Manfred Steimann

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Starting with its discovery [1] and correct structural assignment [2], Meldrum’s acid (1) has become a widely used reagent in organic synthesis [3]. In general, nucleophilic attack occurs at the carbonyl carbon atoms followed by ring fragmentation. Under basic conditions, the anion acts as a nucleophile itself to generate methylene Meldrum’s acid (2)(More)
In the title compound, C10H16N2O9S3, the pyrimidine ring of the 1,3-dimethyl barbituric acid moiety has an envelope conformation with the C atom carrying the methyl-sulfonyl and bis-(methyl-sulfon-yl)methyl substituents as the flap. The dihedral angle between mean plane of the pyrimidine ring and the S/C/S plane is 72.4 (3)°. In the crystal, mol-ecules are(More)
The ylides Ph3E-C6H6O4 [3; E As (a), Sb (b), Bi (c)] have been prepared through the reaction of Ph3E and 5-bromo-2,2dimethyl-4,6-dioxo-1,3-dioxin (4) followed by addition of triethylamine in good yields. The crystal structures of 3 are reported. Ein neuer Weg zu ArsoniumStiboniumund Bismutonium-2,2-Dimethyl-4,6-dioxo1,3-dioxamiden die Kristallstrukturen von(More)
The title compound, C18H28N2S2·CHCl3, crystallizes as a zwitterion. The C-S bonds are almost equivalent, with lengths of 1.666 (3) and 1.657 (3) Å. The S-C-S bond angle is expanded to 129.54 (16)° and the N-C-N angle is reduced to the tetra-hedal value of 108.8 (2)°. In the crystal, adjacent mol-ecules are linked via C-H⋯S hydrogen bonds, forming chains(More)
The carbene adducts 3a-c (R 1 = Me, Et, iso-Pr; R2 = Me) are formed from the 2,3-dihydroimidazol-2-ylidenes la-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(More)
The title structure, (C(11)H(20)BrN(2))[Ag(CN)(2))], is built up from an approximately C(2v)-symmetric imidazolium cation and a nearly linear dicyanidoargentate anion [N-Ag-N = 176.6 (9)° and Ag-C-N = 178.8 (9) and 177.2 (11)°]. These two constituents are linked by a remarkably short inter-action between the Br atom of the imidazolium cation [C-Br = 1.85(More)
2-Amino-1,3-dimethylimidazolium 2,2-dimethyl-4,6-dioxo-1,3-dioxanide (6) has been obtained from the reaction of 2,2-dimethyl-4,6-dioxo-1,3dioxan (1, “Meldrum’s acid”) and 2-imino-1,3-dimethylimidazoline (5) in excellent yield. The unit cell of 6 contains two crystallographically independent anions lying on crystallographic mirror planes. The structure of(More)
In the title salt, C(11)H(21)N(2) (+)·C(6)H(5)O(3)S(-), which has two cation-anion pairs in the asymmetric unit, the two imidazolium cations are linked to two separate acceptor O atoms of one of the benzene-sulfonate anions through aromatic C-H⋯O hydrogen bonds, while the second anion is unassociated.
The zwitterionic compounds Im-E-Mel [9, E S (a), Se (b), Te (c), Im 2-{1,3-diisopropyl-4,5-dimethylimidazolium}, Mel 5-{2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylide}] are obtained from the corresponding 2-chalcogeno-1,3-diisopropyl-4,5-dimethylimidazolines 8 and 5-bromo-2,2-dimethyl-4,6-dioxo-1,3-dioxan (7) in the presence of triethylamine in excellent yields.(More)