Fluoroboric Acid Adsorbed on Silica-Gel–Catalyzed Synthesis of 14-Aryl-14H-dibenzo[a,j]xanthene Derivatives

A simple and efficient procedure has been developed for the preparation of 14-aryl-14H-dibenzo[a,j]xanthene derivatives using fluoroboric acid adsorbed on silica gel as a heterogeneous catalyst. The methodology involves the one-pot condensation reaction of β-naphthol and aryl aldehydes under solvent-free conventional heating conditions. The present approach offers several advantages such as shorter reaction times, simple work-up, excellent yields, low cost, and mild reaction conditions. The catalyst is easily recoverable and reusable without loss of its catalytic activity.     

Green Approaches for the Synthesis of 12-Aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones in Aqueous Media and Under Microwave Irradiation in Solventless Conditions

Convenient and environmentally benign procedures have been reported for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one derivatives by multi component condensation reactions of aromatic aldehydes with β-naphthol and cyclic 1,3-dicarbonyl compounds, namely, dimedone and cyclohexane-1,3-dione. The three-component condensation has been successfully achieved in one pot by refluxing the components in water and is efficiently catalyzed by sulfuric acid. The condensation has also been achieved by irradiating the components in the presence of a catalytic amount of para-toluene sulfonic acid under neat conditions with microwaves. The green methodologies defined herein avoid the severe conditions posed by the older existing methods and prove to be efficient in terms of good yields, operational simplicity, easy workup, and short reaction time.     

Iodine-Catalyzed Synthesis of 12-Aryl-8,9,10,12-tetrahydro-benzo[a]xanthen-11-one Derivatives via Multicomponent Reaction

Iodine efficiently catalyzes the one-pot, three-component reaction of aryl aldehyde, 2-naphthol, and cyclic 1,3-dicarbonyl compound under solvent-free conventional heating conditions to afford the corresponding 12-aryl-8,9,10,12-tetrahydro-benzo[a]xanthen-11-one derivatives. The present approach offers several advantages such as shorter reaction times, good yields, low cost, and mild reaction conditions.     

New Organosoluble and Optically Transparent Polyamides Containing Xanthene Units and Methyl Pendant Groups From 9,9-Bis[4-(4-carboxyphenoxy)-3-methylphenyl]xanthene

A new aromatic dicarboxylic acid, 9,9-bis[4-(4-carboxyphenoxy)-3-methylphenyl]xanthene (BCAMPX) was prepared from the nucleophilic substitution reaction of 9,9-bis(4-hydroxy-3-methylphenyl)xanthene with p-fluorobenzonitrile, followed by alkaline hydrolysis. Then BCAMPX was polycondensated with various aromatic diamines to afford the polyamides with the number-average molecular weight in the range of 45,300–51,500 and the polydispersity index ranged from 1.67 to 1.85. These polyamides showed glass transition temperatures between 260–286°C and 10% weight loss temperatures ranging from 490 to 504°C and 480 to 490°C in nitrogen and air respectively, and char yields above 52% at 800°C in nitrogen. Nearly all polyamides were readily soluble polar aprotic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc), tetrahydrofuran and pyridine, and afforded transparent, strong and flexible films upon casting from DMAc solvent. All polyamides were amorphous and exhibited tensile strengths of 80–91 MPa, elongations at break of 9–13%, and initial moduli of 1.95–2.82 GPa, as well as low moisture absorption in the range of 2.65–3.65%, and high transparency with an ultraviolet–visible absorption cut-off wavelength in the 360–378 nm range.     

Iodine Catalyzed Microwave-Assisted Synthesis of 14-Aryl（Alkyl）-14H-dibenzo[a,j]xanthenes

A straightforward and effective procedure for the synthesis of 14-aryl（alkyl）-14H-dibenzo[aj]xanthenes was described using a catalytic amount of molecular iodine under microwave irradiation to afford the corresponding xanthenes in good yields.     

一种含三氟甲基和呫吨结构聚酰胺的合成与性能

在浓硫酸和3-巯基丙酸催化下,3′-三氟甲基苯基-2,2,2-三氟苯乙酮(1)和甲苯于40～50℃下缩合反应8 h,制得中间体-1,1-二(4-甲基苯基)-1-(3′-三氟甲基苯基)-2,2,2-三氟甲基乙烷(2),继而在光照和N-溴代丁二酰亚胺促进下,将中间体氧化得到二羧酸-1,1-二(4-羧基苯基)-1-(3′-三氟甲基苯基)-2,2,2-三氟甲基乙烷(3),二步反应总收率为77.4%.采用Yamazaki体系,3和9,9-二[(4-氨基苯氧基)苯基]呫吨进行溶液亲核缩聚反应,制得了一种高分子量的(数均分子量为43000,分子量分布为1.8)新型含三氟甲基和呫吨结构的聚酰胺.该聚酰胺为非晶态结构并具有良好的透光率(λcutoff=330 nm),其玻璃化转变温度(Tg)为242℃,在氮气气氛中5%的热失重温度(Td5)为465℃,800℃时的残炭率为50%.聚合物易溶于N,N-二甲基乙酰胺(DMAc)、N-甲基吡咯烷酮(NMP)、间甲酚、吡啶(Py)和四氢呋喃(THF)等有机溶剂中,并可浇注得到韧性好和透明的薄膜,其拉伸强度为85 MPa,拉伸模量为2.0 GPa,断裂伸长率为10%.同时,该聚合物的体积电阻、表面电阻和介电常数分别为2.85×1015Ωcm,4.23×1014Ω和3.55(100 Hz),呈现了良好的电绝缘性能.     

Cyclo-Ketal Xanthene Dyes: A New Class of Near-Infrared Fluorophores for Super-Resolution Imaging of Live Cells

Newly emerging super-resolution imaging techniques provide opportunities for precise observations on cellular microstructures. However, they also impose severe demands on fluorophores. Here, we develop a new series of NIR xanthene dyes, named as KRh s, by replacing the 10-position O of rhodamines with a cyclo-ketal. KRh s display an intense NIR emission peak at 700 nm with fluorescence quantum yields up to 0.64. More importantly, they, without the aid of enhancing buffer, exhibit stochastic fluorescence off–on switches to support time-resolved localization of single fluorophore. KRh s are functionalized into KRh-MitoFix , KRh-Mem and KRh-Halo that demonstrate mitochondria, plasma membrane and fusion protein targeting ability, respectively. Consequently, these KRh probes demonstrate straightforward usage for super-resolution imaging of these targets in live cells. Therefore, KRh s merit future development for fluorescence labeling and super-resolution imaging in the NIR region.     

A Xanthene-Based Mono-Anionic PON Ligand: Exploiting a Bulky,Electronically Unsymmetrical Donor in Main Group Chemistry

The synthesis of a novel mono-anionic phosphino-amide ligand based on a xanthene backbone is reported, togetherr with the corresponding Ga^I complex, (PON)Ga (PON = 4-(di(2,4,6-trimethylphenyl)phosphino)-5-(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene). The solid-state structure of (PON)Ga (obtained from X-ray crystallography) reveals very weak O⋅⋅⋅Ga and P⋅⋅⋅Ga interactions, consistent with a R₂NGa fragment which closely resembles those found in one-coordinate amidogallium systems. Strong N-to-Ga π donation from the amido substituent is reflected in a very short N−Ga distance (1.961(2) Å), while the P⋅⋅⋅Ga contact (3.076(1) Å) is well outside the sum of the respective covalent radii. While the donor properties of the PON ligand towards Ga^I are highly unsymmetrical, oxidation to Ga^III leads to much stronger coordination of the pendant phosphine as shown by P−Ga distances which are up to 20 % shorter. From a steric perspective, the PON ligand is shown to be significantly bulkier than related β-diketiminate systems, a finding consistent with reactions of (PON)Ga towards O-atom sources that proceed without oligomerization. Despite this, the enhanced P-donor properties brought about by oxidation at gallium are not sufficient to quench the reactivity of the highly polar Ga−O unit. Instead, intramolecular benzylic C−H activation is observed across the Ga−O bond of a transient gallanone intermediate.     

2个含呫吨结构双酚化合物的合成

以呫吨酮为原料,经二氯亚砜氯化得到9,9-二氯呫吨中间体,无需分离纯化,将其分别与邻甲酚和2,6-二甲基苯酚进行取代反应,制得2个含呫吨结构的双酚化合物9,9-二(4-羟基-3-甲基苯基)呫吨和9,9-二(4-羟基-3,5-二甲基苯基) 呫吨,产率分别为81.0%和80.5%。 用FTIR、1H NMR、13C NMR和元素分析对其组成和结构进行了表征。 该法具有操作简单、反应条件温和及收率高等优点。