Free Naphthols Research Articles

Photoresponsive spiro-polymers generated in situ by C\u2013H-activated polyspiroannulation

The development of facile and efficient polymerizations toward functional polymers with unique structures and attractive properties is of great academic and industrial significance. Here we develop a straightforward C–H-activated polyspiroannulation route to in situ generate photoresponsive spiro-polymers with complex structures. The palladium(II)-catalyzed stepwise polyspiroannulations of free naphthols and internal diynes proceed efficiently in dimethylsulfoxide at 120 °C without the constraint of apparent stoichiometric balance in monomers. A series of functional polymers with multisubstituted spiro-segments and absolute molecular weights of up to 39,000 are produced in high yields (up to 99%). The obtained spiro-polymers can be readily fabricated into different well-resolved fluorescent photopatterns with both turn-off and turn-on modes based on their photoinduced fluorescence change. Taking advantage of their photoresponsive refractive index, we successfully apply the polymer thin films in integrated silicon photonics techniques and achieve the permanent modification of resonance wavelengths of microring resonators by UV irradiation.

Facile preparation of naphthol AS-based fluorescent probe for highly selective detection of cysteine in aqueous solution and its imaging application in living cells

A simple and new fluorescent probe (1) for selective detection of cysteine (Cys) in aqueous solution was facilely synthesized. It was developed based on the masking the phenolic OH group in naphthol AS by a methacrylate group, where the methacrylate group acts as an electron acceptor to quench fluorescence of naphthol AS as well as a reactive site for Cys. The conjugate addition/cyclization reaction of Cys toward methacrylate moiety in the probe 1 led to a cleavage of the methacrylate group and release of free naphthol AS, thereby induced a significant enhancement of fluorescence. The present fluorescent probe exhibited high selectivity toward Cys over homocysteine (Hcy) and glutathione (GSH) and worked well in a physiological aqueous medium, allowing a successful application in living cells imaging.

ChemInform Abstract: Palladium(II)‐Catalyzed Oxidative Dearomatization of Free Naphthols with Two Alkyne Units.

AbstractThe novel [2+2+1] spiroannulation reaction of naphthols with alkynes succeeds using symmetrical diaryl and dialkyl alkynes.Mixed aryl‐alkyl alkynes provide three regioisomeric products one of which is formed with moderate to good excess (not shown).

Palladium(II)-catalyzed oxidative dearomatization of free naphthols with two alkyne units.

Readily available 2-naphthols undergo [2 + 2 + 1] spiroannulation reactions with alkynes in the presence of a Pd(II) catalyst and an oxidant. This process relies on C-H functionalization and naphthyl ring dearomatization at the 1-position of 2-naphthols to provide a variety of spirocyclic compounds. Using alkyl-aryl alkynes as the coupling partners led to regioisomeric mixtures in favor of the head-to-tail isomer bearing a quaternary carbon stereocenter.

Copper-Catalysed Asymmetric 1,4-Addition of Organozinc Compounds to Linear Aliphatic Enones Using 2,2′-Dihydroxy 3,3′-Dithioether Derivatives of 1,1′-Binaphthalene

Directed ortho dilithiation of bis(diethylcarbamate) or bis(MOM)-protected (Sa)-1,1′-bi(2-naphthol) followed by treatment with R2S2 [R = Me, Ph (X-ray structure)] or Me2Se2 cleanly affords the 3,3′ derivatives; the free naphthols are produced on deprotection. In the case of the bis(MOM) series, but not that of the bis(carbamates), some racemisation occurs. The ligand 2,2′-dihydroxy-3,3′-dimethylthio-1,1′-binaphthalene shows optimal performance in the addition of ZnEt2 to linear aliphatic enones (E)-R1C(O)CH=CHR2. Variation of the steric demands of R1 and R2 generates catalytic results consistent with binding of a zinc-based Lewis acid anti to the ene function and with the reactive conformation being s-cis. With enones containing the functions R2 = (CH2)nCH(OAlkyl)2 (n = 0−2), the ZnEt2 addition products undergo base-promoted cyclisation.

The oxidative cross-coupling of substituted 2-naphthols, part I: The scope and limitations

Highly selective oxidative cross-coupling of differently substituted 2-naphthols mediated by Cu(II)-tert-butyl amine complexes is described. The “cross”-products are obtained in good to excellent yields and the selectivity up to ⪢90% is observed depending on the substitution of naphthol nuclei. The alternative procedures - the cross-coupling of free naphthols with CuCl(OMe) as well as the coupling of sodium naphtholates with anhydrous copper(II) chloride - were also studied. All these methods enable a simple and high-yield access to the unsymmetrically substituted binaphthols. A successful optical resolution of methyl 2,2′-dihydroxy-1,1′-binaphthalene-3-carboxylate by means of liquid chromatography on triacetyl-cellulose and the subsequent configurational correlation with a binaphthol derivative of known absolute configuration is reported.

Potentiometric titration of some naphthyl hydrogen sulphates and naphthyl dihydrogen phosphates

A rapid potentiometric titration of acid esters of naphthyl phosphates and sulphates based on acid-base properties of individual esters and their salts is described, and the values for their dissociation constants have been determined. Naphthyl dihydrogen phosphates and naphthyl hydrogen sulphates behave generally as di- and monobasic substances. Use of the proposed method, if combined with the determination of free naphthol and inorganic phosphates or sulphates, enables detailed analysis of such esters to be carried out.

Histochemical demonstration of acid phosphatase by an improved azo-dye method.

Histochemical demonstration of acid phosphatase by an azo-coupling procedure has been investigated and conditions established whereby acceptable histological localisations without evidence of diffusion artefact may be secured. These include catalysis of the coupling reaction and retarding of the rate of enzymic liberation of free naphthol. More rapid coupling is achieved in a medium of pH 5.5-pH 6.0 by the use of a high concentration of diazonium salt, by incubation at 37°C. and by the presence of a quinoline derivative, percain. Liberation of free naphthol occurs relatively slowly at the non-optimal pH range employed and is further restricted by lowering of substrate concentration; in this manner local overloading of the coupling system at sites of high enzyme activity is avoided, with consequent avoidance of diffusion of free naphthol prior to coupling. The dye produced is of a highly contrasting color and its insolubility in ethanol and xylol enables the mounting of tissues in synthetic media. The procedure is applicable to both Formalin and acetone fixed tissues, either frozen sections or paraffin ribbons, adequate pigment deposition being achieved after incubation periods of 15-120 minutes.