M. I. Struchkova

The effects of the nature of catalyst and of the solvent on the stereoselectivity in amine-catalyzed asymmetric synthesis of substituted cyclohexa-1,3-dienes from prenal and monoesters of ylidenemalonic acids

In the amine-catalyzed reactions of prenal with (Z)-5-methyl-2-(methoxycarbonyl)hexa-2,4-dienoic or (Z)-3-phenyl-2-(ethoxycarbonyl)prop-2-enoic acid chiral β-amino alcohols provide for higher enantiomeric purity of the resulting alkyl 4-methyl-6-(2-methylprop-1-enyl)-and 4-methyl-6-phenylcyclohexa-1,3-dienoates than that provided by related chiral amines without hydroxy group. The values ofee attained in nonpolar solvents are higher than those observed in the polar ones. Substituting stoichiometric amounts of a chiral 1-amino-3-methylbuta-1,3-diene for a combination of prenal with 0.1 equiv. of the corresponding chiral amine results in the products of much lower enantiomeric purity.

SYNTHESIS AND STRUCTURE OF 2-AMINO-5-AZOLYL-3-CYANO-4H-PYRANS

Previously unknown 5-azolylpyrans were obtained by reactions ofN-acetonyl- andN-phenacylimidazoles, -triazoles, and -tetrazoles with arylmethylenemalononitriles. The structure of 2-amino-3-cyano-6-methyl-5-(5-nitrotetrazol-2-yl)-4-phenyl-4H-pyran was established by X-ray structural analysis.

Chiral complexing agents and phase-transfer agents Communication 2. Synthesis of disubstituted 18-crown-6 ethers with C2 symmetry starting from D-sorbitol

Conclusions(2R,12R)-Disubstituted 18-crown-6 ethers with C2 symmetry containing bulky bicyclic chiral substituents have been obtained from D-sorbitol.

Synthesis of carbonyl compounds based on the products of addition of polyhaloalkanes to unsaturated systems. Reactions of 1-aryl-5,5-dichloropenta-2,4-dien-1-ones with ethyl acetoacetate

The reactions of 1-aryl-5,5-dichloropenta-2,4-dien-1-ones with ethyl acetoacetate in the presence of EtONa give ethyl 4-aryl-6-(2,2-dichlorovinyl)-4-hydroxy-2-oxocyclohexane-carboxylates. The structures of the reaction products were confirmed by1H and13C NMR spectroscopy and by X-ray diffraction analysis.

Chiral and phase transfer agents

Starting from 1,3∶2,4-di-O-ethylidene-D-glucitol (1), two regioisomeric monoaza-18-crown-6 ethers withC2 symmetry were synthesized. A simple route was suggested for the preparation of a diol that is a convenient intermediate for the synthesis of chiral aza-crown ethers from diol1.

Enhanced reactivity of secondary hydroxyl groups in the O-alkylation of carbohydrate-related primary-secondaryvic-glycols. Regioselective 2-O-benzylation of 1,3:2,4-di-O-ethylidene-D-glucitol

Partial O-alkylation of 1,3:2,4-di-O-ethylidene-D-glucitol (1a), 1,2-O-isopropylidene-3-O-methyl-α-D-glucofuranose (1b), andR-(+)-1-O-benzylglycerol (1c) with benzyl chloride in a KOH/DMSO system results in products of monoalkylation at the secondary (4a–c) and at the primary hydroxyl (2a–c) in ratios of over 95∶5 (a), ∼2∶1 (b), and ∼1∶1 (c), whereas (±)propane-1,2-diol (1d) gives only the product of 1-O-benzylation (2d). A qualitatively similar result is observed upon O-alkylation of diols (1a–e) with 2-methoxyethanol tosylate.

Chiral complex-forming and trans-phase transfer agents. 6.1E and13C NMR study of complex-forming ability of homotopic 18-crown-6-ethers based on D-sorbitol and D-mannitol with chiral ammonium salts

It was found using the1H and13C NMR methods that (2R, 12R)-disubstituted derivatives of 18-crown-6-ether containing the residues of l,3∶2,4-di-O-ethylidene(Ia) and 1,3∶2,4-di-O-benzylidene-D-sorbitol (IIa) as substituents and 1,4∶3,6dianhydro-D-mannito-18-crown-6 (III) form stable 1∶1 complexes with α-phenylethylammonium, O-methyl-α-phenylglycinium, O-methylalaninium, O-methyl-α-phenylalaninium, O-methylglycinium hexafluorophosphates, and display an enantiodifferentiating ability with respect to racemates of these salts. In the extraction of the chiral ammonium salts, coronand (Ia) exhibits a low (DCE 1.091.10) enantioselectivity with respect to (R)-enantiomers of α-phenylethyl ammonium and O-methyl-α-phenylglycinium hexafluorophosphates, while coronand (IIa) displays enantioselectivity with respect to (S)-enantiomer of the latter (DCE 0.82). Coronand (III) does not display enantioselectivity in complexes with racemates of these salts.

Chiral complex-forming and trans-phase transfer agents. 7. Complex forming properties of podands based on 1,4∶3,6-dianhydro-D-mannitol

In their complexation with alkali metal picrates, podands prepared from l,4∶3,6-dianhydro-D-mannitol display affinity to Na and Li cations but virtually do not bind K ions. It was shown using the1H NMR method that these podands form complexes with α-phenylethylammonium perchlorate, the composition and strength of which depends on the nature of the side-chains of the podand. The podands studied are not capable of participating in the enantioselective transfer of the chiral substrate from the aqueous phase into chloroform.

Chiral complex formers and agents for transphase transfer. Communication 3. Synthesis of podands with C2 symmetry and 24-crown-8-ether with D2 symmetry derived from from 1,4; 3,6-dianhydro-D-mannitol

Conclusions1.Podands with C2 symmetry have been synthesized from 1,4;3,6-dianhydro-D-mannitol.2.Bis-(1,4;3,6-dianhydro-D-mannitol)-24-crown-6-ether with D2 symmetry has been synthesized.3.A convenient method of adding ethylene glycol segments of a polyether chain to a dianhydromannitol matrix has been developed; it proceeds via O-alkylation with 2-tetrahydro-pyranyloxy-1-bromoethane in superbasic medium and conversion of the reaction product.