Julia Bąkowicz

Monoimine derived from trans-1,2-diaminocyclohexane and ethyl glyoxylate: an intermediate in aza-Diels-Alder and Mannich reactions.

Novel enantiopure policyclic nitrogen heterocycles have been obtained in the diastereoselective aza-Diels-Alder or Mannich reaction of dienes with imine formed in situ from ethyl glyoxylate and (1R,2R)-diaminocyclohexane.

Monitoring structural transformations in crystals. 11. Yang photocyclizations – one type of reaction, but diversity of structural changes

Structural changes proceeding in a crystal during the Yang photocyclization of the salt 6,6-diethyl-5-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylate with (1S)-1-(4-methylphenyl)ethylamine were monitored by means of X-ray structure analysis. The course of the photoreaction was evaluated on the basis of the geometrical parameters for the pure reactant crystal. Variations in the cell constants, the product content, the geometry of the reaction centre, the orientation of molecular fragments and the geometry of hydrogen bonds were described and analyzed. It was found that the cell volume increased until 56% product content and decreased thereafter. The distance between the directly reacting C atoms was constant, approximately 3.0 A, until approximately 75% reaction progress. Analysis of the distance between atoms that would participate in the formation of the second (unobserved) enantiomorph excluded the formation of such an isomer. Molecular fragments varied their orientation during the photoreaction, and the largest change was observed for the carboxylate group despite its participation in strong hydrogen bonds. The geometry of the hydrogen bonds changed during the photoreaction. The largest change was 0.17 A for the D...A distance and 13 degrees for the D-H...A angle. A comparison of the intra- and intermolecular parameters for the studied salt with data for other compounds undergoing the Yang photocyclization in crystals revealed a diversity of structural changes brought about by this type of photochemical reaction.

Structural transformations in crystals induced by radiation and pressure. Part 2. The path of a photochemical intramolecular reaction in crystals at different pressures

Studies have revealed how pressure influences the path of one photochemical reaction in crystals. The single-crystal-to-single-crystal Norrish–Yang reaction of 4-(2,4,6-triisopropylbenzoyl)benzoate benzylammonium, compound 1, was studied at high pressures of 0.3 and 0.9 GPa. X-ray structure analysis was used in order to monitor the kinetics of the reaction and the structural changes induced by UV radiation and pressure. The reaction rate is lower at higher pressure: the rate constants are 5.3 × 10−5 s−1 and 4.3 × 10−6 s−1 at 0.3 and 0.9 GPa, respectively. This was rationalized by: (a) the decrease in the size of voids near the reaction centre and in the unit cell with pressure, (b) the increase of intermolecular interactions in which the photoreactive o-isopropyl group takes part along with pressure and (c) the structural changes brought about by the photochemical reaction itself, for example, the increase of the unit cell volume. Pressure significantly reduced these structural changes and even halted some of them.

Photo-induced structural changes in two crystal forms with different numbers of independent molecules

Structural changes brought about by the Norrish-Yang reaction proceeding in two crystal forms of methyl 2-{[4-(2,4,6-triisopropylbenzoyl)benzoyl]amino}-3-phenylpropanoate were monitored by X-ray structure analysis. The S-enantiomer and the racemic mixture of the compound crystallize in the space groupsP212121 with one molecule in the asymmetric unit and Pna21 with two symmetrically independent molecules, respectively. The changes in the cell volume for both crystal forms are of different kinds. They were attributed not only to the photochemical reaction but additionally to a loss of translational order in the racemic crystal. The structures determined for the partly reacted racemic crystal revealed that two symmetrically independent molecules react at different rates. This fact was explained quantitatively by means of differences in the free space and in the geometry of both molecules. It was also shown that only a single o-isopropyl group took part in the reaction.

Monitoring reaction centers and molecules during an enantioselective photoreaction in a crystal

The single crystal-to-single crystal retro-Claisen photorearrangement of the salt of 7-(4-carboxybenzoyl)norbornene with (S)-(−)-1-cyclohexylethylamine was studied. Although this reaction is an ionic chiral auxiliary-mediated asymmetric synthesis, which normally affords highly enantio-enriched products, the enantiomeric excess in this case is a relatively low 60% (80% of one enantiomer, 20% of the other). X-ray structure analysis was used in order to describe changes in the reaction centers and the behavior of molecules during the photoreaction and to understand the formation of two enantiomers. It was discovered that the conformation of the reactant molecules changes during the photoreaction to one that enables the formation of the minor enantiomer. This was seen clearly at ca. 30% reaction progress. The variations in the cell constants as a function of reaction progress are also presented. The structural changes taking place during the retro-Claisen photorearrangement are compared to the changes observed for other intra- and intermolecular photoreactions in crystals.

Site and stereoselectivity in sulfa-Michael addition to equivocally activated conjugated dienes

The regiochemical course of sulfa-Michael addition of thiols to terminally divergently activated dienes partially incorporated in a cyclic system, as in substituted 2-(3-oxocyclohexenyl)-vinyls, can be to some extent altered by the choice of activation method. The ratio of products of competing 1,4- and 1,6-addition reactions is dependent on the potency of the electron withdrawing group. The iminium ion catalysis favors 1,6-addition to the cyclic ketone group, changing the product preference for dienes terminated with ketone and aryl ester groups. Application of 9-epi-aminoquinine analogues and an acid allowed for both regioselective and enantioselective (up to 90% ee) addition at the distant δ position.

Structural transformations in crystals induced by radiation and pressure. Part 1. How pressure influences the intramolecular photochemical reactions in crystals

The main aim of the studies in this paper is to gain knowledge on the path of structural transformations resulting from the photocyclization in 2-tert-butylphenylphenylmethanone crystals at low and high pressures and also to carry out a comparative analysis of the results at different pressures. This work is the first example of these types of studies in scientific literature. We determined the structure of: pure reactant crystals, i.e. only containing reactant molecules, at 0.1 MPa, 0.55 GPa, 1.27 GPa and 1.50 GPa; pure product crystals, i.e. only containing product molecules, at 0.55 GPa and 1.27 GPa; and partly reacted crystals (ten structures), i.e. containing both reactant and product molecules in various proportions to each other, at 0.1 MPa (two structures), 0.55 GPa (three structures), 1.27 GPa (three structures) and 1.50 GPa (two structures). The studies have shown that (a) there is no phase transition when an increase in pressure is imposed onto the crystals, (b) the unit cell parameters change non-linearly with an increase in pressure, (c) the photochemical reaction was conducted in a homogeneous manner in the examined crystals, (d) the reaction brings about different modes of changes in the unit cell parameters at different pressures (e) the reaction proceeds faster at the end rather than at the beginning regardless of the pressure imposed onto the crystals.

Monitoring Structural Transformations in Crystals. Part 15. Structural Changes in Crystals Caused by UV Radiation Despite the Lack of a Photochemical Reaction

Crystals of 3-benzoylbicyclo[2.2.1]heptane-2-carboxylic acid (C15H16O3) do not undergo the photochemical reaction, namely the Yang photocyclization, but they undergo UV radiation damage. The initial stages of this process were monitored by X-ray diffraction and structure analysis. The results show that the process is smooth and accompanied by the decrease of the overall scale factor, the certain increase of width of reflections, the increase of the cell parameters, intermolecular distances, atomic displacement parameters and the small changes in orientation of molecular fragments.Graphical Abstract

μ-trans-1,2-Di-4-pyridylethene-κ2N:N′-bis­[(dimethyl­formamide-κO)bis­(tri-tert-butoxy­silanethiol­ato-κS)cadmium(II)]

In the centrosymmetric title complex, [Cd2(C12H27O3SSi)4(C3H7NO)2(C12H10N2)], the Cd atom is four-coordinated in a CdNOS2 core.

Influence of pressure on molecular packing and photochemical properties in three chalcone analogs

Abstract The structures of 1-(4-methylphenyl)-3-(2-thienyl)prop-2-en-1-one, (I), 1-(5-bromo-2-hydroxyphenyl)-3-(2-furyl)prop-2-en-1-one, (II), and 1-(3-furyl)-3-[3-(trifluoromethyl)phenyl]prop-2-en-1-one, (III), were determined in ambient and high pressure conditions. The values of the intermolecular geometrical parameters describing possibilities of execution of [2+2] photodimerization were calculated and analysed. In the case of ambient pressure, for (I) they are close to the border valid for photoreactive compounds and for (II) and (III) they exclude the photochemical reaction in crystals. High pressure hardly changed the mutual orientation of adjacent molecules and largely the distance between them: in the case of (I), the distance was far below limits for compounds undergoing [2+2] photodimerization. The volume of free space was calculated for the studied compounds for different values of pressure and analysed in the context of possibilities of the [2+2] photodimerization.