Zeolitic imidazolate framework 8 (ZIF‐8) reinforced macroporous resin D101 for selective solid‐phase extraction of 1‐naphthol and 2‐naphthol from phenol compounds

Macroporous resin has been attracting intensive attention due to its critical role in separation and purification of natural products. Herein, a zeolitic imidazolate framework 8 reinforced macroporous resin D101 was prepared via a room temperature growth method and used for dispersive SPE of 1‐naphthol and 2‐naphthol. The parameters affecting the adsorption and desorption efficiency such as the sample pH, adsorbent amount, extraction time, desorption solvent, and desorption time were investigated. The as‐prepared adsorbent showed selectivity for 1‐naphthol and 2‐naphthol compared to other phenols. Under the optimum dispersive SPE conditions, the detection of 1‐naphthol and 2‐naphthol coupled with a CZE method was conducted and the LODs for 1‐naphthol and 2‐naphthol were 1.37 and 1.43 ng/mL, respectively. Moreover, the results of urine sample analysis showed the spiked recoveries to be in the range of 96.2–106.9%. This study indicated that D101@ZIF‐8 (where ZIF is zeolitic imidazolate framework) is a promising selective adsorbent for the analysis of 1‐naphthol and 2‐naphthol in urine samples.     

l-Hexanesulphonic acid sodium salt promoted the one-pot synthesis of amidoalkyl naphthols under microwave-irradiation

Amidoalkyl naphthols have been synthesized in high yields in the presence of 1-hexanesulphonic acid sodium salt as an inexpensive solid catalyst under solvent-free conditions and microwave-irradiation.This catalyst provides clean conversion;greater selectivity and easy workup make this protocol practical and economically attractive.     

Cascade reaction of 2,3-naphthalenediol with benzene in the presence of aluminum halides

2,3-Naphthalenediol on superelectrophilic activation with aluminium halides smoothly reacts with benzene to give 4-((3-phenyl-1H-inden-1-yl)methyl)benzene-1,2-diol, which in turn undergoes intramolecular cyclization to form 5,10-methano-5-phenyldibenzo[a,d]cycloheptane-2,3-diol. The mechanistic aspects of these unusual transformations are discussed.     

Gold-catalyzed chemoselective formal (3+2)-Annulation reaction between β-naphthols and methyl aryldiazoacetate

A chemoselective domino annulation reaction of β-naphthols with methyl aryldiazoacetate is described. The gold catalyst promoted C–H functionalization of β-naphthols, whereas a rhodium or copper complex led to O–H insertion reactions. Consecutive intramolecular lactonization occurred after site-selective alkylation at the 1-position of β-naphthol, providing functionalized naphthofuranone derivatives. The product was transformed into a chiral molecule bearing an all-carbon quaternary stereogenic center with high enantioselectivity.     

1H-NMR investigations of the conformation of aryl-(hydroxynaphthyl)-methylpiperidines. Intramolecular interactions,IV

Summary The¹H-NMR spectra of aryl-(hydroxynaphthyl)-methylpiperidines, which are model compounds for intramolecular hydrogen bonding, have been analyzed in order to investigate their conformations in solution. As dynamic phenomena can be assumed from line broadening, low temperature spectra have been measured to evaluate the coalescence temperatures and the energy barriers. The latter have been discussed with respect to the size and position of selected substituents. It can be shown that the molecules exist in one energetically favorable conformation with the aryl ring perpendicular to the plane of the naphthol ring system. The interaction between the naphthol ring and the aryl ring influences the conformation at the piperidine ring moiety. This effect leads to an increase of the inversion barrier of the piperidine residue.On Sabbatical Leave from Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan     

Enzymatic glucosylation of unnatural naphthols by a promiscuous glycosyltransferase from Aloe arborescens

Enzymatic glucosylation of unnatural products by natural glycosyltransferases (GTs) has great potential in creating novel and bioactive glucosides. A new GT (AaGT3) from Aloe arborescens exhibited catalytic promiscuity and high efficiency to diverse unnatural naphthols. By combing the substrate flexibility and catalytic reversibility of AaGT3, a cost-effective enzymatic approach to novel and bioactive unnatural glucosides was established. These studies indicate the significant potential of promiscuous natural GTs in synthesis of unnatural bioactive glucosides in drug discovery.     

Efficient one-pot synthesis of benzopyranobenzopyrans and naphthopyranobenzopyrans by domino aldol-type reaction/hetero Diels-Alder reaction of resorcinols and naphthols

The efficient one-pot synthetic approaches for benzopyranobenzopyrans and naphthopyranobenzopyrans are described. The key strategies involve ethylenediamine diacetate-catalyzed cyclization by domino aldol-type reaction/hetero Diels-Alder reaction of resorcinols and naphthols to benzaldehydes with O-allyl ether groups. These reactions provide a rapid route for the synthesis of novel types of polyheterocycles with stereochemically defined quaternary carbon centers.     

Reactivity of electrochemically generated radical cations of alkylnaphthalenes interpreted by AM1 calculations

Electro-oxidations of alkylnaphthalenes lead mainly to polymeric products and show a radical cation mechanism. Mechanisms are proposed and discussed based on energetic arguments. Enthalpies of formation and the energies of the HOMO and SOMO, calculated using the AM1 program, are presented. It is shown that the prevailing polymeric products are obtained by way of the intermediate formation of naphthols.     

The regioselective synthesis of monomethoxynaphthylene diacetates

Methods for the conversion of 1,4,5-naphthalenetriols into the corresponding monomethoxy diacetates are described. All utilise the formation of peri-bridged intermediates.     

Syntheses of Substituted Naphthalenes and Naphthols

Syntheses of substituted naphthalenes and naphthols are described. Based on Claisen rearrangement, ring‐closing metathesis (RCM), and related reactions, isovanillin was successfully transformed into a series of substituted naphthalenes and naphthols with good overall yields.