Preparative isolation of (+)-beta-eudesmol fromAmyris balsamifera

Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum distillation of the total oil. Step two was a medium pressure LC separation with an AgNO₃ impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related sesquiterpene alcohols (75% of the oil).     

DFT study and vibrational spectra of the phoshorus-containing G0 generation dendrimer

The Raman (10–3500 cm⁻¹) and infrared (150–3500 cm⁻¹) spectra have been recorded for tris(4-oxibenzaldehyde)thiophosphate. This compound includes structural parts of elementoorganic dendrimers: a core and terminal aldehyde groups. The structural optimization and normal mode analysis are performed for elementoorganic dendrimer on the basis of the ab initio density functional theory. It is found that the dendrimer exist in a single stable conformation with planar C₆H₄CHO fragments. Our calculations show that conformer with one trans and two gauche 4-oxibenzaldehyde groups is realized. All these observations suggest that steric congestion does not disturb the construction of dendrimers even for the highest generations, and that terminal groups are readily available for further reactions. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the studied dendrimers.     

Investigation of the mechanism of reaction of S-ethyl-N,N′-tetraethyldiamidothio-phosphite with [C5H 5Mn(CO)2NO]+BF by fourier transform infrared spectroscopy

FT-IR spectroscopy and a special mathematical program were used for the real-time monitoring of the mechanistic path of the reaction of S-ethyl-N,N-tetraethyldiamidothiophosphite with [CpMn(CO)-₂NO]⁺BFequation/tex2gif-stack-3.gif. The formation of a few intermediates is described.     

IR and NMR spectra,intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution

It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10–20 cm^?1) red shift of the IR bands of the NH₂ stretching vibrations, which suggests rather weak NH?N hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.     

FTIR and FT-Raman spectra and DFT vibrational analysis of phosphorus-containing dendrons

FTIR and FT-Raman spectra of four generations of phosphorus-containing dendrons with terminal aldehyde or PCl groups have been recorded and analyzed. Their spectral patterns are determined by the ratio T/R (T, the number of terminal groups; R, the number of repeated units). Bands assigned to the core, repeated units and terminal groups were separated by the difference spectroscopy method. The optimized geometry, frequencies and intensity of IR bands of G(1v) generation dendron with terminal aldehyde groups were obtained by the density functional theory (DFT). It was found that the internal skeleton of molecules exists in a single stable conformation with planar O-C(6)H(4)-CHN-N(CH(3))-P(S) fragments, but terminal groups may adopt the t,g,g- and t,-g,g-rotational isomers. The t,-g,g-conformer is 0.74 kcal/mol less stable compared to the t,g,g-conformer. The bond length and bond angles obtained by DFT show the best agreement with experimental data. Relying on DFT calculations a complete assignment of vibrations is proposed for different parts of the studied dendrons. The calculated frequencies and intensity of IR bands of the t,g,g- and t,-g,g-conformers of G(1v) are found to be in reasonable agreement with the experimental results. The most reactive site in dendron is the core function and vinyl group is preferred for nucleophilic attack. In dendrimer the most reactive are the terminal groups.     

A cobalt(ii) acetate complex with 1-(3,5-di-tert-butyl-4-hydroxybenzyl)-1H-indole-2,3-dione 3-thiosemicarbazone: synthesis and structure

A complex of Co^II with 1-(3,5-di-tert-butyl-4-hydroxybenzyl)-1H-indole-2,3-dione 3-thiosemicarbazone was obtained and identified by X-ray diffraction, IR and Raman spectroscopy, and quantum chemical calculations. The characteristic C=S frequencies in the IR spectra of the thiosemicarbazones were refined. The data obtained from different methods were compared, which allows more accurate spectroscopic studies of related structures.