Synthesis of two new thioesters bearing ferrocene: Vibrational characterization and ab initio calculations. X-ray crystal structure of S-(2-methoxyphenyl)ferrocenecarbothioate

Structural and conformational properties of S-benzyl ferrocenecarbothioate (I) and S-(2-methoxyphenyl) ferrocenecarbothioate (II) are analyzed using data obtained from X-ray diffraction, vibrational data and theoretical calculations. According to chemical quantum calculations, the synperiplanar and antiperiplanar forms are found as the first and second more stable conformations, respectively, for the title compounds. The geometric parameters and normal modes of vibration were calculated using a density functional theory method (B3LYP) and the 6-31+G∗∗ basis set for all atoms except for iron. For this atom the calculations were carried out with the Lanl2dz basis set. The calculated parameters are in good agreement with the corresponding X-ray diffraction values. The combined experimental and theoretical approach allows a consistent assignment for most of the fundamental modes.     

Synthesis and structural characterization of metallated bioconjugates: C-terminal labeling of amino acids with aminoferrocene

Aminoferrocene, H₂N-Fc, has been substituted to the C-terminus of six amino acids using the HBTU/HOBt coupling protocol. The synthesized bioconjugates Boc-Aaa-NH-Fc, Aaa = Gly (1), Leu (2), Phe (3), Val (4), Cys(Acm) (5), Tyr(^tBu) (6) (Acm = acetamidomethyl, ^tBu = tert-butyl), have been characterized by ¹H NMR, ¹³C NMR, EI-MS, EI-HRMS, UV and CD spectroscopies. In addition, a VT NMR study on 4 and the X-ray structure of 1 are presented.     

Spectroscopic, structural, and conformational properties of (Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one, C12H12F3NO3: a trifluoromethyl-substituted β-aminoenone

The (Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one (C(12)H(12)F(3)NO(3)) compound was thoroughly studied by IR, Raman, UV-visible, and (13)C and (19)F NMR spectroscopies. The solid-state molecular structure was determined by X-ray diffraction methods. It crystallizes in the P2(1)/c space group with a = 12.1420(4) ?, b = 7.8210(3) ?, c = 13.8970(5) ?, β = 116.162(2)°, and Z = 4 molecules per unit cell. The molecule shows a nearly planar molecular skeleton, favored by intramolecular OH···O and NH···O bonds, which are arranged in the lattice as an OH···O bonded polymer coiled around crystallographic 2-fold screw-axes. The three postulated tautomers were evaluated using quantum chemical calculations. The lowest energy tautomer (I) calculated with density functional theory methods agrees with the observed crystal structure. The structural and conformational properties are discussed considering the effect of the intra- and intermolecular hydrogen bond interactions.     

Preyssler catalyst-promoted rapid,clean, and efficient condensation reactions for 3H-1,5-benzodiazepine synthesis in solvent-free conditions

A simple, convenient, and environmentally benign synthesis of 1,5-benzodiazepines is developed by condensing different o-phenylenediamines and 1,3-aryl-1,3-propanodiones. The reaction is catalyzed by a Preyssler (NaH₁₄P₅W₃₀O₁₁₀, HPA) heteropolyacid as a safe, clean, and recyclable catalyst. The method is operationally simple and provides access to a variety of 1,5-benzodiazepines in good to excellent yields.     

Hydrogen Bonds, Tautomers, and Conformation in 2-Hydroxyphenyl 2-hydroxy-2-(β-naphthyl)vinyl Ketone

Single crystal X-ray diffraction and IR spectroscopy have been used to study the conformation of 2-hydroxyphenyl 2-hydroxy-2-(-naphthyl)vinyl ketone in solid state. It was found that one of the two possible enol tautomeric forms is stabilized in the crystal. The 1-hydroxy-3-oxo-1,3-propenylene moiety, O=C—CH=C—OH, shows a strong intramolecular H bond with a definite character of reasonance-assisted hydrogen bond in spite of being in competition with ring intermolecular hydrogen bonds. The comparison of the present results with solution NMR data indicates that the molecular geometry in solid state and in solution are similar.     

One-pot synthesis of ferrocenyl-pyrimidones using a recyclable molibdosilicic H4SiMo12O40 heteropolyacid

A series of ferrocene-containing dihydropyrimidines (DHPs) were prepared by the one-pot Biginelli reaction of formylferrocene, 1,3-dicarbonyl component and urea/thiourea. The reaction was catalyzed by a commercial Keggin heteropolyacid (H₄SiMo₁₂O₄₀) as a safe, clean and recyclable catalyst. Three different synthetic protocols were examined in order to improve the yields of the reaction and to elucidate its mechanism. Intermediates of the competitive Knoevenagel reaction were also isolated. The methodology is operationally simple and provides access to highly substituted dihydropyrimidines containing ferrocene in very good yields. The catalyst can be used and recycled without appreciable loss of the catalytic activity.

     

One-pot synthesis of 2-trifluoromethylchromones

We report a simple and suitable method for the preparation of useful 2-trifluoromethylchromones in one step, in high yields and avoiding the use of solvents. We were able to detect the intermediate of this reaction. Furthermore a mechanism for the formation of the 7-methoxy-3-trifluoroacetyl-2-trifluoromethylchromone through the unexpected double trifluoroacetylation of 4-methoxy-2-hydroxyacetophenone followed by dehydration is also proposed. All compounds are fully identified and characterized by spectroscopic techniques.     

Simple and ecofriendly synthesis of dihydropyrimidinones (thiones), dihydropyridines,and pyridines using 3‐formylchromones as substrates assisted by a recyclable Preyssler heteropolyacid

Several dihydropyrimidinones/thiones, 1,4‐dihydropyridines, and pyridine derivatives were prepared in very good yields and purity values. The corresponding reactions were carried out by employing a bulk Preyssler heteropolyacid H₁₄[NaP₅W₂₉MoO₁₁₀] as an efficient and recyclable catalyst. The preparation of pyridine derivatives was carried out not through a usual procedure, i.e., the opening of the γ‐pyrone ring of 3‐formylchromone. In general, reactions took place in solvent‐free conditions at 80°C during short reaction times.     

Molecular structure,experimental and theoretical 1H and 13C NMR chemical shift assignment of cyclic and acyclic α,β‐unsaturated esters

The experimental ¹H and ¹³C NMR spectra of 13 phenyl cinnamates and four 4‐methylcoumarins were investigated and their chemical shifts assigned on the basis of the two‐dimensional spectra. For the unsubstituted cinnamic acid phenyl ester, optimized molecular structures were calculated at a B3LYP/6‐311++G(d,p) level of theory. ¹H and ¹³C NMR chemical shifts were also calculated with the GIAO method at the B3LYP/6‐311 + G(2d,p) level of theory. The comparison between experimental and calculated NMR chemical shift suggests that the experimental spectra are formed from the superposition spectra of the two lowest energy conformers of the compound in solution. The most stable s‐cis configuration found in our studies is also the conformation adopted for a related phenyl cinnamate in solid state. The experimental results were analyzed in terms of the substituent effects. Copyright © 2013 John Wiley & Sons, Ltd.