ChemInform Abstract: Conformational Analysis of Organic Carbonyl Compounds. Part 8. Conformational Properties of Aroyl Derivatives of Thiophene and Benzo(b)thiophene Studied by X-Ray Crystallography. NMR Lanthanoid-Induced Shifts Spectroscopy, and MO ab i

ChemInform ◽  
1988 ◽  
Vol 19 (14) ◽  
Author(s):  
R. BENASSI ◽  
U. FOLLI ◽  
D. IAROSSI ◽  
A. MUSATTI ◽  
M. NARDELLI ◽  
...  
Keyword(s):  
Conformational Analysis ◽  
Carbonyl Compounds ◽  
X Ray ◽  
X Ray Crystallography ◽  
Conformational Properties ◽  
Derivatives Of

The direct electrochemical synthesis of some metal derivatives of lapachol

1997 ◽  
Vol 75 (5) ◽  
pp. 499-506 ◽  
Author(s):  
E.H. De Oliveira ◽  
G.E.A. Medeiros ◽  
C. Peppe ◽  
Martyn A. Brown ◽  
Dennis G. Tuck
Keyword(s):  
Electrochemical Oxidation ◽  
Copper Atom ◽  
Electrochemical Synthesis ◽  
Acetonitrile Solution ◽  
Triclinic Space Group ◽  
X Ray ◽  
Metal Anode ◽  
X Ray Crystallography ◽  
Metal Derivatives ◽  
Derivatives Of

The electrochemical oxidation of a sacrificial metal anode (M = Zn, Cd, Cu) in an acetonitrile solution of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone, lapachol, C15H14O3 (=HL) gives ML2. The results are in keeping with earlier work on direct electrochemical synthesis in related systems. Adducts with 2,2′-bipyridine (bpy) and N,N,N′,N′-tetramethylethanediamine (tmen) have also been prepared. The structure of the 2,2′-bipyridine adduct of Cu(lapacholate)2 has been established by X-ray crystallography. The parameters are triclinic, space group [Formula: see text], a = 12.748(59) Å, b = 13.859(49) Å, c = 11.770(59) Å, α = 108.30(4)°, β = 108.08(3)°, γ = 68.94(3)°, Z = 2, R = 0.059 for 2256 unique reflections. The copper atom is in a distorted CuN2O2O2′ environment. The mechanism of the formation of this Cu(lapacholate)2 is discussed. Keywords: electrochemical synthesis, lapachol, X-ray crystallography, copper(II) complex.

Triazene derivatives of (1,x-)diazacycloalkanes. Part VI. 3-({5,5-Dimethyl-3-[2-aryl-1-diazenyl]-1-imidazolidinyl}methyl)-4,4-dimethyl-1-[2-aryl-1-diazenyl]imidazolidines — Synthesis, characterization, and X-ray crystal structure

2006 ◽  
Vol 84 (10) ◽  
pp. 1294-1300 ◽  
Author(s):  
Keith Vaughan ◽  
Shasta Lee Moser ◽  
Reid Tingley ◽  
M Brad Peori ◽  
Valerio Bertolasi
Keyword(s):  
Crystal Structure ◽  
Significant Degree ◽  
Ion Trapping ◽  
Published Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diazonium Ion ◽  
Derivatives Of ◽  
C Nmr

Reaction of a series of diazonium salts with a mixture of formaldehyde and 1,2-diamino-2-methylpropane affords the 3-({5,5-dimethyl-3-[2-aryl-1-diazenyl]-1-imidazolidinyl}methyl)-4,4-dimethyl-1-[2-aryl-1-diazenyl]imidazolidines (1a–1f) in excellent yield. The products have been characterized by IR and NMR spectroscopic analysis, elemental analysis, and X-ray crystallography. The X-ray crystal structure of the p-methoxycarbonyl derivative (1c) establishes without question the connectivity of these novel molecules, which can be described as linear bicyclic oligomers with two imidazolidinyl groups linked together by a one-carbon spacer. This is indeed a rare molecular building block. The molecular structure is corroborated by 1H and 13C NMR data, which correlates with the previously published data of compounds of types 5 and 6 derived from 1,3-propanediamine. The triazene moieties in the crystal of 1c display significant π conjugation, which gives the N—N bond a significant degree of double-bond character. This in turn causes restricted rotation around the N—N bond, which leads to considerable broadening of signals in both the 1H and 13C NMR spectra. The molecular ion of the p-cyanophenyl derivative (1b) was observed using electrospray mass spectrometry (ES + Na). The mechanism of formation of molecules of type 1 is proposed to involve diazonium ion trapping of the previously unreported bisimidazolidinyl methane (13).Key words: triazene, bistriazene, imidazolidine, synthesis, X-ray crystallography, NMR spectroscopy.

scholarly journals NMR and X-ray studies of apetalic acid isolated from Calophyllum brasiliense and of its chiral amides

2021 ◽  
Author(s):  
Marie-Rose Van Calsteren ◽  
Ricardo Reyes-Chilpa ◽  
Chistopher K Jankowski ◽  
Fleur Gagnon ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Antimycobacterial Activity ◽  
Side Chain ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Rain Forests ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calophyllum Brasiliense ◽  
Derivatives Of

The tropical tree Calophyllum brasiliense (Clusiaceae) grows in the rain forests from Brazil to Mexico. Its leaves, as well as those of other Calophyllum species, are rich sources of chromanone acids, such as apetalic acid, isoapetalic acid, and their derivatives. Apetalic acid has shown significant antimycobacterial activity. The biological activity of apetalic acid has been related to the configuration of three asymmetric centers and the stereochemistry of the molecule; however, the C-19 configuration in the acidic side chain has not been fully resolved. For this reason, the unequivocal determination of the absolute configuration by means of X-ray crystallography in a sample of unique homogeneous apetalic acid stereoisomer was the most important point to start this study. We prepared some chiral amides using the carboxyl group. We determined the C-19 stereochemistry of apetalic acid, and its specific chiral derivatives, using NMR, X-ray diffraction methods, and molecular mechanics. Finally, we observed that steric hindrance in the side chain of apetalic acid leads to restriction of rotation around the pivotal link C-10 and C-19 establishing chiral centers at C2(R), C3(S), and C19(R). We were able to separate derivatives of these two high-rotatory-barrier conformers of apetalic acid by forming diastereoisomeric amides with phenylglycine methyl ester having a chiral center at C-2’. Our results allowed the conclusion of the existence of atropisomerism in the apetalic acid molecule.

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