Julian Mirek

MNDO study on relative stabilities of monosubstituted pyridine tautomers

Abstract Relative stabilities of monosubstituted hydroxy-, mercapto- and aminopyridine tautomers have been calculated using the MNDO procedure with a full geometry optimization. In all cases considered the “lactim” tautomers proved to be more stable, in full qualitative agreement with the gas-phase experimental data.

The reaction of indolizines and acetylindolizines with trifluoromethylsulfenyl chloride

Abstract Two trifluoromethylsulfenyl groups were introduced into the 1,3 positions of indolizines by the reaction of trifluoromethylsulfenyl chloride with indolizine and its 2-methyl, 2-phenyl, 2-methyl-3-acetyl and 2-phenyl-3acetyl derivatives

Spiroferrocenophanes. I: 3-Spiro[5]ferrocenophane-1,5-diones from the direct condensation of diacetylferrocene with cycloalkanones

Abstract Condensation of diacetylferrocene with cyclohexanone, alkyl- or phenyl-cyclohexanones and cycloheptanone carried out in DMSO in the presence of KOH afforded 3-spiro[5]ferrocenophane-1,5-diones. Cyclopentanone and cyclooctanone failed to give the spiroferrocenophanediones. The mechanism of the reaction, its limitations and side products are discussed. Detailed analysis of the 1 H NMR and 13 C NMR spectra revealed an influence of the cyclohexane ring substituents on the flexibility of the spiroferrocenophanedione bridge. Fragmentation of the product molecules upon electron impact is also described.

Stereochemistry of the reaction of grignard reagents with 3-aryl-and 3-alkyl-[5]ferrocenophane-1,5-diones

The reaction of Grignard reagents with 30aryl- and 3-alkyl-[5]ferrocenophane-1,5-diones is completely stereospecific giving exclusively derivatives in which the introduced alkyl groups are cis to substituents at C(3). The chair conformation, with strong intramolecular hydrogen bonding, predominates in the hydroxyketones obtained, and this is the only conformer present in the case of the dihydroxy derivatives. The second isomer of the hydroxyketones is also the cis type, but its bridge has a twist conformation.

ON SOME INCORRECTNESS IN THE INTERPRETATION OF RESULTS OF THE REACTION OF SULPHINYLAMINES WITH ALDEHYDES

Abstract In contradiction to reports by others, it was shown that sulphinylamines do not give products of cycloaddition on reaction with aldehydes in aprotic solvents. However, in the presence of a protonogenic agent, crystalline products were precipitated for which an ammonium α-aminosulphonate salt structure was confirmed. These salts are formed as a result of consecutive hydrolysis of sulphinylamines, condensation of aldehydes with the resulting amines, and bisulphite anion addition to Schiff bases.

Differences between the Reaction of 2-Benzylidenecyclopentanone with Malononitrile and the Reaction of Cyclopentylidenemalononitrile with Aromatic Aldehydes; Synthesis of Strong Fluorescent o-Aminonitriles

Abstract It was found that instead of the Knoevenagel condensation of cyclopentylidenemalononitrile with aromatic aldehydes, a complex reaction takes place leading to 5,7-dicyano-1-arylidene-4-arylindanes. The same compounds were formed in the reaction of the cyclopentylidenemalononitrile dimer with aldehydes. It is suggested that the cyclopentylidenem alononitrile dimers undergo an electrocyclic ring opening leading to conjugated triene systems. These species are very reactive intermediates and may react with aldehydes in the next step. Bulky substituents in 2,5-dibenzylidenecyclopentanone hindered its Knoevenagel condensation with malononitrile but did not hinder its Michael addition leading to a 4H -pyrane derivative. Solutions of the obtained o-aminonitriles exhibit strong fluorescence in a variety of solvents.

MNDO Studies on Electron Affinity and Ionization Potentials of Polycyano Derivatives of some Unsaturated Hydrocarbons and Benzene

Semiempirical MNDO calculations with optimization of geometry were carried out for several polycyano derivatives of some unsaturated hydrocarbons and benzene. The results show that the MNDO method overestimates the AEA s (adiabatic electron affinity) by about 0.575 eV. as is seen from the equation AEAexp = 0.998 AEAMNDO - 0.575; R = 0.9995. It was found that there exists a linear correlation between the energies of LUMO and the AEAs of the investigated compounds: AEA = - 1078 LUMO + 0.387; R = 0.9979 for 40 points. MNDO does not show a linear correlation of AEA with IP (ionization potential). Generally, with increasing number of cyano substituents in unsaturated hydrocarbons the energy of HOMO and LUMO decreases, but this may not necessarily be true for higher molecular orbitals.

Semiempirical MNDO and UV Absorption Studies on Tautomerism of 2-Quinolones

Semiempirical MNDO calculations with geometry optimization were carried out for seven 4-X-2-quinolone tautomers (X = H, CH3, Cl, OCH3, N(CH3)2, COOH, COOCH3). The results show that 2-hydroxyquinolines are less stabilized compared to 2-quinoIones than 2-hydroxypyridines vs. 2-pyridones. The earlier estimated correction applied to these MNDO results suggests that 4-X-2-quinolones have lower chemical binding energies than the corresponding 4-X-2- hydroxyquinolines by ca. 2.1-3.3 kcal/mol. It is additionally shown that the substituent in position 4 does not influence significantly the relative stabilities of the tautomers. The results of the calculations are verified by UV absorption studies of diluted decane solutions of 2-quinolones at ca. 120°. CNDO/S-Cl-1 calculations based on the optimal MNDO geometries were carried out for 4-X-2- quinolone tautomers. The results generally agree well with the experimental data. A disagreement of the data for 4-COOR-2-quinolones is rationalized.

Spectroscopic and structural studies of quinoline derivatives—II. Forrier transform i.r. spectroscopy. 1. Rotational isomerism in 3-ethoxycarbonyl-4(1H)-quinolone and some of its substituted derivatives

Abstract Rotational isomerism associated with internal rotation about the ring carbon(3)-ester carbonyl carbon single bond in a series of 3-ethoxycarbonyl-4(1H)-quinolones have been investigated spectroscopically in the solid state using Fourier transform i.r. and laser Raman spectroscopy. Particular attention is given to the 1700, 1300 and 1100 cm −1 spectral regions related primarily to the vibrations of the CO 2 C 2 H 5 group. Within these regions rotational isomerism appeared in the compounds examined. The conformational changes are discussed and evidence is reported for occurrence of the unsubstituted compound 1 itself in the solid state at ambient temperature as an equilibrium mixture of both the s-trans ( 1a ) and s-cis ( 1b ) rotamers (this is in contrast to previous findings), and of its Bz-substituted derivatives.

MNDO Studies on Malononitrile Dimerization

Abstract The reaction path of malononitrile dimerization, the intermediates and the tautomerism of the final product have been investigated by the MNDO method. The results are in good agreement with experimental data. The mechanism has a barrier height of about 88 kJ/mol and involves an intermediate which passes to the most stable tautomer through intermolecular proton transfer.