Zur Stereochemie des Te(IV) gegenüber Sauerstoff

Zusammenfassung Die Koordination von Sauerstoff um Te(IV) zeigt in Kristallstrukturen eine Besonderheit, welche bisher nicht erkannt worden zu sein scheint: Während die Konfiguration von Te(IV) mit seinen drei nächsten Nachbarn in Bindungslängen und Bindungswinkeln recht konstant ist, variiert die Länge der viertnächsten Te–O-Bindung stark (von 2.08 bis 2.98 Å); dennoch ist ihre Richtung bemerkenswert konstant, wenn man Te–O-Abstände größer als 2.75 Å vernachlässigt. Auch die Richtungen zu weiteren Sauerstoff-Nachbarn (bis 3.0 Å) sind nicht statistisch verteilt, sondern gewisse räumliche Bereiche werden vermieden. Es wird versucht, diese phänomenologischen Befunde zu interpretieren.

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Contributions to the stereochemistry of Te(IV) towards oxygen

In crystal structures, the coordination of oxygen around Te(IV) shows a peculiarity which does not seem to have been recognized by now: While the configuration of Te(IV) with its three nearest neighbours is relatively constant as to bond lengths and bond angles, the length of the forth Te–O-bond varies greatly (from 2.08 to 2.98 Å); its direction, however, is remarkably constant if one excludes Te–O-distances larger than 2.75 Å. Also the directions to additional oxygen neighbours (up to 3.0 Å) are not at random, but some directions in space are avoided. It is attempted to interpret the phenomena.

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Mit 3 Abbildungen     

Zur Stereochemie der Geruchswahrnehmung von 1-Dekalon-Derivaten und ihren oxaanalogen Verbindungen

Stereochemistry-odor relationships in the 1-decalone series and their oxa-analogs. The olfactory relationships of (?)-(9S,10S)-5,5,9-trimethyl-trans-1-decalone ( 2a ), 6 diasterioisomers in the 11-nordriman-9-one series ( 2b - g ), and 20 racemic 2-oxabicyclo[4.4.0]decanes are reported and correlated with the ‘Triaxial Rule of Odor Sensation’. This rule also is applied to the two internal C(13) acetals derived from (±)-dihydro-γ-ionone as well as to two epimeric C(18) ethers in the labdane series. Syntheses are described for most of the compounds examined.     

Die Stereochemie der Irone

The 6 R configuration of (+)-cis-γ-irone [(+)- 4 ] was established by chemical correlation with (—)-camphor. (+)-cis-γ-irone [(+)- 4 ] was converted into (+)-cis-α-irone [(+)- 1 ], (?)-trans-α-irone [(minus;;)- 2 ], and (+)-β-irone [(+)- 3 ], which therefore also have the 6 R configuration. The 2 S configurations of (+)-cis-α-irone [(+)- 1 ] and (+)-trans-α-irone [(+)- 2 ] were determined by comparison of their circular dichroism with that of R-α-ionone [(+)- 5 ]. The 2 S configuration of (+)-cis-γ-irone [(+)- 4 ] was established by chemical correlation with (+)-cis-α-irone [(+)- 1 ].     

Zur Stereochemie der aromatischen Claisen-Umlagerung. Thermische Umlagerung von erythroiden und threoiden ortho-Dienonen

On the Stereochemistry of the Aromatic Claisen Rearrangement. Thermal Rearrangement of erythroid and threoid ortho-Dienones. Erythro- and threo-1-methyl-1-(1′-methyl-2′-propynyl)-2-oxo-1,2-dihydronaph-thalene (erythro- and threo- 6 ) as well as erythro- and threo-2,6-dimethyl-6-(1′-methyl-2′-propynyl)-cyclohexa-2,4-dien-1-one (erythro- and threo- 8 ) were obtained together with the corresponding aromatic ethers 5 and 7 by alkylation of 1-methyl-2-naphthol and 2,6-dimethyl-phenol, respectively in alcoholic potassium hydroxide solution with 1-methyl-2-propynyl p-toluenesulfonate (Scheme 2). The diastereoisomeric dienones 6 and 8 were easily separated by column chromatography on silica gel and its relative configuration at C(1) or C(6) and C(1′) deduced from the chemical shifts in their ¹H-NMR.-spectra (Table 1). Hydrogenation of 6 and 8 using Lindlar catalyst yielded the corresponding erythro- and threo-configurated (1′-methyl-2′-propenyl)-dienones 10 and 13 , respectively (Scheme 3) the thermal rearrangement of which were studied. The following results were obtained: threo- 10 rearranged in benzene at 85–105° preferentially via a chair-like (C) transition state to yield 99,5% (E)- and 0,5% (Z)-(2′-butenyl) 1-methyl-2-naphthyl ether ((E)- and (Z)- 14 ; ΔΔG (C/B) = ?4,0 kcal/mol). On the other hand, erythro- 10 when heated at 105-125° in benzene gave 84,7% (E)- and 15,3% (Z)- 14 , i.e. in this case a boat-like (B) transition state is favoured (G (C/B) = + 1,3 kcal/mol) (Scheme 5 and Table 2). The thermal rearrangement of dienones 13 led to the corresponding ethers 12 as well as p-allyl-phenols 11 . Thus, heating of threo- 13 at 20–42° in cyclohexane resulted in the formation of 2,5% of ether 12 , consisting of 98% of the (E)- and 2% of the (Z)-isomer, and 97,5% of (E)- 11 which contained, at a maximum, 0,5% of the (Z)-isomer, (Scheme 6 and Table 3). This means that both rearrangements occurred with a strong preference of the C transition state (G ( C/B , phenol) = ?3,3 kcal/mol). On the contrary, erythro- 13 when heated at 42–68° in cyclohexane yielded a 3:2 mixture of ether 12 and phenol 11 (Scheme 6). The ethereal part consisted of 88,0% of the (E)- and 12,0% of the (Z)-isomer which again shows that the B geometry predominated in the erythro transition state leading to the ether (G ( C / B )= + 1,3 kcal/mol). In the phenolic part 36–40% of the (E)-isomer and 64–60% of (Z)-isomer were found which means that in the para-Claisen rearrangement of erythro- 13 the C arrangement is only slightly favoured (ΔΔG ( C / B )= ?0,36 kcal/mol).     

Zur Stereochemie der Vitamin D3-Epoxide Röntgenstrukturanalyse einer 5,6-7,8-Diepoxidverbindung

Epoxidation of vitamin D₃ with benzonitrile ¦H₂O₂¦ KHCO₃ (Payne's reagent) yields exclusively the 5,6-mono-oxirane2. Further epoxidation with the same reagent gives the 5,6-7,8-bisepoxide3 a. Its stereochemistry and therefore the stereochemistry of2 was established by single crystal X-ray analysis of thep-Brbenzoate3b. Thereby for the first time a directive effect of a homoallylic hydroxyl group during thePayne-epoxidation was established.

Herrn Prof.Mihailovic (Universität Belgrad) mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Stereoselektive Bildung von Oxaspiropentanen und Spiropentylketonen. Zur Stereochemie der nucleophilen Substitution am Cyclopropan

Stereoselective Formation of Oxaspiropentanes and of Spiropentyl Ketones. On the Stereochemistry of Nucleophilic Substitution at Cyclopropanes In an intramolecular S_N2-type substitution with formation of the spiro[2.2]-pentane skeleton, the highly strained transition state 2 with one three membered ring in an equatorial/equatorial and one in an apical/equatorial position of a pentacoordinated carbon atom ought to be - at least formally - involved. Yet, several examples of such processes are known. With the endo/exo isomeric bromohydrines 4 and 5 and bromoketones 13 and 14 this reaction is now shown to occur with clean inversion of configuration at the cyclopropane carbon atom. Unambiguous configurational assignments are made by X-ray crystal structure determinations of the 7′exo-bromo-benzoate 6 (from the bromohydrine 4 ), of the endo-sulfonate 12 (from oxaspiropentane 7 , formed from 4 ), of the 7exo-bromonorcarane 13 , and of its cyclization product 15 . - A comparison of the qualitatively measured rates of epoxide ring formation from the closely related systems 18 and 20 proves the expected slower substitution at the cyclopropane carbon atom as compared to the open chain analogue.     

Zur Kenntnis der Ammonium-fluoromanganate(III)

Investigation of the system MnF₃–NH₄F–HF–H₂O revealed considerable hydrolysis even in highly acidic media. NH₄MnF₄ with a tetragonal unit cell,a=7.752 (6),c=6.153 (12) Å andZ=4, was isolated together with the already known (NH₄)₂MnF₅ and (NH₄)₃MnF₆. No splittings of the valence modes were observed with hexa- and penta-fluoromanganates, although the deformation of the octahedra was evident. Splitting was characteristic of the tetrafluoro compound. The spectrum of ammonium ion indicated increasing hydrogenbonding in the sequence hexa-, penta-, tetra-fluoromanganate.

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9. Mitt.: Mh. Chem.106, 1333 (1975).     

Zur Identifizierung der Lokalanaesthetica (LA)

Analytical and Bioanalytical Chemistry -     

Zur Stereochemie der thermischen Fragmentierung von Hydrazonderivaten substituierter N-Amino-aziridine. Vorläufige Mitteilung

The thermally induced fragmentations of the hydrazones derived from phenylglyoxal and the diastereomeric 2,3-diphenyl-1-amino-aziridines and 2,3-dimethyl-1-amino-aziridines proceed with high stereospecificity.     

Über die Stereochemie von Zwischenprodukten (Aldolbasen) der Doebner-von Miller-Chinolin-Synthese

In the Doebner-von Miller quinoline synthesis with acetaldehyde or crotonaldehyde two stereoisomeric 4-hydroxy-1, 2, 3, 4-tetrahydroquinaldines are formed as intermediates. The stereochemistry of these compounds differing in the relative positions of the hydroxygroups to the methyl-group can be ascertained by NMR.-spectroscopy. The pK_a-values of stereoisomers are not identical due to the different spacial positions of the HO-groups.     

Zur Kenntnis der Hexafluorocuprate(III)

On Hexafluorocuprates (III) New prepared are: Cs₂LiCuF₆ (green, trigonal isotypic to Cs₂LiGaF₆; a = 621.5, c = 503.3 pm, γ = 120° from CsCuCl₃, CsCl, Li₂CO₃, p_F2 = 1 bar, 350°C, 2w); K₂LiCuF₆ (green, cubic isotypic to K₂NaCrF₆; a = 792.5 pm from KCuCl₃, Li₂CO₃, KCl, p_F2, = 35 bar, 480°C, 3 d); CsRb₂CuF₆ (green, cubic isotypic to inv. K₂NaCrF₆; a =899,6 pm from CsCuCl₃, RbCl, p_F2 = 1 bar, 400°C, 7 d); CsRbKCuF₆ (green, cubic isotypic to K₂NaCuF₆; a = 886.1 pm from KCuCl₃, CsCl, RbCl, p_F2 = 1 bar, 400°C, 7 d); CsCuCuF₆ (black, orthorhombic isotypic to CsNiNiF₆; a = 706.7, b = 727.7, c = 1032.2 pm from CsCuCl₃, CuCl₂ · 2H₂O, p_F2 = 30 bar, 400°C, 20 h); CsBaCuF₆ (green, tetragonal; a = 598.1, c = 864.6 pm from ?BaCuO₂’?, CsCl, p_F2 = 350 bar, 400°C, 7 d). Also prepared: Cs₂RbCuF₆, Cs₂KCuF₆, Cs₂NaCuF₆, Rb₂KCuF₆, Rb₂NaCuF₆, Rb₂LiCuF₆, K₂NaCuF₆, Na₃CuF₆, K₃CuF₆, Rb₃CuF₆, Cs₃CuF₆ and CsZnCuF₆ (parameters see text). The Madelungpart of Lattice Energy, MAPLE are calculated and discussed. All samples are paramagnetic and follow (exception: CsZnCuF₆) the Curie-Weiss-Law.     

Stereochemie der Polymerisation von 2,3-Dideuteromethyloxiran

Ohne Zusammenfassung