Silver Triflate/p-TSA Co-Catalysed Synthesis of 3-Substituted Isocoumarins from 2-Alkynylbenzoates

In this paper, we describe the silver triflate/p-toluensulfonic acid co-catalysed synthesis of seventeen isocoumarins and two thieno[2,3-c]pyran-7-ones starting from 2-alkynylbenzoates and 3-alkynylthiophene-2-carboxylates, respectively. The reactions proceed with absolute regioselectivity under mild reaction conditions and low catalyst loading, to give the desired products in good to excellent yields. A conceivable reaction mechanism is proposed and supported by isotope-exchange tests, and 1H NMR studies and ad-hoc experiments

Domino Addition/Cycloisomerization Reactions of 2-Alkynyl-Arylaldehydes: Silver Catalyzed Synthesis of 1,3-Dicarbo-Substituted Isochromenes

One of the most efficient methods for the construction of 1-substituted isochromenes (and related heteroaryl compounds) is the metal catalyzed regioselective domino cycloisomerization/nucleophilic addition reaction of a 2-alkynyl(hetero)arylaldehyde in the presence of a suitable nucleophile.(1) The reaction with oxygen nucleophiles is the probably the most studied one. Several metal catalyst have been used, and our group recently gave a contribution in the field of silver catalyzed(2) synthesis of 1-alkoxyisochromenes.(3) Conversely, the reaction with carbon nucleophiles, and in particular with enolizable carbonyl compounds, is relatively less investigated.(4) We report here our recent results regarding the silver catalyzed synthesis of 1,3-dicarbo-substituted isochromene derivatives starting from 2-alkynyl(hetero)arylaldehydes and enolizable carbonyl compounds.(5) The reaction proceeded in a cascade fashion under mild reaction conditions with absolute regioselectivity and moderate-to-good yields. In some cases, the reaction produced unexpected diastereoisomeric couple of homodimeric products. The divergent formation of the 1-carbosubstituted isochromenes and the alternative homodimeric products has been tentatively explained by some experiments and two conceivable competitive paths have been proposed

The neglected brother: silver catalyzed domino reactions involving alkynes

Among the noble metals used in homogeneous catalysis, silver is the most neglected one, and only with the new millennium it has been rediscovered as suitable catalyst for a number of different organic transformations including the synthesis of heterocycles. Beside the versatility of copper catalysts and the much-in-vogue gold catalysis, silver salts and complexes demonstrated to be able to promote a number of reactions involving both sigma- and pi- activation. Its ability to act as Lewis acid as well as transition metal can be profitably used to promote domino and multicomponent transformations involving multiple bonds and heteroatoms. A certain number of examples in which silver catalysts effectively replaced copper ones or displayed an activity comparable \u2013 or higher \u2013 than more expensive gold catalysts have been reported. Here, our recent findings on silver catalyzed domino and multicomponent reactions involving alkynes will be disclosed. In particular, this talk will be focused both on domino addition/annulation reactions of 2-alkynylacetophenone derivatives with ammonia by means of simple silver salts catalysts and on the activity of some original pyridine-containing tetra-aza macrocyclic silver complexes, called [Ag(I)(Pc-L)]), in two different transformations: the regioselective domino addition/cycloisomerization reaction of 2-alkynylbenzaldehydes with alcohols and the A3-coupling multicomponent reaction

Catalytic transformations of indoles: recent achievements and new perspectives for the synthesis of complex indole derivatives

Transformation of simple indoles into (polycyclic) complex scaffolds has become the object of intensive studies in synthetic organic chemistry due to ubiquitous occurrence of indole core in the structure of relevant molecules In particular, catalytic-promoted manipulation of indoles have become an incomparable tool to increase indole structural complexity working under exceedingly mild conditions and in a regio- and stereo-controlled fashion. In this context we reported in the last years the synthesis of complex carbazole derivatives through gold-catalyzed (4+2) cycloaddition reactions of vinylindoles with different \u3c0-systems and the functionalization of structurally simple indoles with challenging metal-activated electrophiles. Taking into account these premises, this oral communication will deal with our recent achievements in the field of cycloaddition reactions involving vinylindoles as 4\u3c0 systems and in gold-catalyzed cascade reactions on indole-based scaffolds. In particular we were able to extend cycloaddition of vinylindoles besides (4+2) processes to synthetize cyclohepta[b]indoles. Moreover, we explored the reactivity of 4H-furo[3,2-b]indoles with gold-activated \u3c0-systems to synthetize 2-spiro-3-oxindoles and 2-alkenyliden-indolin-3-ones selectively. Advantages of our methods as well as limitations and future perspectives will be discussed

A state-space partitioned time integration algorithm for real-time hybrid simulation with nonlinear numerical subdomains

This paper describes a state-space partitioned algorithm for real-time hybrid simulation. The state-space modeling is proposed to represent nonlinear numerical substructures. The effectiveness of the proposed method is demonstrated for a virtual bridge case study equipped with seismic isolation devices

Gold-catalyzed cascade reactions of 4H‐furo[3,2‐b]indoles with allenamides: synthesis of indolin-3-one derivatives

2-Spirocyclopentane-1,2-dihydro-3H-indol-3-ones (namely, spiropseudo-indoxyls) constitute privileged scaffolds in organic synthesis and represent core components of different indole alkaloids (e.g. aristotelone and brevianamide A) and of molecules applied as functional dyes. In addition, they have found also an application as useful intermediate in the total synthesis of minfiensine. Taking into account these premises and our expertise in gold-catalyzed indole functionalization, we tested the reactivity of 4H-furo[3,2-b]indoles in the presence of electrophilic gold(I) activate \u3c0-systems (allenamides) with the aim to develop a new cascade process for the synthesis of these relevant scaffolds (Scheme 1). In this poster we present the obtained results together with the scope and limitation of the method and the proposed reaction mechanism

Performance-based Earthquake Evaluation of a Full-Scale Petrochemical Piping System

Assessment of seismic vulnerability of industrial petrochemical and oil & gas piping systems can be performed, beyond analytical tools, through experimental testing as well. Along this line, this paper describes an experimental test campaign carried out on a full-scale piping system in order to assess its seismic behaviour. In particular, a typical industrial piping system, containing several critical components, such as elbows, a bolted flange joint and a Tee joint, was tested under different levels of realistic earthquake loading. They corresponded to serviceability and ultimate limit states for support structures as suggested by modern performance-based earthquake engineering standards. The so called hybrid simulation techniques namely, pseudo-dynamic and real time testing with dynamic substructuring, were adopted to perform seismic tests. Experimental results displayed a favorable performance of the piping system and its components; they remained below their yielding, allowable stress and allowable strain limits without any leakage even at the Near Collapse limit state condition for the support structure. Moreover, the favourable comparison between experimental and numerical results, proved the validity of the proposed hybrid techniques alternative to shaking table tests

Mild AgOTf Catalyzed Synthesis of 1-Carbosubstituted-isochromenes

One of the most efficient methods for the construction of 1-substituted isochromenes (and related heteroaryl compounds such as pyrano[4,3-b]pyridines) is the metal catalyzed regioselective domino cycloisomerization/nucleophilic addition reaction of a properly substituted 2-alkynyl(hetero)arylaldehyde in the presence of a suitable nucleophile. The reaction with oxygen nucleophiles is the most studied and several metal catalyst, i.e., Pd(II), Cu(I), Ag(I), Au(I) and In(III), demonstrated to be effective for synthesis of 1-alkoxyisochromenes. Conversely, the reaction with carbon nucleophiles, and in particular with enolizable carbonyl compounds, is relatively less investigated. In connection with our ongoing interest in the development of silver catalysed domino approaches involving alkyne derivatives, we report here a silver catalyzed domino approach to isochromenes starting from 2-alkynyl(hetero)arylaldehydes and enolizable carbonyl compounds. The reaction yields range from fair to very good. The reaction mechanism is also investigated and the formation of by-products discussed

Gold-Catalyzed Cascade Reactions of 4H‑Furo[3,2‑b]indoles with Propargyl Esters: Synthesis of 2-Alkenylidene-3-oxoindolines

2-alkenyliden-indolin-3-ones were synthesised in high yields via a cascade reaction between 4H\u2011furo[3,2\u2011b]indoles and propargyl esters. The cascade sequence involves initial formation of a gold-carbene specie via cationic gold(I) catalysed 1,2-acyloxy migration of properly substituted propargyl esters followed by gold-carbene to furoindole addition and successive furan ring-opening affording the final products. The obtained compounds contain an extended \uf070-system linked at the C2 of the indolin-3-ones, they are characterised by intense colouration (from yellow to purple) and were characterised by UV mesearurements