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Multicomponent Reactions
Full text linkMulticomponent Reactions appear to be ideal for any form of synthesis, because of their numerous advantages in terms of sustainability and selectivity in building up complex molecular architectures, with high molecular diversity. This Special Issue collects seven contributions which expand our knowledge about Multicomponent Reactions, providing a good overview about innovative reactivities and applications
CARTA DELLE GEODIVERSITA’ IN AREE VULCANICHE ALLA SCALA 1:75.000 CON NOTE UILLUSTRATIVE
No full textI vulcani sono sicuramente le manifestazioni più evidenti
della dinamicità della terra. Il territorio su cui insistono
può subire modifiche anche sostanziali in uno spazio
temporale infinitesimo o in tempi più o meno lunghi. Ogni
eruzione comporta l’immissione sulla superficie terrestre
di volumi di materiali da poche decine di m3 fino a km3 con
estensione dei depositi da ettari a centinaia di km2.
Ogni immissione determina l’alterazione del profilo
d’equilibrio dei corsi d’acqua innescando rapidi processi
di erosione, trasporto e sedimentazione di materiale dalle
aree topograficamente più rilevate a quelle più pianeggianti.
Di conseguenza il paesaggio di un’area vulcanica attiva
è soggetto a cambiamenti continui che possono essere più
o meno significativi in funzione della litologia del materiale
vulcanico eruttato. Ad esempio, una colata di lava o un
dicco offre una maggiore resistenza ai processi di erosione
rispetto ad un deposito di cenere non consolidato e quindi la morfologia relativa risulta spesso sollevata
rispetto all’area circostante anche se le lave, al momento
dell’eruzione, tendono a scorrere nelle depressioni topografiche
(inversione del rilievo morfologico).
La grande varietà di materiale eruttato dai vulcani, anche
nel corso di una sola eruzione, determina una ampia varietà
di morfologie che col tempo, quando il vulcano andrà
in estinzione, tenderanno a caratterizzare l’area vulcanica stessa. La diversità dei materiali vulcanici condizionerà lo
sviluppo di biodiversità animale e vegetale e determinerà
anche un diverso adattamento dell’uomo all’ambiente con
ripercussioni sulla tipologia e distribuzione degli insediamenti.La carta della geodiversità in aree vulcaniche ha come
obiettivo proprio quello di evidenziare i diversi litotipi
vulcanici che hanno contribuito in una certa area alla modellazione
del paesaggio ed hanno determinato lo sviluppo
delle attività dell’uomo in funzione delle loro caratteristiche
e fruibilità. La morfologia del territorio ha, infatti,
un’influenza decisiva sulla realtà insediativa e produttiva
dell’uomo e sul sistema faunistico e floristic
DEFORMAZIONI GRAVITATIVE PROFONDE IN AMBIENTE VULCANICO: ESEMPI IN VULCANI ITALIANI
No full textLe aree vulcaniche sono soggette a deformazione verticale lenta o
rapida dovuta ad una instabilità indotta da processi idrotermali o dalla
risorgenza di corpi intrusivi in specifici settori dell’area vulcanica o di
edifici vulcanici. Per di più le aree vulcaniche sono spesso interessate da
sismicità sia a scala regionale che locale. L’instabilità degli edifici vulcanici
si traduce spesso in collassi guidati dalla gravità di parti o dell’intero
fianco dell’edificio vulcanico a cui si associano depositi di frana di volume
considerevole. I processi di collasso si verificano quando l’edificio
vulcanico raggiunge altezze considerevoli, rispetto al suo diametro di base,
e l’accumulo dei materiali prodotti dalle eruzioni causa un sovraccarico
di peso sia sull’edifico stesso che sul substrato su cui poggia l’edificio.
Molti degli aspetti morfologici e strutturali che si sviluppano come conseguenza
dell’instabilità di un vulcano sono simili a quelli osservati in ambiente
sedimentario e generalmente classificati come DGPV (Deformazioni
Gravitative Profonde di Versante). Le strutture più comunemente
associate alla deformazione dell’edifico sono aperture del cratere o delle
caldere a forma di ferro di cavallo a cui spesso sono associati depositi di
colate detritiche di volume significativo.
Molti vulcani italiani, sia attivi che spenti o quiescenti, mostrano crateri
e caldere a forma di ferro di cavallo. Alcune di queste strutture sono
ormai note e ben studiate, mentre altre, per lo più relative ai vulcani più
antichi, sono ancora poco conosciute e in molti casi la loro origine è ancora
dibattuta.
In questo lavoro, dopo un breve excursus sulle strutture di deformazione
più note dei vulcani attivi italiani, come quelle della Sciara del Fuoco
di Stromboli, della Valle del Bove dell’Etna, del Vesuvio e di Ischia,
vengono presentate alcune strutture deformative che mostrano aspetti
comparabili con le DGPV dei vulcani spenti e sottomarini delle Isole
Pontine, del vulcano di Roccamonfina e del vulcano di Panarea.
Nelle Isole Pontine di Ponza e Zannone, le deformazioni gravitative
si sviluppano lungo piani estensionali a basso angolo che, per gli aspetti
morfologici e strutturali osservati, possono essere interpretati come dovuti
a stress locale indotto dall’intrusione del magma che alimentava la crescita
di domi acidi sottomarini. A Ponza, questi piani, lungo cui si realizzava
lo scivolamento gravitativo di masse di ialoclastiti dai fianchi dei domi
in accrescimento, possono essere dovuti alla necessità di creare un
equilibrio tra la progressiva iniezione del magma nella ialoclstite già depositata
e lo stress gravitazionale. A Zannone, la crescita di un criptodomo
portò al basculamento delle unità del basamento sedimentario che
iniziarono a slittare lungo i piani di stratificazione raggiungendo le attuali
posizioni stratigrafiche anomale lungo piani a basso angolo.
A Roccamonfina, nell’Italia meridionale, la presenza della struttura
sommitale calderica aperta verso est a forma di ferro di cavallo può essere
interpretata come dovuta all’instabilità del fianco orientale del vulcano,
sviluppatosi in corrispondenza di un importante elemento strutturale a
carattere regionale (faglia del Monte Massico). Gli aspetti morfologici e
l’entità dei volumi coinvolti nel processo di scivolamento gravitativo, sono
compatibili con quelli delle DGPV.
Infine, a Panarea, nell’ arcipelago delle Isole Eolie, lungo la falesia
occidentale dell’isola, è visibile il nucleo interno del domo lavico. L’esposizione
del cuore del domo suggerisce che il vulcano sia stato soggetto a
una o più fasi di collasso del fianco occidentale. L’analisi dettagliata della
falesia ha evidenziato molti aspetti morfologici generalmente associati alle
deformazioni gravitative profonde di versante (DGPV) ed in particolare a
quelle definite sackungsVolcanic areas are characterized by slow and rapid vertical ground
deformations due to deep thermal instabilities or the resurgence of magma
bodies in delimited sectors of a volcanic edifice. Moreover volcanic
areas are often the loci of both tectonic and volcanic seismicity. For these
reasons, in active or quiescent volcanoes, slope instability is common and
may occur as sector or flank collapses gravitationally controlled, involving
large rock volumes. Volcanoes experience this type of failure when they
reach high relief and oversteepening in a relatively rapid period of activity.
Many morphological and structural features affecting unstable volcanic
edifices subjected to instability are similar to those described as associated
to DGSD (Deep-Seated Gravitational Deformation). The most
common features include horseshoe-shaped craters or calderas and associated
large debris avalanche deposits.
Most of the Italian volcanoes, active, quiescent or dormant, show distinctive
horseshoe-shaped craters opened at one end. Some of them are
well known and studied features, some others have received less attention
due to their state of preservation. For most cases of both categories triggers
and favourable factors are still debated.
This paper presents case studies of slope deformations that may potentially
be classified as DGSD affecting different types of volcanoes and
volcanic islands in Italy
Relatively rapid emplacement of dome-forming magma inferred from strain analyses: the case of the acid Latian dome complexes (Central Italy)
No full textWe have analysed the relationship between the volcanic substratum and magma body emplacement for the acid dome complexes of Latium, Central Italy. Our study shows that the volcanic edifices, which are mainly Pleistocene cryptodomes and related explosive products, were derived from mantle magmas contaminated by crustal materials. The Cimini, Tolfa and Cerite-Manziate dome complexes of Latium show the following characteristics: a shallow laccolith origin; emplacement in basins that have identical tectonic evolution and geological structure; the same magmatic composition and density contrast between magma and host rock; and geochronological data that are inconsistent with field evidence. In the Cimini and Tolfa dome complexes, the deformation induced by shallow intrusions was accompanied by ∼200 m uplift of the sedimentary cover. The estimated pluton infilling time for the Cimini and Tolfa domes is 102 years while the strain rate required to uplift their Pliocene overburden by 200 m is ε'm∼ 10-9 s-1. The rapid evolution of the dome complexes is consistent with field data that show no relevant interruptions in the volcanic activity and no significant compositional changes in the volcanic products related to the extrusion of the domes. For the Cerite-Manziate dome complex, the minimal input rate of magma favoured a monogenetic style of volcanism, independent of the regional stress condition
Structural evolution of the Pleistocene Cimini trachytic volcanic complex (Central Italy)
No full textStructural, geomorphological, geophysical and
volcanological data have been processed for the implementation
of a dedicated GIS through which the structural
evolution of the Pleistocene trachytic Cimini volcano
(central Italy) has been reconstructed. The evolution of the
Cimini complex includes three main close-in time phases:
(1) intrusion of a shallow laccolith, rising along NW and
NE trending faults and stagnating at the contact between
the Mesozoic-Cenozoic and the Pliocene-Pleistocene
sedimentary units constituting the bedrock of the volcano;
(2) emplacement of lava domes along radial and tangential
fractures formed by the swelling induced by the laccolith
growth; (3) ignimbrite eruptions and final effusion of
olivine-latitic lavas. Domes are both of Pelean and low lava
dome type and their morphologywas controlled by the location
on the inclined surface of the swelled area. Some domes
show to have uplifted upper Pliocene thermally metamorphosed
clay sediments, suggesting a cryptodome-like
growth. Comparison of the top of the Mesozoic-Cenozoic
units with the top of the upper Pliocene-Pleistocene sedimentary
complex, suggests that the laccolith emplaced in
a graben of the Mesozoic-Cenozoic sedimentary complex
filled by the Pliocene–Pleistocene sediments uplifted by
the shallow intrusion. Stress patterns acting on the Cimini
area have been deduced analysing the drainage network
and the morphotectonic lineaments. Rose diagrams show
a large dispersion of the lineaments reflecting the local
presence of radial and tangential fractures. The most
frequent extensional NW and NE trending lineaments have
regional significance and controlled th
Evoluzione pleistocenica del margine tirrenico dell'Italia centrale tra eustatismo, vulcanismo e tettonica
No full textViene presentata una sintesi dei dati ottenuti durante la realizzazione dei fogli geologici alla scala 1:50.000 riguardanti alcune aree
costiere del Lazio. La possibilità di porre a confronto l’evoluzione di settori che presentano problematiche simili ma con situazioni
locali specifiche ha permesso di evidenziare, a partire da circa 850 ka, una storia comune per la costa del Lazio settentrionale e centrale,
diversa da quella che ha invece interessato nello stesso intervallo di tempo la costa del Lazio meridionale. La ricostruzione degli
eventi a scala regionale ha permesso di distinguere gli effetti di una tettonica regionale (soprattutto di sollevamento isostatico lungo la
costa del Lazio settentrionale e centrale e di subsidenza per quello meridionale) rispetto a movimenti locali che potrebbero essere
essenzialmente legati alle fasi vulcaniche che hanno contemporaneamente interessato il margine tirrenico del Lazio. Vengono inoltre
evidenziate alcune problematiche che riguardano l’organizzazione cartografica nazionale ed in particolare la denominazione dei sintemi
a scala regionale e la necessità di introdurre una nomenclatura in grado di associare nel suo interno più sintemi non distinguibili sul
terreno.We present a synthesis of the data collected during the field work devoted to the realization of the geological map at the 1:50.000 of
Italy, concerning some coastal areas of Latium. The possibility to compare the evolution of areas envolved in the same geodinamic contest
but having different local structural framework, has allowed us to evidence a common history, starting from 850 ka, for the coast of
northern and central Latium , different from that of the southern coast. The effect of local estensional tectonic related to the volcanism
which interested central Italy in that period was distinguished. The units have been organized in Unconformity Bounded Stratigraphic
Units (UBSU) on the base of the hierarchy order of the basal surfaces delimithing them. Synthemes have been limited by surfaces recognized
at regional scale caused by oscillation of the sea level. Each surface has been dated on the base of the geochronological data
and /or the faunistic content of the above sediments and then it has been correlated to an isotopic stage. The vulcanic units have been
organized following the indication of Fisher and Schmincke (1984), by introducing the Eruption units. “An eruption unit is a deposit defined
as a thickness of volcanic material deposited from an eruptive pulse, an eruptive phase or an eruption...it is a conceptual entity that
relates volcanic activity and a rock stratigraphic unit”. This method allows to consider all the unconformities recognizable in volcanic
areas which cannot be extended at regional scale but are important to reconstruct the main phases of the volcano evolution. It allows
even to consider the volcanic evolution in its regional contest. The volcanic deposits originated by the reworking of the primary units
have been distinguished in syn-eruption and inter-eruption units (Smith, 1991; De Rita et alii, 2002 b; Giordano et alii, 2002 a). The geological
and structural evolution of the island of Ponza, Zannone and Palmarola in the Pontine Archipelago, 30 km south east from the
central coast of Latium, has been reconstructed. These three islands are the remnants of a submarine dome complex developed from
the Upper Pliocene to almost 1.1 Ma. Three main ryolithic domes have been recognized in Ponza, developed along NE-trending lineaments
and showing different hyaloclastic facies reflecting the different geological contest in which they developed. The norhernmost
Piana d’Incenso dome shows a prevailing hyaloclastic facies made of clast supported breccias and by flow banded lavas produced by
its intrusive mode of emplacement, as a cryptodome. Similar facies characterize the Zannone dome in the Zannone island, where the
intrusive nature is demonstrated by the structural relationship between the flow-banded lavas and the sedimentary units: these are tilted
and deformed along low angle normal faults at the contact with the vulcanites. We have interpreted that the domes emplaced as cryptodome,
because they were intruded almost at the center of a structural high of the sedimentary substratum made of the Mesozoic-
Cenozoic brittle rocks. The other domes of Ponza and Palmarola show different hyaloclastic facies, mainly made of thick hyaloclastites
showing different degree of brecciation reflecting the different degree of magma-water interaction. We suggest that the extrusive mode
of emplacement of these domes is because their emplacement was along regional extensional faults controlling the structural evolution
of the continental platform on which the volcanic dome complex developed. In the southern part of Ponza a subaerial trachytic dome
developed almost 1.1 Ma, after that the rhyolitic volcanism ended. The geological gap between the rhyolitic and the trachytic phases of
volcanism, is evidenced by a high relief erosive surface. On the three island, in the range between 80 and 110 m a.s.l., marine terraces
are present. These terraces have been correlated on the base of their similar morphology and because the above sediments are lithologically
similar. They have to be formed after the end of the volcanism in the three islands. The uplifting of the surface occurred probably
during a contemporaneous relative low standing of the sea level. We suggest to relate this event with the uplifting of the central coast of
Latium, that occurred between 0.9 and 0.8 Ma, during the isotopic stage 22, when the alkali-potasssic volcanism started. The difference
of the altitude at which the surface presently lies, is probably due to the effect of local extensional tectonic. Along the northern and the
central coast of Latium, we have recognized three orders of terraces which coincide in the altitude and the age. In the northern coast the
presence of a small basin infilled by volcaniclastic sediments, was helpful in correlating stratigraphic succession of the Vulsini, Sabatini
and Vico volcanic districts to the coastal area successions. Here, the UBSU have been organized in 5 Synthemes whose basal surfaces
were produced during low standing of the sea level. On the base of geochronological data and /or the faunistic content of the above
sediments, the last three synthems have been ascribed to the 9,7 and 5 isotopic stages respectively (De Rita et alii 2002 b). In the central
coast of Italy, in the area of Roma city, the UBSU have been organized in 7 synthemes (Giordano et alii 2003), the last three of which
have the same altitude and age of those recognized along the northern coast. Along the southern coast no terraces can be recognized. It
has been then possible to establish that the coast of central Italy was subjected to a regional uplift evaluated in the order of 0,2 mm/y,
whereas the southern coast was subjected to a continuous subsidence active from Pliocene. Local extensional tectonic related to the
volcanism has been recognized in the roman area. Some problems related to the organization of the national cartography are evidenced.
They concern the nomenclature of synthem at regional scale and the opportunity to introduce a specific hierarchy to indicate an association
of synthemes. In fact, in some cases it has not been possible to recognize all the discontinuities related to sea level oscillations, precluding
the possibility to distinguish single synthemes that have been unified together. They do not represent a supersynthem because
unconformities of major hierachic order were not recognize
Efficient Lewis Acid Systems for the A3 Coupling reaction
No full textEfficient Lewis Acid Systems for the A3 Coupling reaction
Cimarelli C., a Navazio F.,a Rossi F. V.a, Del Bello F., Marcantoni E.a
aSchool of Science and Technology, Chemistry Division, University of Camerino, Via S. Agostino 1, 62032 Camerino; e-mail: [email protected]
Propargylamines are an attractive class of molecules because of their particular molecular skeleton, that contains an amine group located in β-position to an alkyne moiety suitable for many chemical transformations. In recent years they received a growing interest as key intermediates for several biologically active compound, natural products and also different heterocycles.[1,2]
Our goal was the development of green and simple methodologies for the synthesis of secondary propargylamines by Lewis acid catalyzed or promoted A3 reaction among aldehydes, alkynes and primary amines, that are in general less applied in such reactions because of their lower reactivity. In particular, we studied two different pathway: the CuSO4/NaI system in one pot fashion and the CeCl3/CuI system in one pot/two steps way (Scheme 1).
Scheme 1. CeCl3·7H2O/CuI and CuSO4/NaI catalyzed A3 reaction.
Heptahydrated CeCl3 is reported to be an excellent catalyst for many useful organic transformation as the synthesis of imines. Its efficacy as Lewis acid is enhanced in the presence of inorganic iodides/iodide salt and being cooper the transition metal of choice for A3 reactions, CuI was used.[3]
Also the CuSO4/NaI couple has revealed to be an interesting Lewis acid system as an alternative to CeCl3/CuI system which allow the formation of CuI in situ by quantitative spontaneous reaction that takes place in few seconds.[4]
Typically CuSO4/NaI catalysed reactions are faster than CeCl3·7H2O/CuI reactions, but suffer of some disadvantages, such as lower yields, and a narrower applicability. Both reaction conditions have been applied to different aldehydes (aromatic and aliphatic) and to chiral starting materials, the amine in general has no effect on the reaction outcome.
The relevant Glaser coupling drawback observed in the CuSO4/NaI system conditions has been suppressed by adding some benzoic acid, and has not been observed with the CeCl3/CuI system.
References:
1) Lauder, K.; Toscani, A.; Scalacci, N.; Castagnolo, D. Chem. Rev. 2017, 117, 14091.
2) Peshkov, V. A.; Pereshivko, O. P.; Van der Eycken, E. V. Chem. Soc. Rev. 2012, 41, 3790.
3) G. Bartoli, E. Marcantoni, M. Marcolini, L. Sambri, Chem. Rev. 2010, 110, 6104.
4) Bailey, A. D.; Cherney, S. M.; Anzalone, P. W.; Anderson, E. D.; Ernat, J. J.; Mohan, R. S. Synlett 2006, 215
Tephra architecture, pyroclast texture and magma rheology of mafic, ash-dominated eruptions: the Violent Strombolian phase of the Pleistocene Croscat (NE Spain) eruption.
No full textDeep explosive focal depths during maar forming magmatichydrothermal eruption: Baccano Crater, Central Italy
No full textAbstract We describe the eruptive activity of the
Pleistocene composite Baccano maar crater in the
Sabatini Volcanic Complex (Central Italy) combining
stratigraphy, grain size/componentry and rare earth
element and Yttrium (REY) composition of its eruptive
products with the stratigraphy and geothermal data
derived from deep wells drilled on the Baccano structural
high. The main lithological characteristics of the basal
Baccano maar pyroclastic deposit, composed of more
than 60% wt of non-thermometamorphosed lithic clasts
from the sedimentary basement, show that the first
eruption was magmatic-hydrothermal in nature. The
lithology of the sedimentary lithic clasts indicates that
the fragmentation level was at a depth of −1,000 to −1,200 m,
with fragment depth verified by deep well stratigraphy. The
15% wt juvenile non-vesicular glass components suggest that
magma played a minor role in powering the eruption.
Assuming that the high-salinity hot hydrothermal fluids
(365<T<410°C and P∼25 MPa), hosted in the highly
permeable and confined aquifer below the Baccano maar
are representative of those at the time of the eruption, we
propose that hydrofracturing would have triggered the
eruption caused by overpressure at the top of the geothermal
aquifer. REY analysis performed on pyroclastic fragments
and basement rocks suggest that partial dissolution of the
deeper limestones (>−1,400 m) by the aggressive hydrothermal
fluids enriched in acid components (HF, HCl, and
H2SO4) may have contributed to increased CO2 partial
pressure that helped to drive the hydrofracturing. This could
have caused rapid vapour separation and pressure drop,
allowing the almost simultaneous breaking of the aquifer
cover and brecciation of the calcareous units down to −1,000
to −1,200 m depth. The relative abundance of calcareous
lithics in the basal part of the first Baccano eruptive unit,
representing about the upper 200 m of stratigraphy below the
top of the Baccano structural high, reveals the descent of the
piezometric surface during the eruption. Combining deep
well information and maar product stratigraphy, using also
REY data from maar pyroclastic fragments and the basement
rocks we draw an interpretative model for the Baccano maarforming
eruption, concluding that a) magmatic-hydrothermal
eruptions may originate deeper than previously thought,
and b) hydrothermal fluids circulating in limestone
aquifers m
CeCl3·7H2O/NaI as Lewis acid catalyst in the Povarov reaction for the synthesis of functionalized tetrahydroquinolines
No full textMany different biologically active compounds contain the widespread scaffold of tetrahydroquinolines. Hence the interest toward their synthesis has stimulated the development of several synthetic strategies, among which the Povarov reaction is one of the most applied. The performance of this three-components imino Diels-Alder reaction can be improved by Lewis acid catalysis. In the last years the search for more economic and environmentally benign synthetic methodologies has stimulated the use of nontoxic and nonexpensive catalytic systems, and in this perspective Cerium trichloride has became interesting because of its low toxicity and cost and for the ease of application also in non anhydrous conditions.2,3
Here we describe the study of the CeCl3·7H2O/NaI system as Lewis acid catalyst in the Povarov reaction for the synthesis of substituted tetrahydroquinolines.
The reaction proceeds well, in acceptable reaction times and up to 86% yield. Both syn and anti diastereomers of the final tetrahydroquinoline can be obtained preferentially, depending on the reaction conditions, because the stereoselectivity is opposite in acetonitrile or in solventless conditions. Also substituted anilines and aromatic aldehydes have been employed with good results. A further investigation was made about the mechanism, to understand the formation of the main byproducts
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