Search

The Baeyer–Villiger oxidation of cyclic ketones (I) to the corresponding lactones (II) can be improved using m-CPBA under microwave dielectric heating. A dramatic reduction of time—3 min compared to 5 days at room temperature—was observed to transform cycloheptanone into oxocan-2-one. Ω-Hydroxyalkyl hydroxamic acids (III), key intermediates for a rapid access to potent histone deacetylase inhibitors, are obtained in one-pot reaction of lactones using the Weinreb amidation.

High level ab initio molecular orbital calculations which include correlation energy, zero-point energies, and thermal corrections have been used to explore the C2H&l+ hypersurface. The 1-chloroethyl cation is the global minimum with the chloronium ion lying 4.3 kcal mol-' above it at the MP4SDTQ/6-3 11G(2df,p)//MP2/6-3 1 lG(d,p) level. The energy barrier for the conversion of the chloronium ion to the 1-chloroethyl cation was calculated to be 27.8 kcal mol-' at the MP4 level and was found to be sensitive to electron correlation. The transition structure for interconversion of these two ions has been fully characterized with calculation of vibrational frequencies at MP2/6-31 lG(d,p). The 2-chloroethyl cation, which is a minimum with CI symmetry at the SCF/6-31G(d,p) level, collapses without a barrier to the 1 -chloroethyl cation when zero-point energies are included. High-energy isomers, chlorine-protonated vinyl chloride, and an ion-dipole complex have also been found on the C2H4C1+ surface. Vinyl chloride protonates on the carbon of the CHI group and has a proton affinity of 171.4 kcal mol-'. Calculated enthalpies of formation M0f,298 for the 1-chloroethyl cation and the chloronium ion are 198.1 and 202.0 kcal mol-', respectively. The difference (3.9 kcal mol-1) in AH0r,298 between these two isomers compares with experimentally determined differences of 5.6 and 2 kcal mol-'. Calculated vibrational frequencies and intensities are compared with the experimental spectra, and if only one ion contributes to these spectra, the calculations favor the chloronium ion.

Ab initio molecular orbital calculations are reported for methylenes CXY, methylidynes CX, and anions CXY - and CX - , where X and Y are all possible combinations of H, F, and Cl. Structures were optimized at SCF/6-311++G(d,p), and single point calculations are reported at both MP4SDTQ/6-31 1++G(2df,p) and, for the smaller molecules, at MP4SDTQ/6-311++G(3df,3pd). For anions containing chlorine, optimization at SCF/6-31++G(d,p) gave unrealistically long bond lengths, and more acceptable structures were achieved by inclusion of electron correlation at MP2/6-31++G(d,p)

Ab initio molecular orbital calculations have been performed on all possible neutral molecules and cations of the type CHmCln (m + n = 1−3). Equilibrium structures were optimized using gradient techniques at HF/6-31G(d,p), MP2/6-311G(d,p), QCISD/6-311G(d,p), and MP2/6-311++G(d,p). Thermochemical properties (standard enthalpies of formation, adiabatic ionization energies, and proton affinities) have been calculated at QCISD(T)/6-311++G(3df,3pd)//MP2/6-311++G(d,p) and QCISD(T)/6-311G(2df,p)//QCISD/6-311G(d,p), both including core-electron correlation, and at MP4SDTQ/6-311G(2df,p)//MP2/6-311G(d,p), frozen core. Calculations at the first level of theory are accurate to ±1.0 kcal mol-1, and at the second and third levels of theory, to ±2.3 kcal mol-1. Recent experimental data are critically reviewed against these calculated results, and theory indicates that some experimental values are incorrect. Calculated QCISD(T)/6-311++G(3df,3pd) values for the enthalpies of formation for CCl+ and CHCl+ are 304.9 and 286....

L -Glutamic acid was transformed into β-keto-phosphonate in two steps. This compound was employed in the stereocontrolled synthesis of cis-5-substituted prolines through a Woodward― Horner―Emmons (WHE) reaction with different aldehydes followed by hydrogenolysis/hydrogenation-mediated ring closure. We found also that a one-pot sequential hydroformylation―WHE reaction was possible with cis-5-substituted prolines. In addition to differently functionalised prolines, an indolizidine amino acid with a structure related to constrained peptidomimetics was obtained.

Furanyl and oxazolyl N-substituted imidazoline salts were prepared by reacting furanyl and oxazolyl esters with ethylenediamine and trimethyl aluminum, followed by the addition of methyl iodide or hydrogen chloride. The piperidinium salts were prepared by treating furanyl and oxazolyl chlorides with piperidine base, followed by the addition of methyl iodide or hydrogen chloride.