Convergent synthesis of mosloflavone, negletein and baicalein from crysin

An expeditious synthesis of three polyoxygenated flavones: mosloflavone, negletein and baicalein, starting from crysin, an easily available flavone, by a bromination/methoxylation procedure is reported. The convergent synthesis exploits a base induced Wesley-Moser type rearrangement.     

An easy one-pot stereoselective synthesis of 4-substituted and 4,5-disubstituted oxazolidin-2-ones from N-Boc-2,3-aziridino alcohols

A novel and efficient one-pot stereoselective transformation of N-(t-butoxycarbonyl)-2,3-aziridino alcohols into 4-substituted and 4,5-disubstituted oxazolidin-2-ones has been developed; these functionalized products are amenable to other elaborations, some of which are described.     

Synthesis of chiral non-racemic intermediates and Arg-Gly-Asp mimetics by CaLB-catalyzed resolution

The reactivity of both the ester and amine functions present in β-amino esters was tested in order to obtain the synthesis of enantiopure αvβ3 and α5β1 integrin ligands. CaLB successfully catalyzed both the enantioselective transesterification and the N-acylation of racemic β-amino esters, allowing the isolation of intermediates for the preparation of Arg-Gly-Asp (RGD) mimetic compounds. In particular, a CaLB-catalyzed amidation reaction with unprotected p-aminobenzylamine reduced the number of synthetic steps, thus avoiding protection and deprotection of the intermediate compounds. Following this procedure, RGD mimetics were isolated with high yields and enantiomeric purities.     

Isomerization dynamics and thermodynamics of ionic argon clusters

The dynamics and thermodynamics of small Ar(n) (+) clusters, n=3, 6, and 9, are investigated using molecular dynamics (MD) and exchange Monte Carlo (MC) simulations. A diatomic-in-molecule Hamiltonian provides an accurate model for the electronic ground state potential energy surface. The microcanonical caloric curves calculated from MD and MC methods are shown to agree with each other, provided that the rigorous conservation of angular momentum is accounted for in the phase space density of the MC simulations. The previously proposed projective partition of the kinetic energy is used to assist MD simulations in interpreting the cluster dynamics in terms of inertial, internal, and external modes. The thermal behavior is correlated with the nature of the charged core in the cluster by computing a dedicated charge localization order parameter. We also perform systematic quenches to establish a connection with the various isomers. We find that the Ar(3) (+) cluster is very stable in its linear ground state geometry up to about 300 K, and then isomerizes to a T-shaped isomer in which a quasineutral atom lies around a charged dimer. In Ar(6) (+) and Ar(9) (+), the covalent trimer core is solvated by neutral atoms, and the weakly bound solvent shell melts at much lower energies, occasionally leading to a tetramer or pentamer core with weakly charged extremities. At high energies the core itself becomes metastable and the cluster transforms into Ar(2) (+) solvated by a fluid of neutral argon atoms.     

Condensed 2-pyrrolidinone-1,2-oxazines from lithium enolate of 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid and β-aryl, β-nitroenamines

The reaction of the lithium enolate of 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid 3 with a series of β-aryl, β-nitroenamines unexpectedly afforded 6-aryl-2-benzyl-4-oxa-1-oxo-3a-methoxycarbonyl-2,5-diazaindenes 9a-d, whose structure was determined by analytical and NMR spectroscopical analysis. The structure of 9b was further confirmed by X-ray analysis. A reasonable mechanism for their formation is given.     

Highly regio- and stereoselective palladium-catalyzed allylic carbonate amination. A practical route to dehydro-β-amino esters

A pratical, highly enantioselective method for the synthesis of dehydro-β-amino acids was developed starting from easily accessible enantiopure allylic carbonates. The substitution with amines for C–N bond formation on these substrates bearing substituents on the Cα, Cβ, and Cγ position of the allylic system has received, until now, little attention. The reactions, carried out under palladium-catalyzed conditions, resulted in good yields and complete regioselectivity. Moreover, starting from enantiopure carbonates, complete retention of the configuration could be observed, affording enantiopure allylic amines.     

Chemistry at surfaces: from ab initio structures to quantum dynamics

Recent years have witnessed an ever growing interest in theoretically studying chemical processes at surfaces. Apart from the interest in catalysis, electrochemistry, hydrogen economy, green chemistry, atmospheric and interstellar chemistry, theoretical understanding of the molecule–surface chemical bonding and of the microscopic dynamics of adsorption and reaction of adsorbates are of fundamental importance for modeling known processes, understanding new experimental data, predicting new phenomena, controlling reaction pathways. In this work, we review the efforts we have made in the last few years in this exciting field. We first consider the energetics and the structural properties of some adsorbates on metal surfaces, as deduced by converged, first-principles, plane-wave calculations within the slab-supercell approach. These studies comprise water adsorption on Ru(0001), a subject of very intense debate in the past few years, and oxygen adsorption on aluminum, the prototypical example of metal passivation. Next, we address dynamical processes at surfaces with classical and quantum methods. Here the main interest is in hydrogen dynamics on metallic and semi-metallic surfaces, because of its importance for hydrogen storage and interstellar chemistry. Hydrogen sticking is studied with classical and quasi-classical means, with particular emphasis on the relaxation of hot–atoms following dissociative chemisorption. Hot atoms dynamics on metal surfaces is investigated in the reverse, hydrogen recombination process and compared to Eley–Rideal dynamics. Finally, Eley–Rideal, collision-induced desorption, and adsorbate-induced trapping are studied quantum mechanically on a graphite surface, and unexpected quantum effects are observed.