86,571 research outputs found
Synthesis of pyrano[2,3-f] chromen-2-ones vs. pyrano[3,2-g] chromen-2-ones through site controlled gold-catalyzed annulations
No full textRegioselective access to 10-substituted-2H,8H-pyrano[2,3-f]chromen-2-ones through the gold-catalyzed intramolecular hydroarylation of readily available 7-(prop-2-yn-1-yloxy)-2H-chromen-2-one derivatives at their C-8 congested position was investigated by tuning the electronic and steric properties of the ligand on the gold complex. On the other hand, the combination of the JohnPhosAu(MeCN)SbF6 catalyzed intramolecular hydroarylation of 8-iodo-7-(prop-2-yn-1-yloxy)-2H-chromen-2-one derivatives followed by selective palladium/formate C-I reduction allows for the exclusive formation of 2H,8H-pyrano[3,2-g]chromen-2-one regioisomers. The development of these two protocols provides versatile synthetic tools required for exploring the biological activities of these new pyranocoumarin derivatives
Transition Metals Catalysis in C-C and C-Heteroatom Bonds Forming Reactions
No full textTransition metals catalysis represents an important and
versatile tool for the organic synthesis. Indeed its use is associated
with several advantages in terms of reaction selectivity, and
“atom economy”. In the last decade the growing utilization of
transition metals catalysis has deeply influenced and modified the
design of heterocyclic synthesis as testified by the wide amount
of studies on the palladium-catalyzed cross-coupling reaction that
in 2010 led Prof. Richard F. Heck (University of Delaware,
USA), Prof. Ei-ichi Negishi (Purdue University, USA) and Prof.
Akira Suzuki (Hokkaido University, Japan) to achieve the Nobel
Prize for Chemistry.
In this context, during my doctorate activity, we investigated the
construction of heterocyclic rings and the production of
derivatives of heterocyclic compounds of biological interest
through palladium, copper and gold catalyzed reactions.
As part of our studies on the palladium catalysis we developed
several synthetic strategy for the construction of different classes
of compounds such us functionalized 2,3-dihydrofurans,
substituted 2,3-substituted quinolin-4-(1H)-ones,
dibenzo[a,c]carbazoles, 2-amino ketones and aryl sulfones. Then,
the economic attractiveness of copper-based methods and the
growing interest in copper-catalyzed syntheses stimulated us to
investigate some copper-catalyzed protocol. In this area we
studied the oxidation reaction of the 1,2-diarylethanones and the
cyclization reaction of the N-(2-bromoaryl)enaminones to obtain
2,4-diarylbenzo[b][1,4]oxazepines. Finally, using gold complexes
we developed a new sinthetical approach to 2,4-diaryl-2,3-
dihydro-1H-benzo[b][1,4]diazepines
Synthesis of indolo[1,2-c]quinazolines from 2-alkynylaniline derivatives through Pd-catalyzed indole formation/cyclization with N,N-dimethylformamide dimethyl acetal
No full textAn efficient strategy for the synthesis of 6-unsubstituted indolo[1,2-c]quinazolines is described. The Pd-catalyzed reaction of o-(o-aminophenylethynyl) trifluoroacetanilides with Ar-B(OH)2 afforded 2-(o-aminophenyl)-3-arylindoles, that were converted to 12-arylindolo[1,2-c]quinazolines by adding dimethylformamide dimethyl acetal (DMFDMA) to the reaction mixture after extractive work-up. This reaction outcome is different from the previously reported Pd-catalyzed sequential reaction of the same substrates with Ar-I, Ar-Br and ArN2+BF4-, that afforded 12-arylindolo[1,2-c]quinazolin-6(5H)-ones. Moreover, 12-unsubstituted indolo[1,2-c]quinazolines can be obtained both by reacting 2-(o-aminophenyl)indoles with DMFDMA or by sequential Pd-catalyzed reaction of o-(o-aminophenylethynyl)aniline with DMFDMA
The pyrrole methodology for the sustainable functionalization of graphene layers
No full textGraphene, a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice, has
emerged as one of the most promising materials with exceptional electrical, mechanical, and thermal
properties. However, to fully unlock its potential, it is crucial to obtain graphene in its exfoliated form,
consisting of a few layers or even single layers.
The importance of obtaining graphene lies in its enhanced properties compared to graphite: fewlayered
graphene exhibits increased reactivity and accessibility of active sites, crucial for catalytic
applications [1] such as fuel cells, water splitting, and chemical sensing. Additionally, in composite
materials, exfoliated graphene serves as a reinforcing agent [2], imparting superior mechanical
strength and electrical conductivity [3].
Several methods have been developed to obtain few layers graphene [4]: from bulk graphite,
known as top-down approach (such as mechanical exfoliation or chemical methods), or synthesizing
it directly in its exfoliated form, the so-called bottom-up strategy (like molecular assembly or epitaxial
growth).
An interesting and accessible approach to obtaining few layers graphene has been recently
developed. The pyrrole methodology is characterized by the easy insertion of organic moieties on
graphene defects. It is performed by using two approaches: i) mechanical, such as the application
of high shear force using a Silverson-type mixer, and ii) chemical, namely the modification of
graphene sheets to prevent re-stacking [5-6].
In this contribution, the decoration of graphene flakes with different pyrrole derivatives is reported,
along with their full characterization.
The results obtained confirm the modification of graphene flakes. The conducted tests indicate a
Diels-Alder type grafting reaction of the flakes. However, our primary focus lies on the pyrroles,
which, upon oxidation, demonstrate a propensity to act as dienophiles.
References
[1] V. B. Mbayachi, et al., Results Chem, 3, (2021), 100163.
[2] G. Prioglio, et al., Polymers 12(4), (2020), 944.
[3] P. Bøggild, et al., 2D mater, 4(4), (2017), 042003.
[4] S. S. Shams, et al., Mater Sci Pol, 33(3), (2015), 566–578.
[5] V. Barbera, et al., Pure Appl. Chem, 90(2), (2018), 253–270.
[6] V. Barbera, et al., Nanomater, 9(1), (2019), 44
In-Depth Chemical Characterization of Punica granatum L. Seed Oil
No full textFruit seeds belonging to the pomegranate cultivar "Granata" were subjected to extraction and oily component analysis, with the aim of obtaining information about their composition. The presence of conjugated isomers of linolenic acid (CLNA isomers) in the oily phase extracted from the seeds gives a high added value to this part of the fruit, which is too often considered and treated as waste. The separated seeds were subjected to a classic Soxhlet extraction with n-hexane or extraction with supercritical CO2, assisted by ethanol. The resulting oils were evaluated by H-1 and C-13-NMR and AP-MALDI-MS techniques. Differences in the triacylglycerols composition, with particular regard to punicic acid and other CLNA content, were studied in depth. Results showed the prevalence of punicic acid in the triacylglycerol mixture up to the 75%, with clear preponderance in the extract by supercritical fluids. Consequently, other CLNA isomers are, altogether, two-fold less represented in the supercritical extract than in the Soxhlet one. The two oily residues were subjected to solid phase extraction (SPE) and to HPLC-DAD analysis for the polyphenolic isolation and characterization. In addition to HPLC analysis, which showed different content and composition, DPPH analysis to evaluate the antiradical potential showed that the extract obtained with supercritical CO2 was much more active
Palladium-Catalyzed C12-Selective Direct Arylation of [1,2- c ]Quinazolin-6(5 H)-ones
No full textA straightforward approach to the synthesis of the challenging 12-arylindolo[1,2- c ]quinazolin-6(5 H)-ones through the palladium-catalyzed direct arylation of N -benzyl and NH-free [1,2- c ]quinazolin-6(5 H)-ones with aryl halides is described
Stereo- and regioselective gold(I)-catalyzed hydroamination of 2-(arylethynyl)pyridines with anilines
No full textThe gold-catalyzed hydroamination of 2-(arylethynyl)pyridines with anilines affords stereoselectively Z-enamine products with excellent regioselectivity. The reaction proceeds with moderate to excellent yields and accommodates a diverse range of functional groups on alkynes (ether, bromo, trifluoromethyl, acetyl, and carbomethoxy) and anilines (ether, bromo, chloro, and carbethoxy). The stereochemistry of the obtained enamines is complementary to that reported in previous studies. A plausible explanation for the observed selectivity was attained by means of NMR experiments
Palladium-Catalyzed Cascade Approach to 12-(Aryl)indolo[1,2- c ]quinazolin-6(5 H)-ones
No full textA straightforward one-pot approach to the synthesis of challenging 12-arylindolo[1,2- c ]quinazolin-6(5 H)-ones is described. Starting from readily available o -(o -aminophenylethynyl)trifluoroacetanilides, palladium-catalyzed aminoarylation of the triple bond with ArI, ArBr, and ArN 2+ BF 4- is followed by cyclization of the resulting N -trifluoroacetyl-2-(o -aminophenyl)-3-aryl indole. This sequential reaction provides the title compounds by means of a rare elimination of trifluoromethane
Palladium-catalyzed Tsuji-Trost-type reaction of benzofuran-2-ylmethyl acetates with nucleophiles
No full textThe palladium-catalyzed benzylic-like nucleophilic substitution of benzofuran-2-ylmethyl acetate with N, S, O and C soft nucleophiles has been investigated. The success of the reaction is dramatically influenced by the choice of catalytic system: with nitrogen based nucleophiles the reaction works well with Pd2(dba)3/dppf, while with sulfur, oxygen and carbo-nucleophiles [Pd(η3-C3H5)Cl]2/XPhos is more efficient. The regiochemical outcome shows that the nucleophilic substitution occurs only on the benzylic position of the η3-(benzofuryl)methyl complex. The high to excellent yields and the simplicity of the experimental procedure make this protocol a versatile synthetic tool for the preparation of 2-substituted benzo[b]furans. This journal i
Eziopatogenesi e manifestazioni cliniche della sindrome di Crouzon: revisione della letteratura
No full textObjectives: The term Craniofacial dysostosis (CFD) is used to describe familiar forms of synostosis involving different sutures of the cranial base and midface. The aim of this work consists in a systematic review of literature on aetiology, etiopathogenesis, epidemiology, diagnosis, clinical, systemic, and oral manifestations and therapeutic options of Crouzon syndrome. Materials and methods: A systematic review of literature through Medline data bank [www.ncbi.nim.nih.gov/pubmed] was done using "Craniofacial Dysostosis", "Craniosynostosis", and "Crouzon Syndrome" as keywords. Results: Crouzon syndrome is the most common craniosynostosis. It develops after an early fusion of superior and posterior sutures of the maxilla with orbital ones, with consequent underdevelopment of the midface and ocular proptosis. Oral manifestations are maxillary hypoplasia, maxillary dental crowding, ogival palatus, and relative mandibular prognathism. Diagnosis can be done either through the evaluation of clinical phenotypes or DNA analysis with polymerase chain reaction (PCR). Treatment is mainly surgical. Orthodontic therapy is performed during the early skeletal maturation. Conclusions: Thanks to the important innovations in surgical techniques and to a muldisciplinary approach, patients affected by this syndrome may aspire to normal cerebral development, physical status, and social relationships
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