Second-derivative constant-wavelength synchronous scan spectrofluorimetry for determination of benzo[b]fluoranthene, benzo[a]pyrene and indeno[1,2,3-cd]pyrene in drinking water

The use of derivative constant-wavelength synchronous scan fluorimetry is reported for the determination of three polycyclic aromatic hydrocarbon pollutants in drinking water (linearity range 0.4-4 mug 1(-1)). The limits of detection (LD) and quantification (LQ) (mug 1(-1)) are 0.01 and 0.07 for benzo[b]fluoranthene, 0.03 and 0.12 for benzo[a]pyrene and 0.19 and 0.57 for indeno[1,2,3-cd]pyrene in the presence of three other pollutants, benzo[k]fluoranthene, benzo[ghi]perylene and fluoranthene. The precision (RSD /= 85%) were satisfactory.     

General synthetic route to benz[g]isoquinolines (2-azaanthracenes)

Benzylic zinc reagents add with high regioselectivity to 1-(phenoxycarbonyl) salts derived from pyridine-3-carboxaldehyde ( 1a ) or 3-acetylpyridine ( 1b ) to yield 1-(phenoxylcarbonyl)-4-benzyl-1,4-dihydropyridine-3-carboxaldehydes 5a, 5c or ketones 5b, 5d . Aromatizations of these dihydro analogues with sulfur led to the corresponding aldehydes 6a, 6c or ketones 6b, 6d . An alternate synthesis to the aldehydic precursors involved additions of benzylic zinc reagents to 1-(phenoxycarbonyl) salts formed from methyl nicotinates which led to the corresponding methyl 1-(phenoxycarbonyl)-4-benzyl-1,4-dihydronicotinates 7a, 7b . Aromatizations of 7a, 7b led to the corresponding pyridine esters 8a, 8b which on reduction with lithium aluminum hydride yielded the corresponding carbinols 9a, 9b . Oxidation of 9a, 9b by manganese dioxide afforded aldehydes 6e, 6f . Aldehydes 6a-f were readily converted into the benz[g]isoquinolines 10a-f on heating in polyphosphoric acid.     

A novel approach to benz[e]indenes

A number of benz[e]indene derivatives have been prepared at room temperature in good to excellent yields by treating 3-(2-formyl-cycloalkenyl)-acrylic acid esters with diphosphorus pentasulfide. An azulene derivative was also synthesized by this simple method.     

Direct, two-step synthetic pathway to novel dibenzo[a,c]phenanthridines

Novel dibenzo[a,c]phenanthridines are prepared regioselectively by the application of a straightforward synthetic pathway, starting from new 3,4-diaryl- and 3,4-dihydro-3,4-diarylisoquinolines prepared via Ritter-type heterocyclization and the more classical two-step reductive amination/Bischler-Napieralski cyclization of triarylethanones, respectively. A comparative study of nonphenolic oxidative coupling methodologies provides a highly efficient procedure, based on the hypervalent iodine reagent phenyliodine(III) bis(trifluoroacetate) (PIFA), to accomplish the final coupling step.     

Synthetic routes to 2-(2-benzofuranyl)benzoic acids and their cyclization into benz[6]indeno[2,1-d]furan-10-ones

The benz[6]indeno[2,1-d]furan-10-ones 1 were prepared by the intramolecular cyclization of the 2-(2-benzofuranyl)benzoic acids, 2 , the unequivocal routes to which are described herein. Various synthetic methods to these acids were tested, as well as the methods to cyclize them.     

A novel synthesis route to furo[3,2-a]carbazole

In this paper,we report a novel approach to the heteroaryl-condensed nuclei of natural furo[3,2-a]carbazole alkaloids.Our synthetic studies use N-phthaloyl tryptophan methyl ester as starting material and zinc ion mediated transamination reaction as the key step.This work also implicated a novel strategy to assemble other [a]-fused carbazoles.     

A novel synthetic route to 6-oxabicyclo[3.1.1]heptane skeleton

6-Oxabicyclo[3.1.1]heptane skeleton is synthesized starting from bicyclo[2.2.1]heptane skeleton, in which as a key reaction, Baeyer-Villiger oxidation of the tricyclic oxetane (19) is involved.     

A novel synthesis of dibenzo[b,f] [1,4]thiazepin-11(10H)one 5,5-dioxides

Treatment of thioxanthen-9-one 10,10-dioxides with sodium amide in liquid ammonia provided a novel one-step conversion to dibenzo[b,f][1,4]thiazepin-11(10H)one 5,5-dioxides. Some limitations and a possible mechanism for the reaction are discussed.     

Gold-catalyzed cycloisomerization of 1,7-diyne benzoates to indeno[1,2-c]azepines and azabicyclo[4.2.0]octa-1(8),5-dines

A synthetic method that relies on Au(I)-catalyzed cycloisomerization reactions of 1,7-diyne benzoates to prepare indeno[1,2-c]azepines and azabicyclo[4.2.0]octa-1(8),5-dines is described.     

A new route to pyrimido[1,6‐a]benzimidazole derivatives

Cyclocondensation of orthophenylendiamines with 3‐bromopropionic acid in PPA afforded 2‐vinylbenzimidazoles which were subsequently converted to their corresponding 2‐(1,2‐dibromoethyl)‐1H‐benzimidazoles on treatment with bromine. Reaction of these compounds with aryl nitriles or aryl isocyanates in basic chloroform yielded 1‐arylpyrimido[1,6‐a]benzimidazoles and 2‐arylpyrimido[1,6‐a]‐benzimidazol‐3‐ones respectively.     

Simple route to indeno[1, 2-b]quinoline derivatives via a coupling reaction catalyzed by TiO2 nanoparticles

A simple,efficient and high yielding approach for the synthesis of indeno[1,2-b]quinolinediones has been developed by a one-pot,four-component,coupling reaction utilizing TiO₂ nanoparticles（TiO₂-NPs） as a heterogeneous catalyst at 80℃in aqueous media.     

N,N,5-trimethyl-1H-benzothiopyrano[4,3,2-cd]-indazole-1-ethanamine — A novel heterocycle

Treatment of thioxanthenone 6 with N-(2-dimethylaminoethyl)hydrazine led to the benzothiopyranoin-dazole 3 , a novel heterocycle, along with the expected compound 8 .