Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subse... more Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H(2)L((S,S)) (3 a-c) with different substitution patterns. Reaction of these C(2)-symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4-8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu(4)(L((S,S)))(2)(OMe)(4)] (4 a-c) or dinuclear copper(II) helicates (P)-[Cu(2)(L((S,S)))(2)] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd(2)(L((S,S)))(2)] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H(2)L((S,S)) (3 a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(LiMeOH)(2) subset{(Delta,Lambda)-Ni(2)(L((S,S)))(2)(OMe)(2)}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4-8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4 a and palladium(II) helicate 6.
Recently, we reported the template syntheses of the six-and eight-membered iron coronates {M⊂[Fe ... more Recently, we reported the template syntheses of the six-and eight-membered iron coronates {M⊂[Fe n (L 1 ) n ]} + {M=Na, n=6; M=Cs, n=8; (L 1 ) 3− =N[(CH 2 ) 2 O − ] 3 } from iron(III) chloride and triethanolamine.1 In contrast, the six-membered iron coronands [Fe 6 (L 2 ) 6 Cl 6 ] ...
Dedicated to Professor Bernt Krebs on the occasion of his 70th birthday There are two classes of ... more Dedicated to Professor Bernt Krebs on the occasion of his 70th birthday There are two classes of well known T-symmetric complexes, in which four octahedrally coordinated metal ions are located in the apices of a tetrahedron, and each of the six edges are bridged by linear C 2-symmetric bis(bidentate) chelators (L 1) 2À and (L 2) 4À. In [Cs&{Fe II
ABSTRACT Fäden aus Caesiumionen von atomarem Durchmesser können durch supramolekulare Koordinatio... more ABSTRACT Fäden aus Caesiumionen von atomarem Durchmesser können durch supramolekulare Koordinationschemie in einer Eintopfsynthese hergestellt werden. Die Caesiumionen sind in geringen Abständen wie bei einer Perlenkette aufgefädelt. Abgebildet sind das Kalottenmodell der dikationischen Wiederholungseinheit eines eindimensionalen Koordinationspolymers (links) und die unkoordinierten Caesiumstränge in der Elementarzelle (rechts; C schwarz, Cs grün, Cu gelb, O rot, N blau).
ABSTRACT New, diversely substituted phenolic oxazolines were prepd. by two complementary routes s... more ABSTRACT New, diversely substituted phenolic oxazolines were prepd. by two complementary routes starting from salicylic derivs. and various enantiomerically pure 1,2-amino alcs. On one route, 1,2-amino alcs. were directly condensed with salicylic acid derivs., using the Appel reaction, whereas in the other route amino alcs. were treated with the 2-hydroxybenzonitriles under Witte-Seeliger conditions. The latter route was advantageous for L-valinol and L-tert-leucinol, while the first route was the method of choice for new, sterically demanding amino alcs. prepd. from D-serine and L-serine. A nitro group in salicylic derivs. was introduced by means of a regiospecific ipso-substitution of a tert-Bu group by nitric acid. The structure of one nitro product was unambiguously assigned by NOE spectroscopy on the basis of the recently developed DPFGSE-ROE pulse sequence. [on SciFinder(R)]
Angewandte Chemie International Edition in English, 1994
F(000)=1640. L=71.073pm, 7 = ~ 120 C. p(MoK,) = 1.256 mm-I. crystal dimensions: 0.6 x 0.6 x 0.4 m... more F(000)=1640. L=71.073pm, 7 = ~ 120 C. p(MoK,) = 1.256 mm-I. crystal dimensions: 0.6 x 0.6 x 0.4 mm. 4 < 20 I 50 ; of 5491 measured retlections. 5084 were independent and 5080 wwe used for the refinement of 38X paramters: maximum residual electron density: 1572 enm-'. Rl(F>4u(F)) = 0.039, n-R2 = 0.115 (all data) with Kl = ZlIfi;,l-~F c J~X~F o~ and wR2 = (~, i. (F~-~~) z~~,~~F~) 2) * '. The data here collected on a Stoe-Huher diffractometer. The intensity measurements were carried out on a rapidly cooled crystal in the oil drop 1261 by the 28iw method. Semiempirical absorption corrections were carried out on all data. Thc hlructui-e was solved by Patterson and Fourier methods (SHELXS-YO) 1271 and refined with the least squares method on F Z 1281. The refinement of the inxrbion twin parameter [29] (. Y = O.OO(2) for .Y = 0 for the correct absolute structure and .\ = + 1 for the inverted structure) confirmed the absolute structure of 9. Further details of the crystal structure investigation are available on rcqiiebt from the Director of the Cambridge Crystallographic Data Centre. 12 Union Road. GB-Camhrid_ee CB2 1EZ (UK), on quoting the full journal citation.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subse... more Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H(2)L((S,S)) (3 a-c) with different substitution patterns. Reaction of these C(2)-symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4-8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu(4)(L((S,S)))(2)(OMe)(4)] (4 a-c) or dinuclear copper(II) helicates (P)-[Cu(2)(L((S,S)))(2)] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd(2)(L((S,S)))(2)] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H(2)L((S,S)) (3 a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(LiMeOH)(2) subset{(Delta,Lambda)-Ni(2)(L((S,S)))(2)(OMe)(2)}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4-8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4 a and palladium(II) helicate 6.
Recently, we reported the template syntheses of the six-and eight-membered iron coronates {M⊂[Fe ... more Recently, we reported the template syntheses of the six-and eight-membered iron coronates {M⊂[Fe n (L 1 ) n ]} + {M=Na, n=6; M=Cs, n=8; (L 1 ) 3− =N[(CH 2 ) 2 O − ] 3 } from iron(III) chloride and triethanolamine.1 In contrast, the six-membered iron coronands [Fe 6 (L 2 ) 6 Cl 6 ] ...
Dedicated to Professor Bernt Krebs on the occasion of his 70th birthday There are two classes of ... more Dedicated to Professor Bernt Krebs on the occasion of his 70th birthday There are two classes of well known T-symmetric complexes, in which four octahedrally coordinated metal ions are located in the apices of a tetrahedron, and each of the six edges are bridged by linear C 2-symmetric bis(bidentate) chelators (L 1) 2À and (L 2) 4À. In [Cs&{Fe II
ABSTRACT Fäden aus Caesiumionen von atomarem Durchmesser können durch supramolekulare Koordinatio... more ABSTRACT Fäden aus Caesiumionen von atomarem Durchmesser können durch supramolekulare Koordinationschemie in einer Eintopfsynthese hergestellt werden. Die Caesiumionen sind in geringen Abständen wie bei einer Perlenkette aufgefädelt. Abgebildet sind das Kalottenmodell der dikationischen Wiederholungseinheit eines eindimensionalen Koordinationspolymers (links) und die unkoordinierten Caesiumstränge in der Elementarzelle (rechts; C schwarz, Cs grün, Cu gelb, O rot, N blau).
ABSTRACT New, diversely substituted phenolic oxazolines were prepd. by two complementary routes s... more ABSTRACT New, diversely substituted phenolic oxazolines were prepd. by two complementary routes starting from salicylic derivs. and various enantiomerically pure 1,2-amino alcs. On one route, 1,2-amino alcs. were directly condensed with salicylic acid derivs., using the Appel reaction, whereas in the other route amino alcs. were treated with the 2-hydroxybenzonitriles under Witte-Seeliger conditions. The latter route was advantageous for L-valinol and L-tert-leucinol, while the first route was the method of choice for new, sterically demanding amino alcs. prepd. from D-serine and L-serine. A nitro group in salicylic derivs. was introduced by means of a regiospecific ipso-substitution of a tert-Bu group by nitric acid. The structure of one nitro product was unambiguously assigned by NOE spectroscopy on the basis of the recently developed DPFGSE-ROE pulse sequence. [on SciFinder(R)]
Angewandte Chemie International Edition in English, 1994
F(000)=1640. L=71.073pm, 7 = ~ 120 C. p(MoK,) = 1.256 mm-I. crystal dimensions: 0.6 x 0.6 x 0.4 m... more F(000)=1640. L=71.073pm, 7 = ~ 120 C. p(MoK,) = 1.256 mm-I. crystal dimensions: 0.6 x 0.6 x 0.4 mm. 4 < 20 I 50 ; of 5491 measured retlections. 5084 were independent and 5080 wwe used for the refinement of 38X paramters: maximum residual electron density: 1572 enm-'. Rl(F>4u(F)) = 0.039, n-R2 = 0.115 (all data) with Kl = ZlIfi;,l-~F c J~X~F o~ and wR2 = (~, i. (F~-~~) z~~,~~F~) 2) * '. The data here collected on a Stoe-Huher diffractometer. The intensity measurements were carried out on a rapidly cooled crystal in the oil drop 1261 by the 28iw method. Semiempirical absorption corrections were carried out on all data. Thc hlructui-e was solved by Patterson and Fourier methods (SHELXS-YO) 1271 and refined with the least squares method on F Z 1281. The refinement of the inxrbion twin parameter [29] (. Y = O.OO(2) for .Y = 0 for the correct absolute structure and .\ = + 1 for the inverted structure) confirmed the absolute structure of 9. Further details of the crystal structure investigation are available on rcqiiebt from the Director of the Cambridge Crystallographic Data Centre. 12 Union Road. GB-Camhrid_ee CB2 1EZ (UK), on quoting the full journal citation.
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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Papers by Rolf Saalfrank