Jana Hodačová

(3+3)-Cyclocondensation of the enantiopure and racemic forms of trans-1,2-diaminocyclohexane with terephthaldehyde. Formation of diastereomeric molecular triangles and their stereoselective solid-state stacking into microporous chiral columns

Abstract The non-templated reaction of both the homochiral as well as the racemic form of trans-1,2-diaminocyclohexane with terephthaldehyde affords (3+3)-cyclocondensed molecular triangles in practically quantitative yields. The configuration of the diastereomeric products resulting in the individual reactions has been determined by 1H and 13C NMR spectroscopy. Unambiguous proof has been obtained by X-ray crystal structure analysis of both alternative diastereomers, revealing also a stereoselective stacking of the triangles into microporous chiral columns.

Click approaches to functional water-sensitive organotriethoxysilanes.

The derivatization of functional organic fragments with triethoxysilyl groups to afford hydrolyzable organosilanes with targeted properties using the copper-catalyzed alkyne azide cycloaddition reaction under strictly anhydrous conditions is described according to two approaches, starting from five silylated substrates. This high yield, fast, and selective method is applicable to a wide range of substrates and is expected to lead to important achievements in the field of functional hybrid silica.

A General Method for Preparing Bridged Organosilanes with Pendant Functional Groups and Functional Mesoporous Organosilicas

New organosilica precursors containing two triethoxysilyl groups suitable for the organosilica material formation through the sol-gel process were designed and synthesised. These precursors display alkyne or azide groups for attaching targeted functional groups by copper-catalysed azide-alkyne cycloaddition (CuAAC) and can be used for the preparation of functional organosilicas following two strategies: 1) the functional group is first appended by CuAAC under anhydrous conditions, then the functional material is prepared by the sol-gel process; 2) the precursor is first subjected to the sol-gel process, producing porous, clickable bridged silsesquioxanes or periodic mesoporous organosilicas (PMOs), then the desired functional groups are attached by means of CuAAC. Herein, we show the feasibility of both approaches. A series of bridged bis(triethoxysilane)s with different pending organic moieties was prepared, demonstrating the compatibility of the first approach with many functional groups. In particular, we demonstrate that organic functional molecules bearing only one derivatisation site can be used to produce bridged organosilanes and bridged silsesquioxanes. In the second approach, clickable PMOs and porous bridged silsesquioxanes were prepared from the alkyne- or azide-containing precursors, and thereafter, functionalised with complementary model azide- or alkyne-containing molecules. These results confirmed the potential of this approach as a general methodology for preparing functional organosilicas with high loadings of functional groups. Both approaches give rise to a wide range of new functional organosilica materials.

Click approaches in sol-gel chemistry

The combination of the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction with sol–gel processing enables the versatile preparation of sol–gel materials under different shapes with targeted functionalities through a diversity-oriented approach. In this account, the development of the CuAAC reaction under anhydrous conditions for the synthesis of sol–gel precursors and for the assembling of magnetic nanoparticles on self-assembled monolayers is related, as well as the use of the classical CuAAC methodologies for the functionalization of mesoporous silica nanoparticles and microdots arrays. Coupling CuAAC and Sol–Gel will result in simplified preparations of multifunctional materials with controlled morphologies.

Copper(ii) and Zn(ii) coordination chemistry of tetraaza[n]cyclophanes

The acid–base behaviour and Zn2+ and Cu2+ metal coordination chemistry of the novel orthocyclophane ligands 2,5,8,11-tetraaza[12]orthocyclophane (L2) and 2,5,9,12-tetraaza[13]orthocyclophane (L3) and metacyclophane 2,5,8,11-tetraaza[12]metacylophane (L1) are studied. Important differences in the chemistry of these compounds are found depending on the substitution of the aromatic ring. The ortho derivatives are much more basic in their first two protonation steps while the metacyclophane presents much larger constants in the third and fourth protonation stages. The crystal structure of the picrate salt of [H2L3]2+ shows an alternate disposition of the protons in the molecule with formation of N–H+⋯N hydrogen bonds between the protonated and non-protonated amino groups. While formation of mononuclear Cu2+ complexes is observed for L2 and L3, the metaderivative L1 forms also binuclear Cu2+ species which predominate largely for molar ratios M∶L 2∶1. The crystal structure of the complex [CuL3Cl](ClO4) shows a chain-like arrangement with the [CuL3]2+ units interconnected by chlorine atoms. The coordination geometry around the metal ion is a distorted octahedron with the nitrogen atoms of the macrocycle at the vertices of the equatorial plane and chloride anions asymmetrically disposed at the axial positions. The Zn2+ complexes of the ortho derivatives L2 and L3 are also much more stable than the meta counterparts. The crystal structure of [ZnL3Cl]Cl·H2O shows a square pyramidal geometry with the nitrogen atoms of the macrocycle at the vertices of the equatorial plane and one chloride anion occupying the axial position. In this case there are not chain arrangements. The involvement of all the nitrogen atoms in the coordination of Zn2+ by L3 in aqueous solution is proved by 1H and 13C NMR.

Synthesis of Rigid Polyaromatic Dialdehydes

Abstract Rigid polyaromatic dialdehydes: biphenyl‐4,4′‐dialdehyde and its longer analogues have been synthesized in high yields by using the Suzuki–Miyaura cross‐coupling reaction. In addition, a novel procedure for a gram‐scale preparation of biphenyl‐4,4′‐dicarbaldehyde from commercially available 4,4′‐bis(chloromethyl)biphenyl has been developed.

C-C Coupling reaction of 1,5-dibromo-2,6-dihydroxynaphthalene with alkali 2-naphthoxide. Opposite effects of counterion coordination and hydrogen bonding on stereoselectivity in the formation of cis- and trans-1,1′:5′,1″-ternaphthyls

Abstract The title reaction yields cis- and trans-2,2′,6′,2″-tetrahydroxy-1,1′:5′,1″-ternaphthyls as the main products. In contrast to non-selective distribution of the stereoisomers in the thermodynamic equilibrium, very high selectivity can be attained under conditions of kinetic control. The observed values of cis-/trans- ratios range between the extremes 94:6 and 6:94, depending on the solvent and counterion employed. The coordination of the metal counterion plays a key role in the reaction performed in toluene, supporting formation of the cis-stereoisomer. When the coordination ability of the counterion is supressed by 18-crown-6, intramolecular hydrogen bonding of the departing bromide group prevails in the stereocontrol, providing support for the trans-stereoisomer formation.

Unprecedented formation of lactone derivatives in thiacalix[4]arene series

Distal bis(carboxymethyloxy) derivatives of thiacalix[4]arene were found to undergo an unprecedented intramolecular cyclisation to yield lactone compounds 5a or 5b, the structure of lactones possessing nine-membered ring was proved by X-ray crystallography; inherent chirality of new compounds was demonstrated using separation on a chiral HPLC column.

Electronic circular dichroism of the chiral rigid tricyclic dilactam with nonplanar tertiary amide groups.

Electronic circular dichroism (ECD) of the spirocyclic dilactam 5,8-diazatricyclo[6,3,0,0(1,5)]undecane-4,9-dione has been measured in the extended wavelength range (170-260 nm) utilizing far-UV CD instrumentation including synchrotron radiation light source. The data of this model of two nonplanar tertiary amide groups interacting within the rigid chiral environment provided new information particularly about the shorter wavelength π-π* transition region below 190 nm. The interpretation using TDDFT calculations confirmed that effects of amide nonplanarity follow our previous observations on monolactams as far as amide n-π* transitions are concerned. ECD band in the n-π* transition region of the nonplanar diamide exhibits an identical bathochromic shift and its sign remains tied to the sense of nonplanar deformation in the same way. As far as n-π* transitions are concerned amide nonplanarity acts as a local phenomenon independently reflecting sum properties of single amide groups. On the other hand, CD bands associated with π-π* transitions (found between ∼170 to 210 nm) form an exciton-like couplet with the sign pattern determined by mutual orientation of the associated electric transition moments. This sign pattern follows predictions pertaining to a coupled oscillator. The influence of amide nonplanarity on π-π* transitions is only minor and concentrates into the shorter wavelength lobe of the π-π* couplet. The detailed analysis of experimental ECD with the aid of TDDFT calculations shows that there is only little interaction between effects of inherent chirality caused by nonplanarity of amide groups and amide-amide coupling. Consequently these two effects can be studied nearly independently using ECD. In addition, the calculations indicate that participation of other type of transitions (n-σ*, π-σ* or Rydberg type transitions) is only minor and is concentrated below 180 nm.