PubMed Health⌕ Search

Biomedical subjects

Frank Rominger

Publications and source records attributed to Frank Rominger.

At least 19 recordsLinked to original sources
PubMed2006

Bis(tert-butylsulfonyl)ethyne and 1-tert-butylsulfinyl-2-tert-butylsulfonylethyne.

The title compounds are electron-poor ethynes. The structure determination of bis(tert-butylsulfonyl)ethyne, C10H18O4S2, (I), is the first of a bis-sulfonyl-substituted ethyne. The molecule is situated on a crystallographic inversion centre. The S-Csp bond [1.737 (2) A] is the longest of this type reported to date. 1-tert-Butylsulfinyl-2-tert-butylsulfonylethyne, C10H18O3S2, (II), which is basically the same as (I) minus one O atom, crystallizes isomorphous with (I). This results in a nearly equal distribution of the three O atoms over the four possible positions.

Journal Article↗
PubMed2005

Molecular scaffold for the construction of three-armed and cage-like receptors.

An efficient procedure was developed for the synthesis of the C3-symmetric molecular scaffold 2. The latter can easily be converted by a single step into either the three-armed receptors 11-16 or the cage-like receptor 17. X-ray structures were obtained for 2, 11, and 16, which are discussed in regard to their aptitude as receptor platforms. The interaction of the three-armed receptors 12-16 and the cage-like receptor 17 with phloroglucinol was investigated. In accordance with the conclusions obtained from molecular modeling and X-ray crystallographic studies on the host-guest complexes, the three-armed bipyridine receptor 16 exhibits, due to its induced fit, a larger association constant toward phloroglucinol than the cage 17. This new receptor system shows all of the positive features characteristic of 2,4,6-trialkylbenzene receptor systems, such as conformational control by steric gearing, ready availability, and versatility in derivatization. These attributes, combined with the advantageous size of the components, allows this system to be readily tailored to provide receptors for larger, biologically important molecules.

Crystallography, X-Ray↗
PubMed2005

N,N:N',N'-Bis(2,2'-dihydroxybiphenyl-3,3'-dimethylidene)benzene-1,2-diamine dimethyl sulfoxide tetrasolvate.

The title compound, 8,15,28,35-tetraazaheptacyclo[35.3.1.1(2,6).1(17,21).1(22,26).0(9,14).0(29,34)]tetraconta-1(41),2,4,6(42),7,9,11,13,15,17,19,21(43),22,24,26(44),27,29,31,33,35,37,39-docosaene-41,42,43,44-tetrol dimethyl sulfoxide tetrasolvate, C40H28N4O4.4C2H6OS, adopts a chair-shaped C(2h) symmetric conformation with crystallographically imposed inversion symmetry. Four intramolecular hydrogen bonds are observed between phenol O and imine N atoms.

Journal Article↗
PubMed2005

Sterically stabilized cyclopropenonophanes and an electronically stabilized cyclopropenethionophane: syntheses, structural properties, and reactivity.

The syntheses of sterically stabilized cyclopropenonophanes as well as an electronically stabilized cyclopropenethionophane are reported, and their molecular structures in the solid state are elucidated. The sulfur of the CS moiety in cyclopropenethiones was shown to react as a nucleophile. Temperatures of more than 240 degrees C favor the extrusion of CO in the cyclopropenonophane to afford an alpha,alpha'-tetramethyl-substituted cyclodiyne. [reaction: see text]

Journal Article↗
PubMed2004

Ligand bite governs enantioselectivity: electronic and steric control in Pd-catalyzed allylic alkylations by modular fenchyl phosphinites (FENOPs).

Modular fenchyl phosphinites (FENOPs) containing different aryl units-phenyl (1), 2-anisyl (2), or 2-pyridyl (3)-are efficiently accessible from (-)-fenchone. For comparison of the influence of the different aryl units on enantioselectivities and reactivities, these FENOPs were employed in Pd-catalyzed allylic alkylations. The strongly chelating character of P,N-bidentate 3 is apparent from X-ray structures with PdCl2 ([Pd3Cl2]), and with allyl-Pd units in ([Pd3(eta1-allyl)] and [Pd3(eta3-allyl)]). FENOP3 gives rise to a PdL* catalyst of moderate enantioselectivity (42 % ee, R product). Surprisingly, higher enantioselectivities are found for the hemilabile, monodentate FENOPs 1 (83 % ee, S enantiomer) and 2 (69 % ee, S enantiomer). Only small amounts of 1 or 2 generate selective PdL* catalysts, while complete abolition of enantioselectivity appears with unselective PdL*2 species with higher FENOP concentrations in the cases of 1 or 2. Computational transition structure analyses reveal steric and electronic origins of enantioselectivities. The nucleophile is electronically guided trans to phosphorus. endo-Allyl arrangements are favored over exo-allyl orientations for 1 and 2 due to Pd-pi-pyridyl interactions with short "side-on" Pd-aryl interactions. More remote "edge-on" Pd-pi-aryl interactions in 3 with Pd-N(lp) coordination favor endo-allyl units slightly more and explain the switch of enantioselectivity from 1 (S) and 2 (S) to 3 (R).

Journal Article↗
PubMed2004

A C3-symmetric molecular scaffold for the construction of large receptors.

A novel C3-symmetric scaffold has been efficiently synthesized exhibiting the property that variable receptor arms can be easily attached by simple alkylation reactions; the utility of the scaffold as a skeleton for large receptors has been examined with a corresponding tris(bipyridyl) derivative toward phloroglucinol.

Journal Article↗
PubMed2004

Cyclic tetra- and hexaynes containing 1,4-donor-substituted butadiyne units: synthesis and supramolecular organization.

Cyclic bis(1,3-butadiynes) with sulfur centers placed in the alpha-position to the 1,3-butadiyne units (2(n)) were synthesized by Glaser coupling of the corresponding open chain dithia-alpha,omega-diynes 1(n). In a second protocol we applied a four-component cyclization by reacting alpha,omega-dithiocyanatoalkanes 6(n) or alpha,omega-diselenocyanatoalkanes 7(n) with dilithium-1,3-butadiynide. This concept afforded either the cyclic dimers (S, 2(n); Se, 9(n)) or the cyclic trimers (S, 8(n); Se, 10(n)). Most of the molecular structures of 2(n) and 9(n) adopt chairlike conformations in the solid state. Tubular structures in the solid state with short distances between the chalcogen centers of neighboring stacks were encountered for 2(5), 9(5), 8(4), 10(4), and 10(5). Recrystallization of 10(5) from various polar and nonpolar solvents yielded inclusion of the solvent guest molecules. The solvent-accessible volume was calculated to vary from 19% (n-hexane) to 25% (mesitylene). The elastic properties of our cycles are due to the flexible methylene chains and the easily variable torsional angles between the rigid 1,3-butadiyne rods.

Journal Article↗
PubMed2004

Hexasubstituted donor-acceptor benzenes as nonlinear optically active molecules with multiple charge-transfer transitions.

The synthesis of three novel nonlinear optical (NLO) chromophores with threefold symmetry, namely 1,3,5-tris(4-N,N-diethylaminophenyl)-2,4,6-tris(4-nitrophenyl)benzene (3), 1,3,5-tris(4-N,N-dihexylaminophenylbutadiynyl)-2,4,6-tris(4-nitrophenyl)benzene (13) and 1,3,5-tris(4-N,N-dihexylaminophenylethynyl)-2,4,6-tris(4-nitrophenylethynyl)benzene (4 b), is reported. We used the [Co(2)(CO)(8)]-catalysed trimerisation of 4-N,N-diethylamino-4'-nitrotolane (5) to prepare 3. The trimerisation experiment carried out with 1-(4-N,N-diethylaminophenyl)-6-(4-N,N-nitrophenyl)hexatriyne (6) and [Rh(PPh(3))(3)Cl] afforded 13. A stepwise approach was used to prepare 4 b. 1,3,5-Trichloro-2,4,6-triiodobenzene (8 b) was coupled with 4-nitrophenyl-acetylene (14) under Pd(0) catalysis to yield 1,3,5-trichloro-2,4,6-tris(4-nitrophenylethynyl)benzene (15). The coupling reaction of 15 with 4-N,N-dihexylaminophenylethynyltributylstannane (21) led to 4 b. X-ray investigations on 3, 4 b and 13 confirmed the structural assignments and revealed that the peripheral aryl rings in 4 b are less twisted around the connecting bonds than in 3 and 13. A large second-order polarisability (beta) of 4 b relative to 3 and 13 was determined by hyper-Rayleigh scattering (HRS). Compound 4 b represents an NLO chromophore with second-order polarisabily among the highest obtained so far for two-dimensional nondipolar NLO chromophores.

Journal Article↗
PubMed2004

A new totally flat N(sp(2))C(sp(2))N(sp(2)) pincer palladacycle: synthesis and photoluminescent properties.

The Sonogashira coupling of 2-bromopyridine with 8-quinolinyl-acetylene affords 2-pyridinyl-8-quinolinyl-acetylene (1) in high yields. The chloropalladation of 1 with Li(2)PdCl(4) in methanol at room temperature affords the pincer palladacycle (C(5)H(4)N-2-C=C(Cl)-8-C(9)H(6)kappaN,kappaC,kappaN)PdCl (2) in 63% yield. The X-ray molecular structure of (2) shows that it is totally flat and that it is associated in pairs though pi-stacking between alternate pyridine-quinoline moieties (3.448 A). The pairs are also connected by pi-stacking with an interpair distance of 3.452 A between quinoline-quinoline moieties. A very low fluorescence emission was also revealed by the pincer palladacycle 2 in both solution and the solid state, which has been ascribed to an excimeric emission due to the particular structure (rigid and totally flat) of 2 in the solid state.

Journal Article↗