Cäcilia Maichle-Mößmer

Synthese und Strukturen von Cl3Ti(μ-O)(μ-ImCO2)2TiCl3 und Cl3Ti(μ-O)(μ-ImCO2)TiCl3 · 2 MeCN (Im = 2,3-Dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-yliden): ein Imidazoliumcarboxylat als elektroneutraler Brückenligand [1]

1,3-Diisopropyl-4,5-dimethylimidazolium-2-carboxylat (4, ImCO2) reagiert mit TiCl4 unter Bildung des Komplexes ImCO2 · TiCl4 (5) unbekannter Struktur. 5 wird von Wasser zu den Komplexen Cl3Ti(μ-O)(μ-ImCO2)2 · MeCN (6) und Cl3Ti(μ-O)(μ-ImCO2)TiCl3 · 2 MeCN · 2 CH2Cl2 hydrolysiert. In 6 und 7 agiert ImCO2 nach Aussage von spektroskopischen und strukturellen Daten als elektroneutraler Carboxylato-Ligand. Die Kristallstrukturen von 6 und 7 werden beschrieben. Syntheses and Structures of Cl3Ti(μ-O)(μ-ImCO2)2TiCl3 and Cl3Ti(μ-O)(μ-ImCO2)TiCl3 · 2 MeCN (Im = 2,3-Dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene): an Imidazolium Carboxylate as Electroneutral Bridging Ligand 1,3-Diisopropyl-4,5-dimethylimidazolium-2-carboxylate (4, ImCO2) reacts with TiCl4 to give the complex ImCO2 · TiCl4 (5) of unknown structure. 5 is readily hydrolysed to give the carboxylato complexes Cl3Ti(μ-O)(μ-ImCO2)2TiCl3 · MeCN (6) and Cl3Ti(μ-O)(μ-ImCO2)TiCl3 · 2 MeCN · 2 CH2Cl2 (7). In 6 and 7 ImCO2 acts as an electroneutral carboxylato ligand as indicated by spectroscopic and structural data. The X-ray structures of 6 and 7 are reported.

Nucleophilic Aromatic Substitution with 2,3-Dihydro-1,3-diisopropyl- 4,5-dimethylimidazol-2-ylidene

2,3-Dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (1) reacts with an excess of hexafluorobenzene in the presence of boron trifluoride diethyletherate to give 1,3-diisopropyl-4,5- dimethyl-2-(perfluorophenyl)imidazolium tetrafluoroborate (2). Solutions of 2 exhibit an equilibrium consisting also of hexafluorobenzene and 2,2ʹ-(perfluoro-1,4-phenylene)bis(1,3-diisopropyl- 4,5-dimethylimidazolium)bis(tetrafluoroborate) (3) which is obtained from 1 and hexafluorobenzene in the ratio 2 : 1 on a preparative scale. Similar to 2, 2-(4-cyano-2,3,5,6-tetrafluorophenyl)-1,3- diisopropyl-4,5-dimethylimidazolium tetrafluoroborate (4), 2-(2,4-dicyano-2,5,6-trifluorophenyl)- 1,3-diisopropyl-4,5-dimethylimidazolium tetrafluoroborate (5), and 2-(4,6-difluoro-1,3,5-triazin-2- yl)-1,3-diisopropyl-4,5-dimethylimidazolium tetrafluoroborate (6) are obtained from 1 and perfluorobenzonitrile, 1,3-dicyano-2,4,5,6-tetrafluorobenzene, and 2,4,6-trifluoro-1,3,5-triazin, respectively. The FAB mass spectra of compounds 2 - 6 and the results of the crystal structure analyses of compounds 2 - 4 are discussed. Graphical Abstract Nucleophilic Aromatic Substitution with 2,3-Dihydro-1,3-diisopropyl- 4,5-dimethylimidazol-2-ylidene

Synthesis, Structure and Reactions of 1,3-Dimethyl-5-bis(thiomethyl)methylenebarbituric Acid

1,3-Dimethyl-5-bis(thiomethyl)methylenebarbituric acid (8) is obtained from 1,3-dimethylbarbituric acid and CS2/NEt3 followed by alkylation with methyl iodide. Compound 8 reacts with aqueous ammonia to give 5-amino(thiomethyl)methylene-1,3-dimethylbarbituric acid (9). With benzylamine, the thiomethyl substituent in 9 is replaced to give 5-amino(benzylamino)methylene-1,3- dimethylbarbituric acid (10) while with methanesulfonic acid the sulfonate salt 11 is formed. The crystal structures of 8 and 9 are reported. Graphical Abstract Synthesis, Structure and Reactions of 1,3-Dimethyl-5-bis(thiomethyl)methylenebarbituric Acid

1,3-Dialkyl-5-hydroxy-2-thioxoimidazolidin-4-one / 1,3-Dialkyl-5-hydroxy-2-thioxoimidazolidin-4-ones

The 1,3-dialkyl-5-hydroxy-2-thioxoimidazolidin-4-ones 8 (R = Me, Et, iPr) were obtained from the corresponding thiourea and glyoxylic acid monohydrate in very good yield. Their reactions with chlorotrimethylsilane in the presence of triethylamine gave the 1,3-dialkyl-5-trimethylsiloxy-2-thioxoimidazolidin- 4-ones 9. NMR and crystal structure data of 1,3-diisopropyl-5-hydroxy-4-thioxoimidazolidin-4-one (8c) have confirmed the acyloin-type structure of the above mentioned compounds. Graphical Abstract 1,3-Dialkyl-5-hydroxy-2-thioxoimidazolidin-4-one / 1,3-Dialkyl-5-hydroxy-2-thioxoimidazolidin-4-ones

Bis[1,3-dimethylbarbituryl(5)]sulfid – Struktur und Reaktionen/ Bis[1,3-dimethylbarbituryl(5)]sulfide – Structure and Reactions

Bis[1,3-dimethylbarbituryl(5)]sulfide (3, [BarbH]2S, BarbH = 1,3-dimethylbarbitur-5-yl) was obtained from 1,3-dimethylbarbituric acid (2) and SCl2 or SOCl2. The compound 3 reacted with 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (7, Im) to give the imidazolium salts [ImH][BarbH-S-Barb] (8) and [ImH]2[Barb-S-Barb] (9) in which the ions are linked by hydrogen bonds. From 3 and triphenylphosphane, the zwitterionic compound Barb-S-PPh3 (10) was obtained. The crystal structures of the compounds 3, 8, 9 and 10 were discussed.

Stabile Carben-Addukte des Chlors / Stable Carbene Adducts of Chlorine

Abstract The carbene adducts 3a-c (R1 = Me, Et, iso-Pr; R2 = Me) are formed from the 2,3-dihydro-imidazol-2-ylidenes 1a-c and 1,2-dichloroethane as air-sensitive solids in good yields. The compounds exhibit a reactive Cl-Cl bond. Benzene is chlorinated by 3a,b to give chlorobenzene and the imidazolium salts 10a,b under mild conditions. 3c acts as a chloride donor to give with AICI3 and SO2 the 2-chloroimidazolium salts 12c and 13c (X = AlCl4, SO2Cl). On hydrolysis, the less reactive hydrate salt 14c is formed from 3c. The X-ray structures of 10a and 14c are reported.

Reaction of a Zwitterionic Pyridinium Ylide with N,N-Dimethylaniline

1,3-Dimethyl-2,4,6-trioxo-5-pyridinomethyl-1,3-perhydrodiazin- 5-ylpyridinium ylide (3) reacts with N,N-dimethylaniline to give 5-((1,3-dimethyl-2,4,6-trioxo-hexahydropyrimidin- 5-yl)methyl)-5-(4-(dimethylamino)benzyl)-1,3- dimethylpyrimidine- 2,4,6(1H3H5H)-trione (6) in good yield. The crystal structure of 6 is reported Graphical Abstract Reaction of a Zwitterionic Pyridinium Ylide with N,N-Dimethylaniline

Elimination of a Thiomethyl Substituent from an Anionic 5-Methylenebarbituric Acid Derivative by Oxidation and Substitution

Triethylammonium 5-[(1,3-dimethyl-2,4,6-trioxo-tetrahydropyrimidin-5(6H)-ylidene)-(methylthio) methyl]-1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-olate (5), obtained from 5-[bis (methylthio)methylene]-1,3-dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione (2) and 1,3-dimethylbarbituric acid in the presence of triethylamine, is protonated by methanesulfonic acid to give 5,5ʹ-(methylthiomethanediylidene)bis(1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione) (6) in good yield. Compound 6 is oxidized in two steps by m-chloroperbenzoic acid to give 5,5ʹ- (methylsulfinylmethanediylidene)bis(1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione) (7) and 5-[(1,3-dimethyl-2,4,6-trioxo-tetrahydropyrimidin-5(6H)-ylidene)(methylsulfinyl)methyl]-5-hydroxy- 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (8), respectively. Excess pyridine eliminates methanesulfinic acid from 8 to give the zwitterionic 5-[(1,3-dimethyl-2,4,6-trioxo-tetrahydropyrimidin- 5(6H)-ylidene(pyridinium-1-yl)methyl]-1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydropyrimidin- 4-olate (9). The crystal structures of compounds 6, 8, and 9 are reported. Graphical Abstract Elimination of a Thiomethyl Substituent from an Anionic 5-Methylenebarbituric Acid Derivative by Oxidation and Substitution

Synthesis and Reactions of 5-[Amino(thiomethyl)methylene]- 2,2-dimethyl-1,3-dioxane-4,6-dione

5-[Amino(thiomethyl)methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione (4) is obtained from 5-[bis- (thiomethyl)methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione (1) and aqueous ammonia in excellent yield. Its reaction with m-chloroperbenzoic acid gives the sulfoxide derivative 5-[amino(sulfinylmethyl) methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione (5). With triphenylphosphine, 5 reacts to give triphenyl( thiomethyl)phosphonium 5-cyano-2,2-dimethyl-1,3-dioxane-4,6-dionate (6) from which the methyltriphenylphosphonium salt 6a is obtained with excess triphenylphosphine. The crystal structures of 4, 5 and 6a are discussed. Graphical Abstract Synthesis and Reactions of 5-[Amino(thiomethyl)methylene]- 2,2-dimethyl-1,3-dioxane-4,6-dione

C–H···O-Brückenbindungen in Imidazolium-Carboxylaten / C–H···O Hydrogen Bonds in Imidazolium Carboxylates

2,3-Dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (1) reacts with benzoic acid to give the corresponding 1,3-diisopropyl-4,5-dimethylimidazolium benzoate salt 2. Similarly, 1,3-diisopropyl-4,5-dimethylimidazolium formiate (3) is obtained from 1 and ammonium formiate. In crystals of 2, the anions are linked to the imidazolium ions by monofunctional O···H-C bonds while in 3 bifurcated O・・・H-C bonds are observed. In 1,3-diisopropyl-4,5-dimethylimidazolium hydrogenoxalate (4), obtained from 1 and oxalic acid, hydrogen bonds connect both imidazolium ions to the hydrogenoxalate ions in a bifurcated mode as well as the anions to each other.