a centre of symmetry and is in an octa­hedral coordination environment comprising two O atoms and two N atoms from two 2′‐(4,5‐diaza­fluoren‐9‐yl­idene)picolinohydrazidate ligands and two water mol­ecules.     

The low‐temperature phase transition of 9‐methylfluoren‐9‐ol: comparison of the crystal structures at 100 and 200 K

Crystals of 9‐methyl­fluoren‐9‐ol, C₁₄H₁₂O, undergo a reversible phase transition at 176 (2) K. The structure of the high‐temperature α form at 200 K is compared with that of the low‐temperature β form at 100 K. Both polymorphs crystallize in space group P with Z = 4 and contain discrete hydrogen‐bonded R(8) ring tetramers arranged around crystallographic inversion centres. The most obvious changes observed on cooling the crystals to below 176 K are an abrupt increase of ca 0.5 Å in the shortest lattice translation, and a thermal transition with ΔH = 1 kJ mol^?1.     

Carbo‐Quinoids: Stability and Reversible Redox‐Proaromatic Character towards Carbo‐Benzenes

The carbo‐mer of the para‐quinodimethane core is stable within in a bis(9‐fluorenylidene) derivative. Oxidation of this carbo‐quinoid with MnO₂ in the presence of SnCl₂ and ethanol affords the corresponding p‐bis(9‐ethoxy‐fluoren‐9‐yl)‐carbo‐benzene. The latter can be in turn converted back into the carbo‐quinoid by reduction with SnCl₂, thus evidencing a chemical reversibility of the interconversion between a pro‐aromatic carbo‐quinoid and an aromatic carbo‐benzene, and is reminiscent of the behavior of the benzoquinone/hydroquinone redox couple (in the red–ox opposite sense).     

Effect of the Media on the Quantum Yield of Singlet Oxygen (O2(1Δg)) Production by 9H‐Fluoren‐9‐one: Microheterogeneous Systems

The quantum yield (Φ_Δ) of singlet oxygen (O₂(¹Δ_g) production by 9H‐fluoren‐9‐one (FLU) is very sensitive to the nature of the solvent (0.02 in a highly polar and protic solvent, such as MeOH, to 1.0 in apolar solvents). This high sensitivity has been used for probing the interaction of FLU with micellar media and microemulsions based on anionic (sodium dodecyl sulfate, SDS; bis‐(2‐ethylhexyl)sodium sulfosuccinate, AOT), cationic (cetyltrimethylammonium chloride, CTAC) and nonionic (Triton X‐100, TX) surfactants. Values of Φ_Δ of FLU vary in a wide range (0.05–1.0) in both microheterogeneous media and neat solvent, and provide information on the microenvironment of FLU, i.e., on its localization within organized media. In ionic and nonionic micellar media, as well as in four‐component microemulsions, FLU is, to various extents, exposed to solvation by the polar and protic components of the microheterogeneous systems (water and/or butan‐1‐ol) in the micellar interfacial region (Φ_Δ=0.05–0.30). In contrast, in AOT reverse micelles (consisting of AOT as surfactant, cyclohexane as hydrophobic component, and water), FLU is located in the hydrophobic continuous pseudophase, and is totally separated from the micellar water pools (Φ_Δ≈1.0).     

N‐Benzyl­tetra­hydro­pyrido‐anellated thio­phene derivatives: new anti­cholinesterases

The title compounds, tert‐butyl 6‐benzyl‐2‐(3,3‐diethyl­ureido)‐4,5,6,7‐tetra­hydro­thieno[2,3‐c]pyridine‐3‐carboxyl­ate, C₂₄H₃₃N₃O₃S, (I), 7‐benzyl‐2‐diethyl­amino‐5,6,7,8‐tetra­hydro‐3‐oxa‐9‐thia‐1,7‐diaza­fluoren‐4‐one, C₂₀H₂₃N₃O₂S, (II), and N‐(7‐benzyl‐4‐oxo‐5,6,7,8‐tetra­hydro‐4H‐3,9‐dithia‐1,7‐diaza­fluoren‐2‐yl)benzamide, C₂₃H₁₉N₃O₂S₂, (III), form monoclinic crystal systems. In (I) and (II), the mol­ecules are linked into a three‐dimensional framework by weak inter­molecular C—H⋯O=C hydrogen bonds, whereas in (III) stronger inter­molecular N—H⋯O=C inter­actions are observed. The conformation of (I) is further stabilized by an intra­molecular N—H⋯O=C hydrogen bond, which effects the planarity of the ureido­thio­phene­carboxyl­ate moiety.     

13H‐Dibenzo­[a,i]­fluoren‐13‐one

Molecules of 13H‐dibenzo­[a,i]­fluoren‐13‐one, C₂₁H₁₂O, strad­dle a crystallographic mirror plane and are essentially planar, with a dihedral angle of only 1.9 (1)° between the two naphtha­lene ring systems. Repulsive intramolecular C=O?H interactions therefore do not explain the larger distortions found in isomeric ketones.     

Oligonucleotide Analogues with Integrated Bases and Backbone. Part 28

The protected hydrazide‐linked uracil‐ and adenine‐derived tetranucleoside analogues 17, 19 , and 21 were synthesized in solution by coupling the dimeric hydrazines 6 and 10 with the carboxylic acids 7, 11 , and 16 . These hydrazines and acids were obtained by partially deprotecting the hydrazines 5, 9 , and 15 , and these were prepared by coupling the hydrazines 3 and 14 with the carboxylic acids 4 and 8 . The crystal structure analysis of the fully protected UU dimer 5 showed the formation of an antiparallel cyclic duplex with the uracil units H‐bonded via H? N(3) and O?C(2). Stacking interactions were observed between the uracil units with a buckle twist of 30.9°, and between the uracil unit II and the fluoren‐9‐yl group of Fmoc (=9H‐fluoren‐9‐yl)methoxycarbonyl). The hydrazide H? N(3′) and the C?O group of Fmoc form an intramolecular H‐bond. The uracil‐ and adenine‐derived, water‐soluble hydrazide‐linked self‐complementary octamers 23 – 32 and the non‐self‐complementary uracil derived decamer 33 were obtained by coupling the carboxylic acids 4 and 8 on a solid support. ¹H‐NMR Analysis in CDCl₃, mixtures of CDCl₃ and (D₆)DMSO, and (D₈)THF showed that the partially deprotected dimers 5, 6, 12 , and 13 form weakly associated linear duplexes. The partially deprotected tetramers 17 and 18 do not associate. The hydrazide‐linked octamers 23 – 32 do not stack in aqueous solution, and the non‐self‐complementary decamer 33 does not stack with the complementary strands of DNA 43 and RNA 42 . The Cbz‐protected amide‐linked octamers 51 – 56 derived from uracil, adenine, cytosine, and guanine were obtained as the main products by solid‐phase synthesis from the carboxylic acids 46 – 49 . The fully deprotected amide‐linked octamers proved insoluble, and could neither be purified nor analysed.     

Chloro­bis­(thio­urea‐κS)copper(I) bis(4,5‐di­aza­fluoren‐9‐one) mono­hydrate

The title compound, [CuCl(CH₄N₂S)₂]·2C₁₁H₆N₂O·H₂O, consists of mol­ecules of a Cu^I–thio­urea complex, free 4,5‐di­aza­fluoren‐9‐one (dafone) and crystalline water. The planar complex mol­ecule has trigonal coordination geometry around the Cu^I atom. The dafone and water mol­ecules, which are hydrogen bonded to the Cu^I complex, are approximately coplanar with this complex. The crystal displays a sheet structure and π–π stacking is observed between neighbouring sheets.     

Preparation of 6‐, 7‐, and 8‐substituted derivatives of 2‐Oxa‐1,3,4,10‐tetraazacyclopenta[b]fluoren‐9‐one

The preparation of a variety of derivatives of 2‐oxa‐1,3,4,10‐tetraazacyclopenta[b]fluoren‐9‐one 1 is described. A series of substituted indan‐1‐ones were prepared and oxidized with N‐bromosuccinimide and dimethyl sulfoxide to the corresponding ninhydrin derivatives. Cyclization of the ninhydrins with furazan‐3,4‐diamine yielded the target tetracycles. Appropiate choice of substituents in ninhydrins led to a preference for one regioisomer in the target tetracycles. This permitted the synthesis of a variety of 8‐substituted hetero‐cycles. In those instances where isomer formation was possible, structural assignments were confirmed by X‐ray crystallography.     

A Novel Dual Channel Fluorescent Probe for Ca2+ and Zn2+ Based on a Coumarin Schiff Base

A novel coumarin Schiff base fluorescent probe ethyl 7‐hydroxycoumarin‐3‐carboxylate‐8‐formaldehyde benzoyl hydrazone ( EBH ) has been designed and synthesized which shows solvent dependent dual sensing, viz., recognition of Ca²⁺ in DMF‐H₂O (9∶1, V /V ) solution based on C = N isomerization, photoinduced electron transfer (PET ) inhibition and chelation‐enhanced fluorescence (CHEF ) mechanism as well as detection of Zn²⁺ in H₂O‐CH₃OH (9∶1, V /V ) solution by excited‐state intramolecular proton transfer (ESIPT ) and CHEF processes. The structure of the probe EBH has been confirmed by single‐crystal X‐ray diffraction analysis. Meanwhile, the probe was also used to image intracellular Zn²⁺ ions in MCF ‐7 cells with a good performance.     

Synthesis and transformations of 1-methyl-4-azafluorene

By means of catalytic dehydrocyclization of dimethyl-substituted 2-phenylpyridines in a pyridine ring to 1(2,3)methyl-4-azafluorenes with subsequent oxidation, synthesis of alkaloid onychine — 1-methyl-4-azafluorene — several of its isomers were achieved. Using 1-methyl-4-azafluorene, we obtained a C₉ furfurylidene product, substituted tetrahydroindine[1,2-b]pyridine and NH-indine[1,2-b]-pyridine. We obtained 7-nitro-1-methyl-4azafluorene by nitration of onychine and oxidation of nitro-substituted azafluorene; this indicates an identical orientation of 4-azafluoren(one) and fluoren(one) during nitration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 513–517, April, 1982.