Giancarlo Perrini

Cycloadducts of benzonitrile oxide to pyridine. A case of a two-step cycloaddition

Abstract Pyridine adds benzonitrile oxide in apolar solvents, affording fair yields of bisadducts III and IV. Quinoline and isoguinoline afford isolable monocycloadducts VIII and IX.

Cycloadditions of Nitrile Oxides to α,β-Unsaturated Aldehydes. Frontier Orbital Interactions and Secondary Orbital Interactions at Work in Determining Regiochemistry

Abstract The regiochemistry of the cycloadditions of nitrile oxides to crotonaldehyde and cinnamaldehyde has been determined and is dictated by frontier orbital interactions and secondary orbital interactions as well. In cycloadditions to α,β-unsaturated compounds the directive effect of the frontier orbital interactions can be diverted by steric drifts and secondary orbital interactions.

Cycloaddition of benzonitrile oxide to pyridazine, pyrimidine and pyrazine

Abstract Cycloaddition of benzonitrile oxide to pyridazine affords an isolable mono-cycloadduct. In cycloadditions to pyrimidine and pyrazine the primary mono-cycloadducts are labile intermediates which undergo further cycloaddition affording isolable bis- and tris-cycloadducts.

Photodegradation of Anthracene and Benzo[a]anthracene in Polar and Apolar Media: New Pathways of Photodegradation

The photochemical reactions of anthracene and benzo[a]anthracene polycyclic aromatic hydrocarbons (PAHs) in polar and apolar solvents (cyclohexane and water/acetonitrile) were studied using spectroscopic and chromatographic techniques. These homogenous photolysis experiments are used as simplified models to compare PAHs photochemistry in water and oil (or oil films). Moreover, these processes were to some extent used as model in literature in order to study those occurring on particulate matter and aerosol surfaces. In both media, new photochemical reaction products were found. Generally, the reaction rate in the polar medium is faster than that in the apolar medium, and the photodegradation quantum yields increase with increasing polarity of the medium. HPLC-absorption/emission analysis confirmed the literature reports that mainly oxygenated photoproducts, such as PAH-hydroxides, were formed. The novelty of this article is that GC-MS data revealed the presence of new photoproducts that have not yet been described. This simplified model system allowed us to characterize the product distribution, thus simplifying the interpretation of the photodegradation mechanism. The identification of new photofragmentation paths, originating by irradiation of primary PAH photoproducts, may suggest an innovative way of remediation triggered by light.

THE ROLE OF THE HYDROGEN BONDING IN CYCLOADDITIONS OF BENZONITRILE OXIDE WITH CYANOPHENOLS

Abstract The reactivity of aromatic nitriles in cycloadditions with benzonitrile oxide is remarkably enhanced by the ortho-hydroxy substituent. Semiempirical PM3 calculations are in agreement with a hydrogen bonding effect.

The triethylamine catalyzed reaction of N,N-disubstituted thioamide–bromine adducts with unsubstituted thiobenzamide

The reaction of N,N-disubstituted thioamide–bromine adducts with unsubstituted thioamide, followed by treatment with triethylamine, affords novel N′-thiobenzoylamidines along with smaller amounts of secondary products. A mechanism is proposed for the formation of the amidines. The results give an insight into the initial steps of the mechanism by which thioamides are converted into 1,2,4-thiadiazoles.

The PAH and Nitro-PAH Concentration Profiles in Size-Segregated Urban Particulate Matter and Soil in Traffic-Related Sites in Catania, Italy

Polycyclic aromatic hydrocarbons (PAHs) and nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) were identified from both air particulate matter and soils. For air sampling, a six-stage cascade impactor was situated in an urban area (Catania, Italy) that is recognized for its high traffic volume. The soil samples were collected every 1.5 km from under the grass by the side of the median of a Catania road along its full length (8.2 km). HPLC in electrochemical-fluorescence detection mode was used for selective separation, identification and quantification of analytes in air and soil samples, providing both good selectivity and sensitivity. The seasonal trends, effects of urban traffic, and source profiles are discussed herein. Higher PM10 concentrations were observed for summer (43 μg m−3) in comparison to winter (24 μg m−3). Conversely, the PAHs contained in PM10 were higher in winter (0.48 ng m−3 for fluoranthene) than in summer (0.14 ng m−3 for fluoranthene). Analysis of the size-segregated urban particulate matter showed that the amount of PM0.5 (stage 6) was always higher than the amount of other particles (stages 1–5). Furthermore, the PM0.5 was always higher in summer (about 40%, m/m) than in winter (about 30%, m/m). Finally, the amounts of PAH and nitro-PAH in PM0.5 (stage 6) were always higher, by a maximum of one order of magnitude, than that of other particles (stages 1–5). This result is crucial because ultrafine particles have a tendency to move into the blood through the alveolar epithelial barrier. Moreover, the air and soil pollution levels agree with those found in other cities with similar levels of pollution. Supplemental materials are available for this article. Go to the publishers online edition of Polycyclic Aromatic Compounds to view the supplemental file.

1,2-DIHYDRO-2-(4-METHOXYPHENYL)-2-SULPHIDE-1,3,2-DIAZAPHOSPHORIN-4(3H)-THIONES FROM 3-AMINOPROPENENITRILE DERIVATIVES AND LA WESSON'S REAGENT

Abstract The title compounds are obtained from structures incorporating the 3-aminopropenenitrile moiety by treatment with the Lawessons reagent in refluxing toluene.

Spectroscopic Properties of Some Derivatives of Polycyclic Aromatic Hydrocarbons

The aim of this paper is to provide a general picture of the spectral characteristics of some polycyclic aromatic hydrocarbon (PAH) derivatives. A great deal of data concerning PAHs has been reported in the literature, but there is lack of comprehensiveness about important parameters in the same experimental conditions for their nitro (NO2) and amino (NH2) derivatives such as absorption and emission characteristics. Thus, important parameters such as the molar extinction coefficient, absorption maxima, fluorescence maxima, and fluorescence quantum yield are reported here. The efficiencies of the reduction of NO2-PAHs to their corresponding amino compounds were also verified by means of high-performance liquid chromatography (HPLC). This class of derivatives represents one of the most toxic groups of carcinogenic substances and therefore the data reported here should be useful for toxicological research.

1-(dithiolylidene)-1-cyanoacetophenones from dithiolethione-bromine adducts with enaminonitriles

Abstract Title compounds are easily prepared by reaction of dithiolethione-bromine adducts with enaminonitriles followed by treatment with triethylamine. The mechanism that accounts for their formation is discussed.