Sirpa Kotila

Self-Assembly of 2,8,14,20-Tetraisobutyl-5,11,17,23-tetrahydroxyresorc[4]arene

We report herein the observation of a hexameric structure of a hydroxyresorc[4]arene in the solid state, enclosing a large interior space. This artificial molecular container is stabilized only by hydrogen bonds. The tendency to form aggregates in solution is demonstrated mainly by means of ESI-MS methods.

A configurationally stable pyrrolohelicene: experimental and theoretical structure-chiroptic relationships

Abstract The sterically overcrowded tetramethyldipyrrolo[6]helicene 2 was prepared by the Bucherer reaction for the first time. While the longest known hexahelicene 1 does not form stable enantiomers at room temperature, 2 could be separated into the antipodes, which is explained by the extremely different racemization barriers of the two compounds (≈60 kJ/mol for 1 , and ≈195 kJ/mol for 2 ). The quantum mechanically calculated and experimentally determined geometries are in good accordance. The strongly deformed helix 2 shows a pitch enlarged by 62 pm compared to the non-substituted compound 1 . Whereas 1 forms intermolecular hydrogen bonds in the solid, the crystal structure of 2 exhibits coordination of clathrated acetone at the NH-groups. Experimental and theoretically simulated CD Spectra of 2 are compared.

Reaction of dimethylzirconocene with imidazole in the presence of tris(pentafluorophenyl)borane

Abstract Dimethylzirconocene ( 1 ) reacts with the imidazole · B(C 6 F 5 ) 3 adduct ( 2 ) to give methane and the methylzirconocene/imidazole/ tris(pentafluorophenyl)borane-betaine complex 3 . Subsequent stoichiometric hydrolysis yields the corresponding dinuclear μ-hydroxy-bridged betaine complex 4 , that was characterized by an X-ray crystal structure analysis.

Synthesis and structural studies of 5, 11, 17, 23-tetrahydroxyresorc[4]arenes

Hydroxyresorc[4]arenes are bowl-shaped calixarene compounds. Herein we report the synthesis and the results of X-ray diffraction examinations of six hydroxyresorc[4]arenes, one of them could be crystallized in two conformations. All compounds co-crystallize with different solvent molecules, linked together by hydrogen bonds. It is known that hydroxyresorc[4]arenes are capable of forming large aggregates, a number of different compounds have been prepared, some of them could be crystallized and investigated by single crystal methods. Most of the compounds tend to form polarity-induced double layers.

Organic syntheses via transition metal complexes. LXXXI. Bis(carbene) complex of chromium connected by a conjugated ammonium pentadienide bridge

Abstract The reaction of pentacarbonyl(1-ethoxyenthylidene)chromium and tetrachlorocyclopropene in the presence of triethylamine affords a bis(carbene) complex 3 , in which the carbene chromium units are connected by a conjugated and planar ammonium pentadienide bridge. According to NMR measurements the compound adopts a fluctional ( Z , E ) configuration. The structure of 3 was established by X-ray structure analysis [C 27 H 27 Ctr 2 NO 12 · 2Ch 2 Cl 2 , triclinic, space group P 1 (No. 2), a = 12.703(1) A , b = 12.847(1) A , c = 13.667(2) A , α = 95.77(1)°, β = 110.15(1)°, γ = 112.81(1)° Z = 2, R = 0.072, wR 2 = 0.201 ].

Counter-ion induced self-assembly of a meso-helicate type molecular box

The self-assembly process of binuclear meso-helicate type coordination compounds from three CH2-bridged bis(catechol) ligands (H4L) and two titanium(IV) ions is induced by Li+ or Na+ but not by K+; in the solid state Li3[L3Ti2]– forms a molecular box.

Synthesis of Azapolycyclic Systems Based on the Indolizino[3,4‐b]quinoline Skeleton − A Diastereoselective Entry to Potential Oligodentate Artificial Receptors

A convenient diastereoselective synthetic route to the molecular tweezer bis(indolizino[3,4-b]quinolyl)methane 9 and the rigid indolizino[7′,8′:2,3]quinolino[8,7-h]indolizino[8,7-b]quinolines 14, 15 as potential receptor molecules has been developed, involving double imine condensation followed by Lewis acid catalyzed biscyclization of prolinal-derived bis(imines) 8 and 13, respectively. Whereas the use of SnCl4 leads to the formation of the planar polycycle 15, the corresponding concave product 14 is formed in the presence of EtAlCl2. Both compounds 14, 15, as well as tweezer 9 have been characterized by X-ray crystal-structure analysis. Although tris(imines) 20, 24 derived from 1,3,5-triaminobenzene (18) and tris(4-aminophenyl)amine (23) could be obtained similarly by molecular sieve-catalyzed condensation, the corresponding triscyclization could not be achieved. However, by attaching preformed indolizino[3,4-b]quinoline subunits 25 and 31 to an aromatic core, the bidentate receptors 30, 33 and the tentacle molecule 28 were accessible.

Enzymatic synthesis of optically active mono-alkylated malonic monoesters

Abstract Pig-liver esterase hydrolysis of tertiary-alkyl malonic diesters 1 leads to malonic monoesters 2 in high yields and with enantiomeric excesses up to 96% ee . The configuration of the new stereogenic carbon atom was determined by crystal structure analysis of the ( S )-1-phenylethylamide of 2b . The monoesters 2 are stable against racemisation between pH 2 to pH 12 as shown for 2b .

Bis(pentamethylcyclopentadienyl)‐Substituted Phosphanes: Synthesis and Structure

The bis(1,2,3,4,5-pentamethyl-1,3-cyclopentadien-1-yl)phosphanes 3−7 are formed in good yields by the reaction of the halogenophosphanes 2a or 2b with the appropriate nucleophile. Following another route, the dialkylaminobis(pentamethylcyclopentadienyl)phosphanes 11a−c have been synthesized by the treatment of dichloro(dialkylamino)phosphanes with two equivalents of (pentamethylcyclopentadienyl)lithium. The compounds 3−11 have been characterized by multinuclear NMR spectroscopy and 3, 5, 6, and 11a have also been characterized by single-crystal X-ray diffraction studies. The molecular structure of 11a is governed by steric congestion, which typically would lead to a parallel arrangement of the two pentamethylcyclopentadienyl ligands at the phosphorus atom. However, surprisingly, the crystal structure of the (dimethylamino)phosphane 11a, exhibits a tilted, rather than a parallel, conformation of the pentamethylcyclopentadienyl groups [tilt angle: 130.6(1)°].

Syntheses and structure of bis(pentamethylcyclopentadienyl)-dithiophosphinato Complexes†

Bis(pentamethylcyclopentadienyl)phosphane Cp*2PH reacts with sulfur under basic conditions to give the corresponding dithiophosphinate salts M+ CP*2PS−2 (5 M+ = HNEt+3, 6 M+ = Li+), which are formed via the intermediate CP*2P(S)H (4). Both salts on treatment with cobalt(II) chloride give rise to the transition metal dithiophosphinate 7. The structures of this new type of diorganodithiophosphinate complexes in the solid state have been investigated.