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diastereoselective syntheses, enantioselective syntheses diastereoselective syntheses, enantioselective syntheses (incl. cis/trans-isomerism) O 0031 -034Synthetic Methodology for the Construction of Structurally Diverse Cyclopropanes.-Practical and efficient routes for the stereoselective conversion of homoallylic alcohols like (I) and (VII) to diastereomerically pure cis-and trans-1,2-disubstituted, and 1,2,3-trisubstituted cyclopropanes are developed. One route involves ring closing metathesis reaction of bisolefins like (III) to give after cleavage of the 7-membered ring the silylated cyclization precursors like (V). The other more efficient approach provides the cyclopropanes in just two steps by cross-metathesis reaction of the homoallylic alcohol and by activation of the cyclization precursors like (XV) with inexpensive SOCl 2 at room temperature. The cyclopropane product chirality is ultimatively controlled by the choice of homoallylic alcohol starting material.

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N-heterocyclic olefins (NHOs), IPrCH2 (1) and SIPrCH2 (2) (IPrCH2 = {N(2,6-iPr2C6H3)CH}2CCH2 and SIPrCH2 = {N(2,6-iPr2C6H3)CH2}2CCH2), react with HSiCl3 and afford IPrCH(SiHCl2) (3) and SIPrCH(SiHCl2) (4), respectively. Compounds 3 and 4 have been isolated in almost quantitative yield. Interestingly, treatment of the silylene IPr·SiCl2 with 1 also affords 3, where silylene insertion into a C–H bond is observed. Computational analysis shows a high energy barrier for silylene insertion, therefore a protonation–deprotonation mechanism is more likely.

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We investigated [{(Me2NCH2)2(C4H2N)}Li]2 (1) by means of experimental charge density calculations based on the quantum theory of atoms in molecules (QTAIM) and DFT calculations using energy decomposition analysis (EDA).

Bis(demethoxy)curcumin (BDMC), extracted from rhizomes of the traditional herb Curcuma longa, has revealed a wide range of medicinal applications, such as antimicrobial and anticarcinogenic. Pure BDMC was obtained by recrystallization from ethanol and three BDMC solvates were identified with acetone, methanol and isopropanol. The crystal structures of pure BDMC and the solvates were resolved by single crystal X-ray diffraction. Analyses of the crystal structures and calculations of crystal packing efficiencies revealed that pure BDMC is efficiently packed. The solvents involved are not utilized to fill the void spaces in the crystal structures, but to provide effective intermolecular interactions. The stoichiometry of the three solvates obtained from single crystal data is 1:1, which is in good agreement with the gravimetric analyses. Furthermore, the desolvation process and stability of the solvates were investigated by various analytical techniques including X-ray diffraction, differential scanning calorimetry, thermogravimetric analyses, hot-stage microscopy and dynamic vapor sorption. Results show that the methanol solvate is more stable compared to the acetone and isopropanol solvates attributed to the strong hydrogen bonding network. Moreover, the desolvation process of the three solvates proceeds through a destructive-reconstructive mechanism.