Áron Szöllösy

Enantioselective Michael reaction of 2-nitropropane with substituted chalcones catalysed by chiral azacrown ethers derived from α-D-glucose

Abstract The chiral monoaza-15-crown-5 lariat ethers anellated to methyl-4,6-O-benzylidene-α- d -glucopyranoside 1a–c showed significant asymmetric induction as phase transfer catalysts in the Michael addition of 2-nitropropane to substituted chalcones. Among the catalysts bearing different side arms at the nitrogen atom, the compound with a phosphinoxidoalkyl side chain 1c proved to be the most effective (max. 78% e.e.). The type of substituent on the chalcone was found to have a very significant influence on both the chemical yield and the enantioselectivity of the reaction. The absolute configuration of the Michael adducts 3b and 3i was determined by chemical methods, while that of 3d was assigned by X-ray crystal structure determination.

Synthesis of Acerogenin C and (+)‐Acerogenin A, Two Macrocyclic Diarylheptanoid Constituents of Acer nikoense

The macrocyclic ketone acerogenin C (3) and the corresponding alcohol (+)-accerogenin A (1), diarylheptanoid constituents of the maple Acer nikoense were synthesized. The key steps were the selective reduction of the double bond of an α,β-unsaturated ketone (10) and macrocyclization of an iodophenol (13) by a modified Ullmann diarylether synthesis.

Isomerization of Substituted Tricyclic 4,5-Dihydropyrazoles

SummaryThe acid and base catalyzed isomerization of some tricyclic 2-pyrazolines with N-Carbamoyl-,N-thiocarbamoyl-and N-phenyl substituents was investigated. Starting fromcis ortrans 3-H, 3a-H diastereomers, equilibrium mixtures ofcis andtrans diastereomers were prepared which were separated and subsequently studied by1H NMR and13C NMR spectroscopy. A mechanism for the isomerization of the pyrazolines is suggested, supported by a deuterium exchange at C-3a.ZusammenfassungDie Isomerisierung einiger tricyclischer 2-Pyrazoline mit N-Carbamoyl-, N-Thiocarbamoyl-und N-Phenyl-substituenten unter saurer und basischer Katalyse wurde untersucht. Ausgehend von dencis odertrans 3-H,3a-H-Diastereomeren wurdencis- undtrans Gleichgewichtsgemische gewonnen, die getrennt und durch1H- und13C-NMR-Spektroskopie untersucht wurden. Ein Mechanismus für die Isomerisierung von Pyrazolinen wird vorgeschlagen, der durch den Deuteriumaustausch in Position 3a-C unterstützt wird.

Fused heterocycles. Part 3. Synthesis and stereochemistry of benzopyrano and benzothiapyrano-[4,3-c]pyrazoles

Several tricyclic benzopyrano[4,3-c]pyrazole derivatives have been studied by 1H and 13C n.m.r. spectroscopy. They were prepared by treating 3-benzylidene-chromanones and -1-thiochromanones with semicarbazide or thiosemicarbazide: reactions which give only the cis 3-H,3a-H stereoisomers.

Fused heterocycles. Part 4. Synthesis and stereochemistry of hexahydrobenzo[6,7]cyclohepta[1,2-c]pyrazoles

Hexahydrobenzo[6,7]cyclohepta[1,2-c]pyrazoles have been synthesized by treating 2-benzylidene-1-benzosuberone with hydrazine derivatives. The cis and trans isomers have been distinguished and conformational equilibria studied by NMR techniques.

Light Induced Reductive Ring Contractions of Sixmembered Cyclic Iminium Ions

Photochemically induced reductive ring contractions, previously observed for 2,5-dihydro-1,2,4-triazines, have also been verified for 1,4-dihydropyrimidines 2a,b, the dihydro-1,2,4,5-tetrazine 9, and dihydro-1,3,5-triazines 11a,b giving rise to fivemembered fully unsaturated heterocycles (pyrroles 4a,b, imidazoles 13a,b, and triazole 10, respectively). The 1,4-dihydropyrazines 15a—j tend to decompose in acidified 2-propanol in the dark, but on irradiation they also undergo reductive ring contraction furnishing solely the 1,2,5- triarylpyrroles 16a—d rather than the (a priori also possible) isomeric 1,3,4-triarylpyrroles 17a/mdash;d. In contrast, the 3,6-diphenylpyrid-azine 18 gives the 4-isopropyl-analogue 19 in low yield upon irradiation in hydrogen chloride saturated 2-propanol.

23Na NMR shift reagents enhance cardiac staircase effect in isolated perfused rat hearts

The effects of the currently used 23Na NMR shift reagents, dysprosium bis‐triphosphate [Dy(PPP)2], dysprosium triethylenetriamine hexaacetate [Dy(TTHA)] and thulium 1,4,7,10‐tetraazacyclododecane‐N,N′,N″,N‴‐tetra(methylenephosphonate) [Tm(DOTP)] were studied in the rat heart cardiac staircase model. Rat hearts were perfused with low or normal extracellular free calcium ([Cao]f). At low [Cao]f (0.34 ± 0.05 mM), hearts were perfused with Dy(PPP)2 (group I), Dy(TTHA) (group II) or no shift reagent (group III), while at normal [Cao]f (1.25 ± 0.15 mM), hearts were perfused with Tm(DOTP) (group IV), Dy(TTHA) (group V) or no shift reagent (group VI). Left ventricular developed pressure (LVDP) values in group I were significantly higher than in groups II and III (p < 0.01), while no significant differences were found between groups II and III. LVDP values in group IV were significantly higher than in groups V and VI (p < 0.05), while the LVDP values in groups V and VI were almost identical. Also, a positive correlation between pacing rate and intracellular sodium ([Nai]) was evident. The [Nai] values at high [Cao]f were significantly lower than at low [Cao]f at each pacing level (p <0.01), indicating a negative correlation between [Nai] and [Cao]f. No statistical differences were found in [Nai] between groups I vs II and IV vs V, showing that determination of [Nai] is not affected by any of these shift reagents. Thus the different LVDP responses in groups I vs II and IV vs V were not mirrored in [Nai] changes. We hypothesize that a direct, sarcolemmal Ca–Dy(PPP)2‐, or Ca–Tm(DOTP)‐induced positive inotropic effect could be responsible for these Nai‐independent LVDP increases in groups I and IV. Copyright

Synthesis, extraction ability and application in an asymmetric synthesis of azacrown ethers derived from D-mannitol

New chiral monoaza-15-crown-5 ethers have been synthesised from 1,2:5,6-di-O-isopropylidene-D-mannitol. The substituent at the nitrogen atom has a major influence on the cation extraction ability of the azacrown. These sugar-based crown ethers show asymmetric induction as chiral phase transfer catalysts in the Michael addition of 2-nitropropane to chalcone (67% ee).

Isomerism of 9-arylaminomethylene-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[1,2-a]pyrimidines

Several 9-arylaminomethylnene-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[1,2-a]pyrimidines have been synthesized and studied by 1H and 13C n.m.r. spectroscopy. The dominant tautomeric form has been established. Fast Z–E isomerisation has been found around the enamino CC double bond. The effect of the solvent, temperature, and various structural modifications on the equilibrium Z : E isomeric ratios has been measured.

Synthesis of functionalized P-heterocycles including phosphine-borane complexes

Abstract Preparation of phosphinic chlorides, amides, and sulfide derivatives, as well as phosphine-borane complexes of P-heterocycles is described.