Chiral Carboxylic Acid Enabled Achiral Rhodium(III)‐Catalyzed Enantioselective C−H Functionalization

Reported is an achiral Cp^xRh^III/chiral carboxylic acid catalyzed asymmetric C?H alkylation of diarylmethanamines with a diazomalonate, followed by cyclization and decarboxylation to afford 1,4‐dihydroisoquinolin‐3(2H)‐one. Secondary alkylamines as well as nonprotected primary alkylamines underwent the transformation with high enantioselectivities (up to 98.5:1.5 e.r.) by using a newly developed chiral carboxylic acid as the sole source of chirality to achieve enantioselective C?H cleavage by a concerted metalation‐deprotonation mechanism.     

Highly fluorinated low‐molecular‐weight photoresists for optical waveguides

A series of highly fluorinated polymers were synthesized by copolymerization of 2,3,4,5,6‐pentafluorostyrene (PFS) and fluorinated styrene derivate monomer (FSDM). Their chemical structure were confirmed by ¹H NMR, ¹³C NMR, and ¹⁹F NMR spectra. The refractive index and cross‐linking density of the polymers can be tuned and controlled by monitoring the feed ratio of comonomers. A series of negative‐type low‐molecular‐weight fluorinated photoresists (NFPs) were prepared by composing of fluorinated polystyrene derivates (FPSDs), diphenyl iodonium salt as a photoacid generator (PAG) and solvent. The polymer films prepared from NFP by photocuring exhibited excellent chemical resistance and thermal stabilities (T_d ranged from 230.5 to 258.1 °C). A clear negative pattern was obtained through direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel waveguides was measured to be 0.25 dB/cm at 1550 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Stereoselective Ag‐Catalyzed 1,3‐Dipolar Cycloaddition of Activated Trifluoromethyl‐Substituted Azomethine Ylides

A silver‐catalyzed 1,3‐dipolar cycloaddition of fluorinated azomethine ylides and activated olefins is reported. The reaction offers a straightforward and atom‐economical procedure for the preparation of fluorinated pyrrolidines. Broad scope and high levels of diastereoselectivity have been achieved simply by using AgOAc/PPh₃ as the catalyst system. The high efficiency of the cycloaddition relies on the presence of a metal‐coordinating group on the imine moiety, such as an ester or heteroaryl group. The asymmetric version of the cycloaddition has been developed by using Taniaphos as a chiral ligand.     

Palladium‐Catalyzed Suzuki–Miyaura Cross‐Coupling of Secondary α‐(Trifluoromethyl)benzyl Tosylates

A palladium‐catalyzed C(sp³)−C(sp²) Suzuki–Miyaura cross‐coupling of aryl boronic acids and α‐(trifluoromethyl)benzyl tosylates is reported. A readily available, air‐stable palladium catalyst was employed to access a wide range of functionalized 1,1‐diaryl‐2,2,2‐trifluoroethanes. Enantioenriched α‐(trifluoromethyl)benzyl tosylates were found to undergo cross‐coupling to give the corresponding enantioenriched cross‐coupled products with an overall inversion in configuration. The crucial role of the CF₃ group in promoting this transformation is demonstrated by comparison with non‐fluorinated derivatives.     

C−H Direct Arylated 6H‐Indolo[2,3‐b]quinoxaline Derivative as a Thickness‐Dependent Hole‐Injection Layer

A novel perfluoro‐1,4‐phenylenyl 6H ‐indolo[2,3‐b ]quinoxaline derivative ( TFBIQ ) was designed and synthesized by using a C−H direct arylation method. The optoelectrical properties of the obtained TFBIQ were fully characterized by UV/Vis spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and a group of Alq₃‐based green organic light‐emitting diodes (OLEDs). Device A, which used 0.5 nm‐thick TFBIQ as the interfacial modification layer, exhibited the five best advantages of device performance including a minimum turn‐on voltage as low as 3.1 V, a maximum luminescence intensity as high as 26564 cd m⁻², a highest current density value of 348.9 mA cm⁻² at a voltage of 11 V, the smallest efficiency roll‐off, as well as the greatest power efficiency of 1.46 lm W⁻¹ relative to all of the other tested devices with thicker TFBIQ and also 10 nm‐thick MoO₃ as hole‐injection layers (HILs). As a promising candidate for an organic HIL material, the as‐prepared TFBIQ exhibited a strong thickness effect on the performance of corresponding OLEDs. Furthermore, the theoretical calculated vertical ionization potential of the fluorinated TFBIQ suggests better anti‐oxidation stability than that of the non‐fluorinated structure.     

MgII‐Mediated Catalytic Asymmetric Dearomatization (CADA) Reaction of β‐Naphthols with Dialkyl Acetylenedicarboxylates

A Mg^II‐mediated catalytic asymmetric dearomatization (CADA) reaction of β‐naphthols has been developed. The reaction proceeds under ambient temperature and give a series of chiral trisubstituted olefins with good chemoselectivities, Z/E ratios, and excellent enantioselectivities. A fluorinated β‐naphthol was designed to generate chiral organofluorine skeletons through the current CADA reaction. Moreover, an interesting tandem cyclization reaction was observed in the following transformation process through an undiscovered intramolecular hydride transfer pathway.     

Synthesis and characterization of novel fluorinated polyimides derived from 4,4′‐[2,2,2‐trifluoro‐1‐(3‐trifluoromethylphenyl)ethylidene]diphthalic anhydride and aromatic diamines

A novel fluorinated aromatic dianhydride, 4,4′‐[2,2,2‐trifluoro‐1‐(3‐trifluoromethyl‐phenyl)ethylidene]diphthalic anhydride (TFDA) was synthesized by coupling of 3′‐trifluoromethyl‐2,2,2‐trifluoroacetophenone with o‐xylene under the catalysis of trifluoromethanesulfonic acid, followed by oxidation of KMnO₄ and dehydration. A series of fluorinated aromatic polyimides derived from the novel fluorinated aromatic dianhydride TFDA with various aromatic diamines, such as p‐phenylenediamine (p‐PDA), 4,4′‐oxydianiline (ODA), 1,4‐bis(4‐aminophenoxy)benzene (p‐APB), 1,3‐bis(4‐amino‐phenoxy)benzene (m‐APB), 4‐(4‐aminophenoxy)‐3‐trifluoromethylphenylamine (3FODA) and 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene (6FAPB), were prepared by polycondensation procedure. All the fluorinated polyimides were soluble in many polar organic solvents such as NMP, DMAc, DMF, and m‐cresol, as well as some of low boiling point organic solvents such as CHCl₃, THF, and acetone. Homogeneous and stable polyimide solutions with solid content as high as 35–40 wt % could be achieved, which were prepared by strong and flexible polyimide films or coatings. The polymer films have good thermal stability with the glass transition temperature of 232–322 °C, the temperature at 5% weight loss of 500–530 °C in nitrogen, and have outstanding mechanical properties with the tensile strengths of 80.5–133.2 MPa as well as elongations at breakage of 7.1–12.6%. It was also found that the polyimide films derived from TFDA and fluorinated aromatic diamines possess low dielectric constants of 2.75–3.02, a low dissipation factor in the range of 1.27–4.50 × 10^?3, and low moisture absorptions <1.3%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4143–4152, 2004     

Well‐defined poly[(dimethylamimo)ethyl methacrylate]‐b‐poly(fluoroalkyl methacrylate) diblock copolymers: Effects of different fluoroalkyl groups on the solution properties

A series of well‐defined, fluorinated diblock copolymers, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,2‐trifluoroethyl methacrylate) (PDMA‐b‐PTFMA), poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate) (PDMA‐b‐PHFMA), and poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate) (PDMA‐b‐POFMA), have been synthesized successfully via oxyanion‐initiated polymerization. Potassium benzyl alcoholate (BzO^?K⁺) was used to initiate DMA monomer to yield the first block PDMA. If not quenched, the first living chain could be subsequently used to initiate a feed F‐monomer (such as TFMA, HFMA, or OFMA) to produce diblock copolymers containing different poly(fluoroalkyl methacrylate) moieties. The composition and chemical structure of these fluorinated copolymers were confirmed by ¹H NMR, ¹⁹F NMR spectroscopy, and gel permeation chromatography (GPC) techniques. The solution behaviors of these copolymers containing (tri‐, hexa‐, or octa‐ F‐atom)FMA were investigated by the measurements of surface tension, dynamic light scattering (DLS), and UV spectrophotometer. The results indicate that these fluorinated copolymers possess relatively high surface activity, especially at neutral media. Moreover, the DLS and UV measurements showed that these fluorinated diblock copolymers possess distinct pH/temperature‐responsive properties, depending not only on the PDMA segment but also on the fluoroalkyl structure of the FMA units. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2702–2712, 2009     

A Unified Continuous Flow Assembly‐Line Synthesis of Highly Substituted Pyrazoles and Pyrazolines

A rapid and modular continuous flow synthesis of highly functionalized fluorinated pyrazoles and pyrazolines has been developed. Flowing fluorinated amines through sequential reactor coils mediates diazoalkane formation and [3+2] cycloaddition to generate more than 30 azoles in a telescoped fashion. Pyrazole cores are then sequentially modified through additional reactor modules performing N ‐alkylation and arylation, deprotection, and amidation to install broad molecular diversity in short order. Continuous flow synthesis enables the safe handling of diazoalkanes at elevated temperatures, and the use of aryl alkyne dipolarphiles under catalyst‐free conditions. This assembly‐line synthesis provides a flexible approach for the synthesis of agrochemicals and pharmaceuticals, as demonstrated by a four‐step, telescoped synthesis of measles therapeutic, AS‐136A, in a total residence time of 31.7 min (1.76 g h⁻¹).     

ω‐Fluoro Thiafatty Acids: New Mechanistic Probes of Desaturase‐Mediated Reactions

A series of 18‐fluoro thiastearates were prepared and incubated with a yeast Δ9‐desaturating system. The relative efficiency of desaturase‐mediated sulfoxidation was monitored via ¹⁹F‐NMR analysis of the sulfoxide products, and a strong preference for oxo transfer to the S‐atom occupying the 9‐position was confirmed. The oxidation profile obtained in this manner matched that of analogous experiments with non‐fluorinated substrates. These results form the basis of a versatile ¹⁹F‐NMR‐based method for mapping the position of the putative diiron oxidant relative to substrate, and has potential application to the study of membrane‐bound desaturases in vitro.     

Coloring–decoloring behavior of fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid oligomer/acetone composite in methanol

A reddish‐brown fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) oligomer/acetone composite was prepared by heating the white oligomer powder with acetone at 80 °C for 3 h. The color was not observed in the corresponding non‐fluorinated AMPS oligomer/acetone composite, which was prepared under similar conditions. The coloring was probably caused by the formation of acetone polyaldol condensation products in the fluorinated oligomeric gel network cores. The colored R_F‐(AMPS)_n‐R_F/acetone composite powders were stable and did not exhibit any color change after 2 years in natural light at room temperature. The colored composite powders dissolved in methanol to give a reddish‐brown solution at room temperature. However, the retro‐polyaldol condensation decolored the solution after 1 day at room temperature. This is the first example of the retro‐aldol polycondensation of acetone under mild conditions. The decoloration increased by between 38‐ and 70‐fold under UV irradiation, compared with that in dark conditions. The coloring–decoloring behavior was consistent and repeatable; therefore our fluorinated oligomer/acetone composites are promising candidates for new fluorinated coloring materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2555–2564     

Fluoropolyethers end‐capped by polar functional groups. III. Kinetics of the reactions of hydroxy‐terminated fluoropolyethers and model fluorinated alcohols with cyclohexyl isocyanate catalyzed by organotin compounds

The kinetics of the dibutyltin dilaurate (DBTDL)‐catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z‐DOL H‐1000 of various molecular weights (100–1084 g mol^?1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30–60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl‐containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero‐order, first‐order, second‐order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771–3795, 2002     

Perfluorocarbon‐loaded shell crosslinked knedel‐like nanoparticles: Lessons regarding polymer mobility and self‐assembly

Reversible addition‐fragmentation chain transfer polymerization was employed to synthesize a set of copolymers of styrene (PS) and 2,3,4,5,6‐pentafluorostyrene (PPFS), as well as block copolymers with tert‐butyl acrylate (PtBA)‐b‐PS‐co‐PPFS, with control over molecular weight and polydispersity. It was found that the copolymerization of styrene and PFS allowed for the preparation of gradient copolymers with opposite levels of monomer consumption, depending on the feed ratio. Conversion to amphiphilic block copolymers, PAA‐b‐(PS‐co‐PPFS), by removing the protecting groups was followed by fitting with monomethoxy poly(ethylene glycol) chains. Solution‐state assembly and intramicellar crosslinking afforded shell crosslinked knedel‐like (SCK) block copolymer nanoparticles. These fluorinated nanoparticles (ca. 20 nm diameters) were studied as potential magnetic resonance imaging (MRI) contrast agents based on the ¹⁹F‐nuclei; however, it was found that packaging of the hydrophobic fluorinated polymers into the core domain restricted the mobility of the chains and prohibited ¹⁹F NMR spectroscopy when the particles were dispersed in water without an organic cosolvent. Packing of perflouro‐15‐crown‐5‐ether (PFCE) into the polymer micelle was demonstrated with good uptake efficiency; however, it was necessary to swell the core with a good solvent (DMSO) to increase the mobility and observe the ¹⁹F NMR signal of the PFCE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1023–1037, 2009     

Photo‐crosslinked fluorinated thin films from azido‐functionalized random copolymers

Random copolymers of styrene, p‐azidomethylstyrene and 1H,1H,2H,2H‐perfluorodecyl methacrylate were prepared in two steps involving nitroxide‐mediated radical copolymerization and azidation reaction and further characterized by ¹H and ¹⁹F NMR, size exclusion chromatography, differential scanning calorimetry, and thermal gravimetric analysis. Ultrathin films of these azidomethyl‐functionalized fluorinated random copolymers, with thicknesses ranging from 20 to 100 nm, were spin coated onto Si substrates and then crosslinked by ultraviolet irradiation resulting in smooth and insoluble crosslinked fluorinated polymer mats. The surface properties of the supported thin films were investigated by X‐ray photoelectron spectroscopy and water contact angle measurements. These tailored photo‐crosslinked coatings afford a versatile control and homogenization of the wetting properties of different organic and inorganic substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3888–3895, 2010     

Synthesis and Luminescence Property of 4,4＇-Bis（2,2-di（4-fluorophenyl）vinyl）biphenyl for Organic Blue-Light-Emitting Diodes

The novel fluorinated distyrylarylene, 4,4＇-bis（2,2-di（4-fluorophenyl）vinyl）biphenyl （DFPVBi）, was synthesized and fully characterized. The structure was confirmed with IR, 1↑H NMR, 13↑C NMR, 19↑F NMR and MS analyses. Its electronic and photoluminescence properties were investigated by UV-Vis absorption, cyclic voltammetry and fluorescence spectroscopy. The energy levels of the highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO） are --5.77 and --2.75 eV, respectively. The electroluminescence proper- ties of the organic light-emitting diode fabricated by DFPVBi were also studied. The device exhibits a pure blue emission peaked at 454 nm, which indicates a maximum luminance of 5872 cd/m ^2 at 14.2 V and a maximum current efficiency of 2.82 cd/A at 10V, respectively.     

Organosoluble and light‐colored fluorinated polyimides from 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl and aromatic dianhydrides

A novel fluorinated diamine monomer based on 4,4′‐biphenol was synthesized via a straightforward, high‐yielding two‐step procedure. 4,4′‐Biphenol was reacted with 2‐chloro‐5‐nitrobenzotrifluoride in the presence of potassium carbonate to yield the intermediate dinitro compound, which was subsequently reduced to afford the fluorinated diamine, 4,4′‐bis(4‐amino‐3‐trifluoromethylphenoxy)biphenyl. A series of organosoluble fluorinated polyimides were prepared from the diamine with various aromatic dianhydrides via a conventional two‐step thermal imidization method. All polyimides were soluble in strong dipolar solvents such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide. The polyimides showed excellent thermal and thermooxidative stability and good mechanical properties. No significant weight loss was observed below a temperature of 520 °C in nitrogen or in air, and the glass‐transition temperatures ranged from 247 to 313 °C. Low dielectric constants (2.57–3.65 at 10 kHz), low moisture absorption (0.1–0.7 wt %), and low color intensity were also observed. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 524–534, 2002; DOI 10.1002/pola.10113     

Stereospecific radical polymerization of N‐tert‐butoxycarbonylacrylamide in the presence of fluorinated alcohols

Radical polymerization of N‐tert‐butoxycarbonylacrylamide (NBocAAm) in toluene at low temperatures in the presence of the fluorinated alcohols, 2,2,2‐trifluoroethanol, 1,1,1,3,3,3‐hexafluoro‐2‐propanol, and nonafluoro‐tert‐butanol, afforded atactic, heterotactic, and syndiotactic polymers, respectively. NMR analysis revealed that the fluorinated alcohols formed hydrogen bonding‐assisted complexes with NBocAAm, with different structures. The difference in the structures of the complexes was responsible for the differences in the induced stereospecificities. Based on the structures of the complexes between NBocAAm and the fluorinated alcohols, mechanisms for the three kinds of stereospecific radical polymerizations are proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis,Properties, and n‐Type Transistor Characteristics of π‐Conjugated Compounds Having a Carbonyl‐Bridged Thiazole‐Fused Polycyclic System

A series of electron‐deficient π‐conjugated systems with 4,9‐dihydro‐s‐indaceno[2,1‐d:6,5‐d′]dithiazole‐4,9‐dione‐based structures and fluorinated acyl groups as the terminal units have been designed and synthesized for application as organic field‐effect transistor (OFET) materials. The thermal, photophysical, and electrochemical properties and OFET performance of the synthesized compounds were investigated. OFET evaluation revealed that all compounds exhibited typical electron‐transporting characteristics, and electron mobilities up to 0.26 cm² V^?1 s^?1 could be achieved. The air stabilities of OFET operation were dependent on the nature of the compounds and were investigated by X‐ray diffraction and atomic force microscopy. The terminal units had a great influence not only on the molecular properties, but also on the film‐forming properties and OFET performance.     

Carbenoid Pathways in Copper‐Catalyzed Intramolecular Cyclopropanations of Phenyliodonium Ylides

The enantioselectivity of the copper‐catalyzed intramolecular cyclopropanation of allyl diazomalonates and the corresponding phenyliodonium ylides was investigated with a series of chiral, non‐racemic ligands. The reaction of 6b in the presence of the bis[dihydrooxazole] ligand Xa in refluxing 1,2‐dichloroethane proceeded to 8b with an enantiomer excess (ee) of up to 72% under optimized conditions. In contrast, 8b resulting from reaction of ylide 7b with the same ligand, but in CH₂Cl₂ at 0°, had an ee of only 30%. With other ligands, diazomalonate 6b reacted with a lower enantioselectivity than ylide 7b , however. The intramolecular cyclopropanation of the acetoacetate‐derived phenyliodonium ylide 15b afforded 16b with 68% ee with ligand Xa , but the corresponding diazo compound was unreactive when exposed to chiral copper catalysts. The observation of asymmetric induction in the Cu‐catalyzed reactions of the ylides 7 and 15 is consistent with a carbenoid mechanism; however, the discrepancy of the enantioselectivities observed between diazomalonate 6b and ylide 7b suggests a competing unselective pathway for cyclopropanation outside of the coordination sphere of copper.     

Comprehensive Analysis of Fragment Orbital Interactions to Build Highly π‐Conjugated Thienylene‐Substituted Phenylene Oligomers

π‐Conjugated thienylene? phenylene oligomers with fluorinated and dialkoxylated phenylene fragments have been designed and prepared to understand the interactions in fragment orbitals, the influence of the substituents (F, OMe) on the HOMO–LUMO gap, and the role of intramolecular non‐covalent cumulative interactions in the construction of π‐conjugated nanostructures. Their strong conjugation was also evidenced in the gas phase by UV photoelectron spectroscopy and theoretical calculations. These results can be explained by the crucial role of the relative energetic positions of the π orbitals of the dimethoxyphenylene, which was used to model the dialkoxyphenylene entity, in determining the π/π^* orbital levels of the fluorinated phenylene entity. Dialkoxyphenylenes raise the HOMO orbitals, whereas fluorinated phenylenes lower the LUMO orbitals in the oligomers. In addition, the presence of S???F and H???F interactions in the fluorinated phenylene? thienylene compounds add to the S???O interactions in the mixed targets and contribute to the full conjugation in the oligomer, inducing weak inter‐ring angles between the involved aromatic cycles. These results, which showed extended conjugation of the π system, were corroborated by a narrow HOMO–LUMO gap (according to DFT calculations) and by a relatively strong maximum wavelength (as obtained by TD‐DFT calculations and experimental UV/Vis measurements). The crystallographic data of two mixed thienylene? (fluorinated and dialkoxylated phenylene) five‐ring oligomers agree with the above results and show the formation of quasi‐planar conformations with non‐covalent S???O, H???F, and S???F interactions. These studies in the solid and gas phases show the relevance of associating dialkoxyphenylene and fluorinated phenylene fragments with thiophene to lead to oligomers with improved electronic delocalization for electronic or optoelectronic devices.