ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for resonance-assisted hydrogen bonding from crystal-structure correlations on the enol form of .beta.-diketone fragmentGastone Gilli, Fabrizio Bellucci, Valeria Ferretti, and Valerio BertolasiCite this: J. Am. Chem. Soc. 1989, 111, 3, 1023–1028Publication Date (Print):February 1, 1989Publication History Published online1 May 2002Published inissue 1 February...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for resonance-assisted hydrogen bonding. 4. Covalent nature of the strong homonuclear bond. Study O-H--O system by crystal structure correlation methodsPaola Gilli, Valerio Bertolasi, Valeria Ferretti, and Gastone GilliCite this: J. Am. Chem. Soc. 1994, 116, 3, 909–915Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February...

Unlike normal chemical bonds, hydrogen bonds (H-bonds) characteristically feature binding energies and contact distances that do not simply depend on the donor (D) acceptor (:A) nature. Instead, their context can lead to large variations even for a same donor−acceptor couple. As striking example, weak HO−H···OH2 bond in neutral water changes, acidic or basic medium, 6-fold stronger 15% shorter [H2O···H···OH2]+ [HO···H···OH]− bonds. This surprising behavior, sometimes called H-bond puzzle,...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvidence for resonance-assisted hydrogen bonding. 2. Intercorrelation between crystal structure and spectroscopic parameters in eight intramolecularly bonded 1,3-diaryl-1,3-propanedione enolsValerio Bertolasi, Paola Gilli, Valeria Ferretti, Gastone GilliCite this: J. Am. Chem. Soc. 1991, 113, 13, 4917–4925Publication Date (Print):June 1, 1991Publication History Published online1 May 2002Published inissue 1 June...

The resonance-assisted hydrogen bond (RAHB) is a model of synergistic interplay between π-delocalization and hydrogen-bond (H-bond) strengthening originally introduced (Gilli, G.; Bellucci, F.; Ferretti, V.; Bertolasi, V. J. Am. Chem. Soc. 1989, 111, 1023; Gilli, P.; G. 1991, 113, 4917) for explaining the abnormally strong intramolecular O−H···O bonds formed by ···OC−CC−OH··· β-enolone fragment I which are typical β-diketone enols. applicability this to N−H···O number heteroconjugated...

The tautomeric.O=C-C=N-NH triplebond --> <-- HO-C=C-N=N ketohydrazone-azoenol system may form strong N-H O/O-H N intramolecular resonance-assisted H-bonds (RAHBs) which are sometimes of the low-barrier H-bond type (LBHB) with dynamic exchange proton in solid state. problem competition these compounds is studied here through variable-temperature (100, 150, 200, and 295 K) crystal-structure determination pF = 1-(4-F-phenylazo)2-naphthol oF 1-(2-F-phenylazo)2-naphthol, two molecules that, on...

Beta-diketone enols are known to form intramolecular...O=C-C=C-OH... resonance-assisted hydrogen bonds (RAHBs) with O...O distances as short 2.39-2.44 A. However, even the most accurate diffraction studies have not been able assess certainty whether these very strong (H-bonds) be described proton-centered O...H...O in a single-well (SW) potential or dynamic static mixing of two O-H...O <= => O...H-O tautomers double-well (DW) one. This contribution reexamines problem and shows that methods...

Abstract The fact that hydrogen bonding is normally stronger than other nonbonding attractive forces can be exploited for the rational design of molecular crystals with known packing features and specific physical properties (crystal engineering). In present paper problem obtaining homodromous chains controlled by strong O–H ⃛ O interactions investigated, particular attention being paid to β‐ , is, infinite hydrogen‐bonded β‐diketone enol fragments OCCCOH ⃛, which are linked...

Phenyl-substituted 1-arylazo-2-naphthols (AAN) display ···HNNCCO··· ⇌ ···NNCCOH··· ketohydrazone−azoenol tautomerism and can form intramolecular resonance-assisted H-bonds from pure NH···O to N···HO through tautomeric dynamically disordered bonds according the electronic properties of their substituents. Three compounds this series (m-OCH3-AAN = mOM; p-Cl-AAN pCl; p-NMe2-AAN pNM2) have been studied by X-ray crystallography at four temperatures (100−295 K), showing that remarkably short...

A series of new phenoxy-thioether (OS) proligands have been synthesized. They were found to readily react with 1 equiv AlMe3 afford the corresponding Al chelate complexes {4,6-tBu2-OC6H2-2-CH2S(2-R-C6H4)}AlMe2 (R = H (1), Br (2), CH3 (3), CF3 (4)) in quantitative yields. All aluminum methyl are stable monomeric species. In solid state, as determined from X-ray crystallographic studies, complex 2 consists a four-coordinate species which metal center is chelated by sulfur and oxygen atoms...

A novel Au(III)–N-heterocyclic carbene organometallic complex supported by two N-heterocyclic (NHC) ligands was synthesized from Au(SMe2)Cl and 1-methyl-2-pyridin-2-yl-2H-imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate via a Ag intermediate. X-ray crystallography revealed the first example of square planar geometry adopted Au(III) species stabilized NHCs chloride ligands. The aforementioned Au(I)– Au(III)–NHC complexes were found to be more potent than cisplatin against HCT 116, HepG2,...

A novel and versatile strategy for the synthesis of heterocyclic α-amino acids has been described. The use components (aldehyde or β-ketoester) bearing a masked glycinyl moiety in Biginelli Hantzsch cyclocondensations allowed access to 4-dihydropyrimidinyl-α-glycines, 4-dihydropyrimidinyl-α-alanines, 4-pyridyl-α-alanines, 2-pyridyl-α-alanines classes. Dihydropyrimidinyl-amino were obtained as mixture diastereoisomers due formation stereocenter at C4 dihydropyrimidinone ring. Individual...

The aldehyde-ketoester-urea cyclocondensation reaction has been revisited using C-glycosylated reagents with the aim of exploring a potential entry to library dihydropyrimidinone glycoconjugates. A collection 13 mono- and bis-C-glycosylated dihydropyrimidinones prepared by parallel synthesis approach three-component promoter CuCl/AcOH/BF(3) x Et(2)O. sugar residues have installed at either N1, C4, or C6 in monoglycosylated derivatives both C4 bisglycosylated products. products were obtained...

The first example of an iridium biscyclometalated complex with a C∧N∧C 2,6-diphenylpyridine (dppy)-type ligand, [(4'-(4-bromophenyl)-2:2',6':2' '-terpyridine)Ir(2,6-diphenyl-4-(4-tolyl)pyridine)](NO3) (1), has been synthesized and characterized by various techniques such as X-ray crystallography, mass spectrometry, 1H 13C NMR, cyclic voltammetry, both steady-state time-resolved emission absorption studies. Preliminary density functional theory calculations have also conducted. 1 crystallizes...

The crystal structures of seven compounds forming intermolecular N--H..-O hydrogen bonds connected by 7r-conjugated systems are reported: (1) 2-methyl-Nphenylprop-2-enamide; (2) 2-methyl-N-benzylprop-2-enamide; (3) p-methoxyacetoacetanilide; (4) dibenzamide; (5) 3-methyl-4-(3'-methyl- l'-phenylpyrazol-5'-yl)- 1 phenyl-4-pyrazolin-5-one; (6) 3-anilino-2-chloro-l,4naphthoquinone; (7) 3-phenethyl-7-methyl-5H-pyrazolo[4,3-d]-l,2,3-triazin-4(3H)-one. 32 other related surveyed in order to...

Abstract A general method for the homologation of aldehydes to α‐amino (aminohomologation) has been developed, which employs nitrones as iminium derivatives aldehydes. Key operations include a) addition a thiazole metalated at C‐2 N ‐benzylnitrone derived from aldehyde, b) reductive dehydroxylation resultant thiazolyl ‐benzylhydroxylamine, and c) unmasking formyl group ring. The sequence was studied by employing various chiral polyalkoxy dialdoses. 2‐lithiothiazole these syn ‐selective,...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereochemistry of the R1(X:)C(sp2)-N(sp3)R2R3 fragment. Mapping cis-trans isomerization path by rotation around carbon-nitrogen bond from crystallographic structural dataGastone. Gilli, Valerio. Bertolasi, Fabrizio. Bellucci, and Valeria. FerrettiCite this: J. Am. Chem. Soc. 1986, 108, 9, 2420–2424Publication Date (Print):April 1, 1986Publication History Published online1 May 2002Published inissue 1 April...

The structures of picric acid and 14 its adducts with N-bases were determined by X-ray diffraction. All intermolecular contacts shorter than the sum van der Waals radii retrieved, classified as 81 conventional X−H···:Y (X,Y = N,O) 108 weaker C−H···:O H-bonds 49 C/N←:O π*←n or π*(k)←n four C←:C π*←π electron donor−acceptor (EDA) interactions, carefully scrutinized to single out general rules (if any) 242 are conforming to. X···Y distances related EHB energies bonds found correlate ΔpKa...

Co-crystals are crystalline complexes of two or more molecules bound together in crystal lattices through noncovalent interactions. The solubility and dissolution properties co-crystals can allow to increase the bioavailability poorly water-soluble active pharmaceutical ingredients (APIs). It is currently believed that co-crystallization strategy should not induce changes on pharmacological profile APIs, even if it yet clear whether a co-crystal would be defined as physical mixture new...

A new class of compounds that incorporated the structural motif 1-(3',4',5'-trimethoxtbenzoyl)-3-arylamino-5-amino-1,2,4-triazole molecular skeleton was synthesized and evaluated for their antiproliferative activity in vitro, interactions with tubulin, cell cycle effects. The most active agent, 3c, antitumor vivo. Structure-activity relationships were elucidated various substituents on phenyl ring anilino moiety at C-3 position 1,2,4-triazole ring. best results inhibition cancer growth...

The β-diketone enol (or enolone) HO-C=C-C=O fragment produced by enolization of β-diketones is known to form strong intramolecular O-H...O hydrogen bonds where the decrease O...O contact distance (up 2.40 A) correlated with increased π-delocalization O-C=C-C=O heteroconjugated system; phenomenon has been interpreted resonance-assisted hydrogen-bonding (RAHB) model [Gilli, Bellucci, Ferretti & Bertolasi (1989). J. Am. Chem. Soc. 111, 1023-1028; Bertolasi, Gilli, Gilli (1991). 113, 4917-1925]

The cluster [Ni6(H2L)2(HL1)2(N3)8]·2C2H5OH·2H2O [1·2C2H5OH·2H2O], featuring four fused defective cubanes, has been obtained via azido-bridge-driven dimerization of two phenolate-centered trinuclear Ni3 fragments.