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 alpha-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.

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 degrees 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. Copyright (C) 1996 Elsevier Science Ltd

New optically active aminoalcohols have been prepared from CeCl3-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%. (C) 1997 Elsevier Science Ltd.

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 I). In the case of the diols 19 and WI 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 H-1- and C-13-NMR spectra. ESI-MS, and natural-abundance O-17-NMR spectra.

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%. (C) 2000 Elsevier Science Ltd. All rights reserved.

Detailed investigation of the tautomerism of oxazolidines, thiazolidines and selenazolidines substituted at positions 2 and 4 by hydroxy and amino groups was carried out by calculations at HF and MP2 levels of theory and NMR spectroscopy. The relative stabilities of the tautomers of the heterocycles were calculated in gas phase and in solvents CHCl3 and DMSO utilizing the PCM method. The ab initio calculations, in agreement with the available experimental data, predict that the azolidines substituted at positions 2 and 4 by a hydroxy and an amino group exist as amino form in solution, while 2,4-diamino-oxazolidine, -thiazolidine and -selenazolidine occur as mixtures of tautomers.

New 4-substituted benzyl esters of 16-mereaptohexadecanoic acid were prepared by developing a practicable synthetic procedure and using readily available starting 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. (C) Central European Science Journals. All rights reserved.

In recent years, impressive progress has been made in the development of new chiral ligands and in new methodology for Zn-mediated enantioselective additions to aldehydes. The current report aims to present the recent progress in this field.

The structures of some 2-substituted indan-1,3-diones are investigated in the gas phase and solution using quantum chemical calculations and spectral (NMR, IR, and UV) measurements. The influence of the substituent at the 2-position on the tautomeric equilibrium of 2-substituted indan-1,3-diones in solvents with different polarity is evaluated. It is shown that the equilibrium in 2-formyl-indan-1,3-dione and 2-acetyl-indan-1,3dione is shifted to the 2-hydroxyalkylidene-indan-1,3-dione tautomer, while 2-carboxyamide-indan-1,3-dione exists as a mixture of two tautomers, 2-(hydroxyaminomethylidene)-indan-1,3-dione and 2-carboamide-lhydroxy-3-oxo-indan, with extremely fast proton transfer between them. The situation for 2-carboxy-indan1,3-dione is quite different -on the basis of the analysis of the obtained results, the possible existence of an anionic form of 2-carboxy-indan-1,3-dione in solution can be inferred.