Valerio Bertolasi

Publications (54)156.81 Total impact

• Article: Unexpected reactivity of diaryl α-diketones with thiazolium carbenes: discovery of a novel multicomponent reaction for the facile synthesis of 1,4-thiazin-3-ones.

  Valerio Bertolasi, Olga Bortolini, Adelaide Donvito, Giancarlo Fantin, Marco Fogagnolo, Pier Paolo Giovannini, Alessandro Massi, Salvatore Pacifico
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  ABSTRACT: Diaryl α-diketones do not undergo polarity reversal in the presence of (benzo)thiazolium carbenes but are engaged in a novel multicomponent reaction with water to efficiently give medicinally relevant 1,4-thiazin-3-one heterocycles. Three different sets of conditions have been optimized to furnish the title compounds in fair to excellent yields depending on the electronic properties of α-diketone aromatic substituents and thiazolium or benzothiazolium substrate. A plausible reaction mechanism is also proposed based on the isolation and characterization of the postulated key intermediate and isotopic labeling experiments.
  Organic & Biomolecular Chemistry 07/2012; 10(32):6579-86. · 3.70 Impact Factor
• Article: Hydrogen Bonding and Electron Donor−Acceptor (EDA) Interactions Controlling the Crystal Packing of Picric Acid and Its Adducts with Nitrogen Bases. Their Rationalization in Terms of the pKa Equalization and Electron-Pair Saturation Concepts

  Valerio Bertolasi, Paola Gilli, Gastone Gilli
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  ABSTRACT: The structures of picric acid and 14 of its adducts with N-bases were determined by X-ray diffraction. All intermolecular contacts shorter than the sum of the van der Waals radii were retrieved, classified as 81 conventional X−H···:Y (X,Y = N,O) and 108 weaker C−H···:O H-bonds and as 49 C/N←:O π*←n or π*(k)←n and four C←:C π*←π electron donor−acceptor (EDA) interactions, and carefully scrutinized to single out the general rules (if any) the 242 contacts are conforming to. X···Y distances and related EHB energies of the 81 X−H···:Y bonds are found to correlate with ΔpKa = pKa(X−H)−pKa(Y−H+), validating the pKaequalization principle for which strong H-bonds occur only when ΔpKa tends to zero. Moreover, by redefining all X/C−H···:Y bonds as X/C−H←:Y σ*←n EDA interactions, all contacts become EDA interactions, leading to formulate the electron-pair saturation rule for which “all electron donors of a closed-shell molecule (nonbonding pairs of lone pairs or π-bonding pairs of multiple bonds) become engaged in EDA interactions with the electron acceptors (X−H, C−H, π*(k), or π*) present, as far as they are available; when the acceptors are insufficient, they are saturated in order of decreasing EDA interaction strength”. It is shown that this novel rule provides a particularly easy way to look at crystal packing.
  05/2011;
• Article: Synthesis and separation of the enantiomers of the neuropeptide S receptor antagonist (9R/S)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (SHA 68).

  Claudio Trapella, Michela Pela, Luisa Del Zoppo, Girolamo Calo, Valeria Camarda, Chiara Ruzza, Alberto Cavazzini, Valentina Costa, Valerio Bertolasi, Rainer K Reinscheid, Severo Salvadori, Remo Guerrini
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  ABSTRACT: This study reports the synthesis, chromatographic separation, and pharmacological evaluation of the two enantiomers of the neuropeptide S receptor (NPSR) antagonist (9R/S)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (SHA 68). The (9R)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (compound 10) and (9S)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (compound 10a) were synthesized and their purity assessed by chiral chromatography. The absolute configuration of the enantiomer 10 has been assigned from the crystal structure of the corresponding (S)-phenyl ethyl amine derivative 8. Calcium mobilization studies performed on cells expressing the recombinant NPSR demonstrated that compound 10 is the active enantiomer while the contribution of 10a to the NPSR antagonist properties of the racemic mixture is negligible.
  Journal of Medicinal Chemistry 04/2011; 54(8):2738-44. · 4.80 Impact Factor
• Article: Metallacrowns of Ni(II) with α-aminohydroxamic acids in aqueous solution: beyond a 12-MC-4, an unexpected (vacant?) 15-MC-5.

  Dimitri Bacco, Valerio Bertolasi, Francesco Dallavalle, Lorenzo Galliera, Nicola Marchetti, Luciano Marchiò, Maurizio Remelli, Matteo Tegoni
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  ABSTRACT: Growing attention has been devoted in the recent years to a class of metallamacrocycles known as metallacrowns (MCs). They are structural analogues of crown ethers where the methylene bridges have been substituted by coordinative bonds formed by a transition metal ion ("ring" metal) and a nitrogen atom. The cavity of the metallacrown can accommodate an additional metal ion ("core" metal) either identical or different from the ring metal, thus forming a homo- or hetero-metallic MC. The most studied ring metal ion is certainly Cu(2+) and the aminohydroxamic acids have proved to be very suitable ligands to form MCs. The behavioural analogies between Cu(2+) and Ni(2+) in forming complexes, along with recent literature data in the solid state, prompted us to investigate the possible MC formation between Ni(2+) and both (S)-α-alaninehydroxamic acid and (S)-valinehydroxamic acid, in aqueous solution. Two metallacrowns, a 12-MC-4 and an unexpected 15-MC-5 have been detected by potentiometry and confirmed by ESI-MS results. Their structures are discussed on the basis of potentiometric, calorimetric, spectroscopic data and DFT calculations. The existence of a vacant 15-MC-5 species in solution can be put forward for the first time, making the present metal/ligand systems very interesting for their potential applications in cation recognition and separation. Finally, the crystal structure of the binary complex K[NiL(2)H(-1)]·5/3 H(2)O of (S)-α-alaninehydroxamic acid (LH) is also reported.
  Dalton Transactions 02/2011; 40(11):2491-501. · 3.84 Impact Factor
• Article: Crystal Chemistry and Prototropic Tautomerism in 2-(1-Iminoalkyl)- phenols (or naphthols) and 2-Diazenyl-phenols (or naphthols)

  Valerio Bertolasi, Paola Gilli, Gastone Gilli
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  ABSTRACT: This review reports a systematic investigation, carried out on the Cambridge Crystallographic Database (CSD), on the structural features of iminoalkyl-phenols (or naphthols) as well as azo-phenols (or naphthols). All these compounds form N-H…O/O-H…N intramolecular hydrogen bonds assisted by resonance (RAHB) in tautomeric equilibrium which can be finely tuned by the substituents. Accordingly, they can present reversible proton transfer leading to interesting properties such as thermochromism and photochromism. The phenol derivatives 2-(1-aryliminoalkyl)phenols and 2- arylazophenols display the predominance of the O-H…N form. Furthermore, they display the following features: i) strongly electron-donating substituents in p-position on the N-phenyl group shorten the N…O contact distance but not enough to produce the O-H…N to O-H…N/N-H…O transition; ii) such a transition can be however induced by strongly electron-withdrawing substituents at the phenol ring which increase the phenol acidity; iii) very similar effects are determined by intermolecular hydrogen-bonded O-H…O contacts with the phenolic oxygen which, stabilizing the N-H…O bond produce the O-H…N to O-H…N/N-H…O transition and, sometimes, the complete proton transfer to the pure NH… O form. The naphthol derivatives (1-(1-aryliminoalkyl-2-naphthols and 1-arylazo-2-naphthols) display the most interesting situation of two roughly isoenergetic O-H…N/N-H…O tautomers which can be tuned by modifying the Nsubstituent, the effects of substitution at the N-phenyl moiety being by far the most extensively studied. The structures of variously aryl-substituted 1-(1-aryliminoalkyl)-2-naphthols, though collected only at room temperature, indicate that almost all of them are tautomeric equilibria, even if full information on proton populations and dynamic or static nature of the proton disorder are not available. Conversely, the structures of a series of aryl-substituted 1-arylazo-2-naphthols have been recently determined at variable temperature showing that strongly electron-attracting substituents stabilize the pure N-H…O form, while substituents with increasing electron-donating properties transform the system into a dynamic, or static, N-H…O → ↞ O-H…N tautomeric equilibrium in the solid with an ever increasing population of the O-H…N azoenol tautomer.
  Current Organic Chemistry 01/2009; 13(3):250-268. · 3.06 Impact Factor
• Article: Predicting hydrogen-bond strengths from acid-base molecular properties. The pK(a) slide rule: toward the solution of a long-lasting problem.

  Paola Gilli, Loretta Pretto, Valerio Bertolasi, Gastone Gilli
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  ABSTRACT: Unlike normal chemical bonds, hydrogen bonds (H-bonds) characteristically feature binding energies and contact distances that do not simply depend on the donor (D) and acceptor (:A) nature. Instead, their chemical context can lead to large variations even for a same donor-acceptor couple. As a striking example, the weak HO-H...OH(2) bond in neutral water changes, in acidic or basic medium, to the 6-fold stronger and 15% shorter [H(2)O...H...OH(2)](+) or [HO...H...OH](-) bonds. This surprising behavior, sometimes called the H-bond puzzle, practically prevents prediction of H-bond strengths from the properties of the interacting molecules. Explaining this puzzle has been the main research interest of our laboratory in the last 20 years. Our first contribution was the proposal of RAHB (resonance-assisted H-bond), a new type of strong H-bond where donor and acceptor are linked by a short pi-conjugated fragment. The RAHB discovery prompted new studies on strong H-bonds, finally leading to a general H-bond classification in six classes, called the six chemical leitmotifs, four of which include all known types of strong bonds. These studies attested to the covalent nature of the strong H-bond showing, by a formal valence-bond treatment, that weak H-bonds are basically electrostatic while stronger ones are mixtures of electrostatic and covalent contributions. The covalent component gradually increases as the difference of donor-acceptor proton affinities, DeltaPA, or acidic constants, DeltapK(a), approaches zero. At this limit, the strong and symmetrical D...H...A bonds formed can be viewed as true three-center-four-electron covalent bonds. These results emphasize the role PA/pK(a) equalization plays in strengthening the H-bond, a hypothesis often invoked in the past but never fully verified. In this Account, this hypothesis is reconsidered by using a new instrument, the pK(a) slide rule, a bar chart that reports in separate scales the pK(a)'s of the D-H proton donors and :A proton acceptors most frequently involved in D-H...:A bond formation. Allowing the two scales to shift so to bring selected donor and acceptor molecules into coincidence, the ruler permits graphical evaluation of DeltapK(a) and then empirical appreciation of the D-H...:A bond strength according to the pK(a) equalization principle. Reliability of pK(a) slide rule predictions has been verified by extensive comparison with two classical sources of H-bond strengths: (i) the gas-phase dissociation enthalpies of charged [X...H...X](-) and [X...H...X](+) bonds derived from the thermodynamic NIST Database and (ii) the geometries of more than 9500 H-bonds retrieved from the Cambridge Structural Database. The results attest that the pK(a) slide rule provides a reliable solution for the long-standing problem of H-bond-strength prediction and represents an efficient and practical tool for making such predictions directly accessible to all scientists.
  Accounts of Chemical Research 11/2008; 42(1):33-44. · 21.64 Impact Factor
• Article: Formation of L‐Threonic Acid from L‐Ascorbic Acid Oxidative Ring Opening and its Coordination to PtII: X‐ray Crystal Structures of [Pt(threonato‐O,O′)(PPh3)2] and [Pt(oxalato)(PPh3)2]

  Paola Bergamini, Elena Marchesi, Andrea Marchi, Valerio Bertolasi, Marco Fogagnolo, Alessandro Canella
  Berichte der deutschen chemischen Gesellschaft 05/2008; 2008(19):3056 - 3061. · 2.94 Impact Factor
• Article: New Water‐Soluble Rhenium Complexes with 1,3,5‐Triaza‐7‐phosphaadamantane (PTA) – X‐ray Crystal Structures of [ReNCl2(PTA)3], [ReO2Cl(PTA)3], [ReCl3­(PTA)2(PPh3)], and [Re2N2Cl3(Et2dtc)­(PTA)4]

  Andrea Marchi, Elena Marchesi, Lorenza Marvelli, Paola Bergamini, Valerio Bertolasi, Valeria Ferretti
  Berichte der deutschen chemischen Gesellschaft 04/2008; 2008(17):2670 - 2679. · 2.94 Impact Factor
• Article: Synthesis, characterization and reactivity of new complexes of titanium and zirconium containing a potential tridentate amidinato-cyclopentadienyl ligand.

  Valerio Bertolasi, Rita Boaretto, Michele R Chierotti, Roberto Gobetto, Silvana Sostero
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  ABSTRACT: Group 4 metal complexes [M(eta(5)-C(5)Me(4)SiMe(2)-eta(1)-N-2R)(NMe(2))(2)] (R = pyridine, pyrazine, pyrimidine, thiazole, M = Ti; R = pyridine, thiazole; M = Zr) containing the tetramethylcyclopentadienyl-dialkylsilyl bridged amidinato as pendant ligand, were synthesized and characterized by elemental analysis, solution (1)H, (13)C and (15)N NMR spectroscopy and experimental (13)C and (15)N CPMAS in the solid state. The crystal structures of [Ti(eta(5)-C(5)Me(4)SiMe(2)-eta(1)-N-2R)(NMe(2))(2)] (R = pyridine, pyrazine, pyrimidine, thiazole) were determined by single crystal X-ray diffraction studies. All compounds exhibit a distorted tetrahedral geometry, with the ansa-monocyclopentadienyl-amido ligands acting in a bidentate mode. The [M(eta(5)-C(5)Me(4)SiMe(2)-eta(1)-N-2R)(NMe(2))(2)] (R = pyridine, thiazole; M = Zr, Ti) complexes are ethylene polymerization catalysts in the presence of MAO and they are active precursors in regioselective catalytic hydroamination operating with an anti-Markovnikov mechanism.
  Dalton Transactions 12/2007; · 3.84 Impact Factor
• Article: Preparation and characterization of some keto-bile acid azines.

  Valerio Bertolasi, Olga Bortolini, Giancarlo Fantin, Marco Fogagnolo, Daniela Perrone
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  ABSTRACT: New acyclic dimers of ketocholanic acids with hydrazine were obtained. Crystal structure was determined for the 3,7-dihydroxy-12-ketocholanic acid azine. Some distinctive (1)H NMR signals are assigned for the entire set of azines.
  Steroids 11/2007; 72(11-12):756-64. · 2.83 Impact Factor
• Article: Synthesis and structure of some azo coupled cyclic beta-enaminones.

  Petr Simůnek, Lucie Lusková, Markéta Svobodová, Valerio Bertolasi, Antonín Lycka, Vladimír Machácek
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  ABSTRACT: The reaction of 3-phenylaminocyclopent-2-en-1-one with 4-methyl, 4-methoxy and 4-chlorobenzenediazonium tetrafluoroborates was used to prepare the azo coupling products 3a-c. It was found that these compounds are present in both CDCl(3) solution and solid phase practically exclusively as (E)-3-phenylamino-2-(4-subst.phenyldiazenyl)cyclopent-2-en-1-ones with N--H...N intramolecular hydrogen bond. The substitution of the phenyl residue of the diazonium salt has no effect on the position of the tautomeric equilibrium. On the other hand, the compounds 4a, b formed by the reaction of 3-phenylamino-1H-inden-1-one with 4-methylbenzene- or benzenediazonium tetrafluoroborates exist in CDCl(3) solution and in solid phase as hydrazone compounds. In the solution they occur as a mixture of three forms, out of which two were identified as E/Z isomers with different types of hydrogen bonds. Compound 5 formed by the reaction of 3-amino-5,5-dimethylcyclohex-2-en-1-one with 4-methoxybenzenediazonium tetrafluoroborate is converted into a stable hydrochloride 5.HCl on standing in CHCl(3) solution; this product exhibits a high degree of delocalization of the positive charge. Its structure was studied by means of X-ray.
  Magnetic Resonance in Chemistry 05/2007; 45(4):330-9. · 1.44 Impact Factor
• Article: Photochemistry of trans‐ and cis‐[RuCl2(dmso)4] in Aqueous and Nonaqueous Solutions

  Małgorzata Brindell, Grażyna Stochel, Valerio Bertolasi, Rita Boaretto, Silvana Sostero
  Berichte der deutschen chemischen Gesellschaft 04/2007; 2007(16):2353 - 2359. · 2.94 Impact Factor
• Article: Synthesis and structure of some azo coupled cyclic β‐enaminones

  Petr Šimůnek, Lucie Lusková, Markéta Svobodová, Valerio Bertolasi, Antonín Lyčka, Vladimír Macháček
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  ABSTRACT: The reaction of 3-phenylaminocyclopent-2-en-1-one with 4-methyl, 4-methoxy and 4-chlorobenzenediazonium tetrafluoroborates was used to prepare the azo coupling products 3a-c. It was found that these compounds are present in both CDCl3 solution and solid phase practically exclusively as (E)-3-phenylamino-2-(4-subst.phenyldiazenyl)cyclopent-2-en-1-ones with NH···N intramolecular hydrogen bond. The substitution of the phenyl residue of the diazonium salt has no effect on the position of the tautomeric equilibrium. On the other hand, the compounds 4a, b formed by the reaction of 3-phenylamino-1H-inden-1-one with 4-methylbenzene- or benzenediazonium tetrafluoroborates exist in CDCl3 solution and in solid phase as hydrazone compounds. In the solution they occur as a mixture of three forms, out of which two were identified as E/Z isomers with different types of hydrogen bonds. Compound 5 formed by the reaction of 3-amino-5,5-dimethylcyclohex-2-en-1-one with 4-methoxybenzenediazonium tetrafluoroborate is converted into a stable hydrochloride 5·HCl on standing in CHCl3 solution; this product exhibits a high degree of delocalization of the positive charge. Its structure was studied by means of X-ray. Copyright © 2007 John Wiley & Sons, Ltd.
  Magnetic Resonance in Chemistry 03/2007; 45(4):330 - 339. · 1.44 Impact Factor
• Article: Synthesis, solution thermodynamics, and X-ray study of CuII [12]metallacrown-4 with GABA hydroxamic acid: an unprecedented crystal structure of a [12]MC-4 with a gamma-aminohydroxamate.

  Matteo Tegoni, Luca Ferretti, Francesco Sansone, Maurizio Remelli, Valerio Bertolasi, Francesco Dallavalle
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  ABSTRACT: The solution equilibria of gamma-aminobutanehydroxamic acid (GABAha) with H+ and Cu2+ were investigated by potentiometry, titration calorimetry, spectrophotometry, NMR spectroscopy, and ESI-MS. The thermodynamic parameters of the CuII [12]metallacrown-4 obtained for GABAha were compared with those of the corresponding complexes of (S)-alpha-Alaha and beta-Alaha. The stability (-DeltaG0) sequence was beta-Alaha>alpha-Alaha>GABAha, whereas the order of formation enthalpies (-DeltaH0) was beta-Alaha>GABAha>alpha-Alaha. These data were interpreted on the basis of the dimensions of the chelate rings and the planarity of the metallamacrocycles. The CuII [12]metallacrown-4 ([12]MC-4) complex of GABAha was isolated and its crystal structure, which is the first reported for a [12]MC-4 of a gamma-aminohydroxamic acid, fully supports the structural features interpreted from the thermodynamic data.
  Chemistry 01/2007; 13(4):1300-8. · 5.93 Impact Factor
• Article: Interplay between steric and electronic factors in determining the strength of intramolecular N-H...O resonance-assisted hydrogen bonds in beta-enaminones.

  Valerio Bertolasi, Loretta Pretto, Valeria Ferretti, Paola Gilli, Gastone Gilli
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  ABSTRACT: The crystal structures of five beta-enaminones are reported: (2Z)-3-(benzylamino)-1,3-diphenyl-prop-2-en-1-one, (2Z)-3-(benzylamino)-3-(2-hydroxyphenyl)-1-phenyl-prop-2-en-1-one, (2Z)-3-(benzylamino)-3-(4-methoxyphenyl)-1-(3-nitrophenyl)-prop-2-en-1-one, 2-{1-[(4-methoxyphenyl)amino]ethylidene}cyclohexene-1,3-dione and 2-{1-[(3-methoxyphenyl)amino]ethylidene}cyclohexene-1,3-dione. The structures were analysed and compared with those of similar compounds in order to establish which factors determine the range (2.53-2.72 A) of N...O hydrogen-bond distances in intramolecularly hydrogen-bonded beta-enaminones. It has been shown that, beyond electronic resonance-assisted hydrogen-bond effects modulated by substituents, the necessary requirements to produce very short N-H...O hydrogen bonding are steric intramolecular repulsions, including the embedding of an enaminonic C-C or C-N bond in an aliphatic six-membered ring. By considering the structural features it is possible to expect the strength of N-H...O hydrogen bonds adopted by specific beta-enaminones.
  Acta Crystallographica Section B Structural Science 01/2007; 62(Pt 6):1112-20. · 2.29 Impact Factor
• Article: pi-Bond cooperativity and anticooperativity effects in resonance-assisted hydrogen bonds (RAHBs).

  Valerio Bertolasi, Loretta Pretto, Gastone Gilli, Paola Gilli
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  ABSTRACT: Bond cooperativity effects, which are typical of ;resonant' chains or rings of pi-conjugated hydrocarbons, can also occur in hydrogen-bonded systems in the form of sigma-bond and pi-bond cooperativity or anticooperativity. sigma-Bond cooperativity is associated with the long chains of O-H...O bonds in water and alcohols while sigma-bond anticooperativity occurs when the cooperative chain is interrupted by a local defect reversing the bond polarity. pi-Bond cooperativity is the driving force controlling resonance-assisted hydrogen bonds (RAHBs), while pi-bond anticooperativity has never been considered so far and is investigated here by studying couples of hydrogen-bonded beta-enolone and/or beta-enaminone six-membered rings fused through a common C=O or C-C bond. The effect is studied by X-ray crystal structure determination of five compounds [(2Z)-1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione enol (1), (2Z)-1-(2-hydroxy-5-chlorophenyl)-3-phenyl-1,3-propanedione enol (2), (2Z)-1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione enol (3), (2Z)-1-(2-hydroxy-4-methyl-5-chlorophenyl)-3-phenyl-1,3-propanedione enol (4) and dimethyl(2E)-3-hydroxy-2-{[(4-chlorophenyl)amino]carbonyl}pent-2-enedioate (5)] and by extensive analysis of related fragments found in the CSD (Cambridge Structural Database). It is shown that fusion through the C=O bond is always anticooperative and such to weaken the symmetric O-H...O...H-O and N-H...O...H-N bonds formed, but not the asymmetric O-H...O...H-N bond. Fusion through the C-C bond may produce either cooperative or anticooperative hydrogen bonds, the former being more stable than the latter and giving rise to a unique resonance-assisted ten-membered ring running all around the two fused six-membered rings, which can be considered a type of tautomerism never described before.
  Acta Crystallographica Section B Structural Science 11/2006; 62(Pt 5):850-63. · 2.29 Impact Factor
• Article: Synthesis and cytotoxic activity of substituted 2-phenyl-3-hydroxy-4(1H)-quinolinones-7-carboxylic acids and their phenacyl esters.

  Miroslav Soural, Jan Hlavác, Pavel Hradil, Iveta Frysová, Marián Hajdúch, Valerio Bertolasi, Michal Malon
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  ABSTRACT: The preparation of 3-hydroxy-2-phenyl-4(1H)-quinolinones substituted in position 7 with a carboxyl group is described. The synthesis is based on the reaction of 2-aminoterephthalic acid with substituted alpha-bromoacetophenones and subsequent cyclization of the resulting bisphenacylesters in polyphosphoric acid. The reaction affords a mixture of substituted 3-hydroxy-2-phenyl-4(1H)-quinolinones 7-carboxylic acids as well as their phenacylesters. All quinolinones prepared (acids and phenacylesters) were tested for cytotoxic activity in vitro against five cancer cell lines and the results and a tentative structure-activity relationship are reported.
  European Journal of Medicinal Chemistry 05/2006; 41(4):467-74. · 3.35 Impact Factor
• Article: Novel 5-(4-Substituted-phenyldiazenyl)-1,3,2λ4-oxazaborines and Their Rearrangement to 1,2,4,3λ4-Triazaborines

  Markéta Pešková, Petr Šimůnek, Valerio Bertolasi, Vladimír Macháček, Antonín Lyčka
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  ABSTRACT: The reaction of substituted benzenediazonium tetraphenylborates with the β-enaminones derived from pentane-2,4-dione, 1-phenylbutane-1,3-dione, and 1,4-diphenylbutane-1,3-dione with a primary or secondary (N-methyl, N-phenyl) amino group in CH2Cl2 gives 5-(substituted-phenyldiazenyl)-2,2-diphenyl-4,6-disubstituted-1,3,2λ4-oxazaborines or 5-(substituted-phenyldiazenyl)-2,2-diphenyl-3,4,6-trisubstituted-1,3,2λ4-oxazaborines, respectively. The reaction intermediate of these compounds has been identified, and a mechanism for the reaction has been suggested. Substituted 1,3,2λ4-oxazaborines gradually rearrange into 1,2,4,3λ4-triazaborines at temperatures above 100 °C.
  03/2006;
• Article: Some new routes for the preparation of 3-amino-2-phenyl-4(1H)-quinolinones from anthranilamides.

  Pavel Hradil, Martin Grepl, Jan Hlavác, Miroslav Soural, Michal Malon, Valerio Bertolasi
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  ABSTRACT: [reaction: see text] Several new routes for the preparation of 3-amino-2-phenyl-4-1(H)-quinolinone 7a are compared. The most efficient is based on the cyclization of phenacyl anthranilamide 2a in the presence of (poly)phosphoric acid. The mechanisms of the rearrangements involved are discussed on the basis of the structures of isolated heterocyclic intermediates. The best methodology for the preparation of the title compound 7a was verified, and 10 other quinolinones 7 were prepared.
  The Journal of Organic Chemistry 02/2006; 71(2):819-22. · 4.45 Impact Factor
• Article: Synthesis of Heterocyclic Ligands by Diheterocyclization at the Rhenium(I) Allenylidene [(triphos)(CO)2Re{CCCPh2}](OSO2CF3). 1. Reactivity with Dipolar N,N-Heterocycles

  Nicoletta Mantovani, Paola Bergamini, Andrea Marchi, Lorenza Marvelli, Roberto Rossi, Valerio Bertolasi, Valeria Ferretti, Isaac de los Rios, Maurizio Peruzzini
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  ABSTRACT: 1,2,3-Diheterocyclizations at the allenylidene ligand in the complex [(triphos)(CO)2Re{CCCPh2}]OTf (1; triphos = MeC(CH2PPh2)3, OTf = OSO2CF3) readily occur upon reacting 1 with N,N-heterocycles such as 1H-benzotriazole, 2-aminopyridine, and 2-aminothiazole. The reaction of 1 with 1H-benzotriazole leads to (4). Deprotonation of 4 with sodium methoxide in tetrahydrofuran at room temperature yields the alkynyl derivative (5) via ring opening of the triazaindenyl moiety in 4. Reaction of 1 with 2-aminopyridine or 2-aminothiazole in CH2Cl2 leads to the heterobicyclic compounds (6) and (8), respectively. Both complexes undergo regioselective deprotonation at the N−H heterocycle group by treatment with sodium methoxide in THF, giving the neutral species (7) and (9), respectively. The X-ray structures of the new organorhenium species 4 and 7−9 have been determined, which have confirmed that the addition of the NH bond of the N,N-heterocycle occurs always across the Cβ−Cγ double bond of the allenylidene chain.
  12/2005;