Kalina Kostova

Highly diastereoselective synthesis of new optically active aminoalcohols in one step from (+)-camphor and (−)-fenchone

Abstract New optically active aminoalcohols have been prepared from CeCl 3 -activated (+)-camphor and (−)-fenchone and N-functionalized organolithium compounds. The aminoalcohols obtained catalyze the addition of diethylzinc to benzaldehyde in high yields and enantioselectivities up to 64%.

Anhydrous cerium(III) chloride — Effect of the drying process on activity and efficiency

Abstract The activity and efficiency of anhydrous CeCl3 depend strongly on the drying procedure. Deactivation of CeCl3 occurs during the drying process as a result of hydrolysis by the hydrate water, when heating above 90°C. The highly active CeCl3, prepared by an improved drying procedure, is demonstrated to activate rapidly (in catalytic and stoichiometric amounts) ketones at room temperature, providing excellent addition of organometallic reagents.

Cerium(III) chloride as catalytic and stoichiometric promoter of the quantitative addition of organometallic reagents to (+)-camphor and (-)-fenchone

Quantitative addition of organolithium and Grignard reagents to camphor (1) and fenchone (2) proceeds via precomplexation of the ketone with CeCl3 at room temperature. Excellent addition using catalytic or substoichiometric amounts of CeCl3 is demonstrated for the first time.

Highly effective and practical stereoselective synthesis of new homoallylic alcohols with (+)-camphor and (−)-fenchone skeleton

Abstract The new chiral nonracemic homoallylic exo-alcohols 6, 7, 10 with (1R)-(+)-camphor (1) and endo-alcohols 8, 9, 11 with (1R)-(−)-fenchone (2) skeleton were synthesized in high yields by the stereoselective addition of allyl and substituted allylic Grignard reagents 3–5 to 1 and 2, respectively. The addition of the 2-butenyl (crotyl) reagent 5 occurred with high selectivity leading exclusively to α-methylallyl alcohol 10 with ketone 1 and to (Z)-2-butenyl alcohol 11 with ketone 2. The absolute configurations of the homoallylic alcohols 6–11 were determined by NMR methods.

New bis-steroidal axially chiral diols as ligands for the asymmetric addition of diethylzinc to aldehydes

Abstract New axially chiral steroidal binaphthols, prepared from estrone, were applied in the form of their Ti-alkoxides as catalysts for the addition of diethylzinc to aldehydes. The addition reactions proceeded with high yields and enantioselectivities up to 86%.

Low-cost and sustainable organic thermoelectrics based on low-dimensional molecular metals

Thermoelectric generator composed of crystalline radical ion salts: The unipolar charge transport along the molecular stacks facilitates complementary p- and n-type organic thermoelectric materials of high electrical conductivity and of 1D electronic structure. The specific power output of 5 mW cm-2 and the zT > 0.15 below 40 K demonstrate a new field of low-temperature thermoelectric applications unlocked by organic metals.

Preparation of Chiral Hydroxy Carbonyl Compounds and Diols by Ozonolysis of Olefinic Isoborneol and Fenchol Derivatives: Characterization of Stable Ozonides by1H-,13C-, and17O-NMR and Electrospray Ionization Mass Spectrometry

The allylic and homoallylic alcohols 1 – 8, prepared from (+)-camphor and (−)-fenchone, were ozonized in Et2O at −78° and treated with Et3N or LiAlH4 to give the chiral hydroxy carbonyl compounds 9 – 16 and the diols 17 – 24, respectively (Scheme 1). In the case of the diols 19 and 24, the formation of new chiral centers proceeded with high diastereoselectivity. These diols were prepared highly diastereoselectively also by LiAlH4 reduction of the hydroxy carbonyl compounds 11 and 16a, respectively (Scheme 2). The absolute configuration of the new chiral centers in 19 and 24 was determined by X-ray and NMR methods. The ozonization of compounds 2, 3, 7, and 8 provided the relatively stable hydroxy-substituted 1,2,4-trioxolane derivatives (ozonides) 37 – 40 (Scheme 5) which were characterized by 1H- and 13C-NMR spectra, ESI-MS, and natural-abundance 17O-NMR spectra.

A convenient synthesis of long-chain 4-substituted benzyloxycarbonyl alkanethiols for the formation of self assembled monolayers on metal substrates

New 4-substituted benzyl esters of 16-mercaptohexadecanoic acid were prepared by developing a practicable synthetic procedure and using readily available staring materials. The compounds synthesized have been characterized by NMR, MS, IR spectra and elemental analysis. The mercapto derivatives are precursors for the formation of self-assembled monolayers on metal substrates.

Solid-state tautomerism in 2-carboxyindan-1,3-dione.

The structure of 2-carboxyindan-1,3-dione was investigated using a combination of quantum-chemical calculations and solid-state NMR and IR spectroscopy. Due to poor solubility of the compound in different solvents, no single crystals could be obtained. Two dimeric structures formed from the tautomers of 2-carboxyindan-1,3-dione are likely to coexist in the solid state. The dimers interconvert via intramolecular proton transfer in one of the tautomeric forms constituting the dimers. The energy barrier of the intramolecular proton transfer reaction is calculated as 5.82 kcal mol(-1) at the MP2/6-31++G level of theory.

1-Norbornyllithium as a Precursor for the Synthesis of Novel Organic 1-Bicyclo[2.2.1]Heptane Derivatives and for the Improved Preparation of 1-Chloro-Bicyclo[2.2.2]octane

Abstract An improved strategy for synthesis of 1-chloro-bicyclo[2.2.2]octane is described in which the key compounds 1-norborny substituted ethyl formate(3) or 1-norbornylcarbaldehyde (7) were prepared from 1-norbornyllithium(1). The latter appeared as a useful precursor for the synthesis of various organic bridgehead substituted derivatives.