Zur intramolekularen nucleophilen Addition von 2,3-Dihydrodipyrrin-1(10H)-onen

Model compound5 was prepared by acid catalyzedintramolecular nucleophilic addition of the alcohol (Z)-4. In comparison to theintermolecular addition productl-2, differences in structure and reactivity could be determined by X-ray crystal structure analysis and¹H-NMR-spectroscopic investigations. The interpretation of these differences are based on the assumption of stereoelectronic advantages in the intermolecular adductl-2. Its methoxy group was found to beperiplanar with respect to the -(NCO)-plane of the lactam unit enabeling efficient delocalization of the amide lone pair to the *-orbital of the C-OMe-bond. The orientation of the corresponding C-O-bond in5 is fixed by the rigid structure of the bicyclic ring system and can be classified assynclinal. Consequentlyl-2 eliminates methanol very easily under acidic or high temperature conditions, whereas5 is a stable compound.In the stereoelectronically favoured adductl-2 n *-delocalization increases elimination reactivity on the one hand and thermodynamic stability on the other hand. Therefore adducts of this kind may be good candidates for biological regulators—a matter of interest with regard to the protein-chromophore interaction in biliproteins.

     

Stereochemie von Metallocenen, 43. Mitt.: Torsionsisomere Biphenyl-tricarbonylchrom-Komplexe: Darstellung,Konformationsanalyse und Kinetik der Interkonversion

Complexation of methyl 3-nitro-2-(o-tolyl)-benzoate (2, ano-trisubstituted biphenyl) with hexacarbonyl chromium gave the isomeric Cr(CO)₃ complexes3 and4 both existing as two torsional isomersa andb, as seen by nmr. For the main product3 the preferred conformations of the two torsional isomersa andb were deduced by the lanthanide induced shift (LIS) technique. The activation energy for the interconversion process could be determined from kinetic measurements and especially from¹H-nmr coalescence temperature of the methylsignals. The barrier of 91±1.5 kJ/mol (21.7±0.3 kcal/mol) in3 reflects the interaction of theo-H-atom of the benzene ring passing the Cr(CO)₃ moiety of the benchrotrene ring during the interconversion.A partial optical resolution of3 was achieved by asymmetric reduction with a chiral lithium-aluminium hydride yielding (+)-3 with [] _D ²⁰ +30° (benzene) and the levorotatory alcohol (–)-7.

42. Mitt.:K. Schlögl undR. Schölm, Mh. Chem.109, 1227 (1978).     

Strukturelle Abwandlungen an partiell silylierten Kohlenhydraten mittels Triphenylphosphan/Azodicarbonsäurediethylester, 4. Mitt.: Transformationen an Mannose und Galaktose

Reaction of methyl -D-galactopyranoside (1) with two equivalents oft-butyldimethylchlorosilane yields methyl 2,6-bis-O-(tBDMSi)--D-galactopyranoside (1 b), methyl 3,6-bis-O-(tBDMSi)--D-galactopyranoside (1 c) and methyl 4,6-bis-O-(tBDMSi)--D-galactopyranoside (1 d). Likewise methyl -D-mannopyranoside (6) affords methyl 2,6-bis-O-(tBDMSi)--D-mannopyranoside (6 d) and methyl 3,6-bis-O-(tBDMSi)--D-mannopyranoside (6 b), which can be isomerised withTPP/DEAD to methyl 4,6-bis-O-(tBDMSi)--D-mannopyranoside (6 f). Methyl 6-O-(tBDMSi)--D-galactopyranoside (1 a) and methyl 6-O-(tBDMSi)--D-mannopyranoside (6 a) can be prepared from1 or6 with one equivalent oft-butyldimethylchlorosilane.Without an external nucleophile the sugar derivatives1 a and1 b react withTPP/DEAD to form the 3,4-carbonato--D-galactopyranosides1 h and1 i and the 3,4-carbonato-2-O-ethoxycarbonyl--D-galactoside (1 j). In contrast to the formation of the compound1 i by means ofTPP/DEAD the reaction of1 a withTPP and Di-t-butyl-azodicarboxylate (DTBAD) yields the 2,3-anhydro--D-taloside (4 b) and only a small amount of1 i. The epoxide4 b can be cleaved withp-nitrobenzoylchloride/pyridine to the 3-chloro-3-deoxy-2,6-di-O-p-nitrobenzoyl--D-idoside (5). Reaction of1 c and1 d withTPP/DEAD yields the 2,3-anhydro--D-gulopyranoside (2), which can be transformed with NaN₃/NH₄Cl to the 2-azido-2-deoxy--D-idopyranoside (3).Likewise6 a and6 d can be converted to the 3,4-anhydro--D-talosides (7 a and7 b). Reaction of7 b or6 d withTPP/DEAD/NH₃ leads to 3,4-anhydro-2-azido-2-deoxy--D-galactopyranoside (8) and 3-azido-3-deoxy--D-altropyranoside (10), resp.The epoxide7 b is opened with NaN₃/NH₄Cl to the 4-azido-4-deoxymannosides (11 a and11 c) and the 3-azido-3-deoxy--D-idopyranoside (12), while the epoxide8 affords the 2,4-di-azido-2,4-dideoxy--D-glucopyranoside (9).Structures were elucidated by¹H-NMR-analysis of the corresponding acetates.

H. H. Brandstetter undE. Zbiral, Helv., im Druck.     

Heterocyclische Verbindungen aus Zuckern,XV: Zur Konfiguration chiraler C-2-substituierter 4-Thiazolidincarbonsäuren. Chiralitätstransfer auf C-3 in 3,4-Dihydro-1H-pyrrolo[1,2-c]thiazolen

Summary 5-Substituted 3,4-dihydro-pyrrolo[1,2-c]thiazole-6,7-dicarboxylic acid esters3 are obtained from 2-substituted-3-acyl-1,3-thiazolidine-4-carboxylic acids,1 in [3+2]-cycloaddition reactions via mesoionic oxazolone (münchnone) intermediates. The chirality at C-4 of the starting carboxylic acids1 is eliminated in the products3, and the chirality at C-3 (C-2 in the starting carboxylic acids1) can thus be determined through chiroptical measurements. Several representatives of the ring system3 have been characterised through¹H- and CD-spectra and the molecular structure of (3S)-3da has been determined by X-ray crystallography.

     

Protoberberine ausReissert-Verbindungen, 4. Mitt. Eine neue Synthese des (±)-Alamaridins und des (±)-epi-Alamaridins

Summary A novel synthesis of 8-methylisoquino[2,1-b][2,7]naphthyridinium salts7 is reported using the intramolecular cyclization of the 1-substituted isoquinolines5 as the key step, which in turn are obtained by alkylation of theReissert compounds1. The salts7 can be reduced by NaBH₄ yielding the 8- and 8-methylstereomers (±)-alamaridine and (±)-epi-alamaridine9c and11c, respectively.

     

Two different crystal and molecular structures for dicarbonyl(η2-cis-cyclooctene)[η6-1,3,5-triethyl-2,4,6-tris-(trimethylsilylmethyl)-benzene]molybdenum(0): a highly crowded but surprisingly stable molecule

Summary Two crystal and molecular structures have been determined for the sterically very crowded molecule dicarbonyl(²-cis-cyclooctene)[⁶-1,3,5-triethyl-2,4,6-tris-(trimethylsilylmethyl)-benzene]-molybdenum(0),3 a und3 b. In structure3 a the crystals are monoclinic, space group P2₁/n, whereas in3 b they are orthorhombic, space group P2₁2₁2₁. In3 a the carbon-carbon double bond of thecis-cyclooctene moiety is almost parallel to the benzene ring plane; in3 b it is inclined at an angle of nearly 15°. In both3 a and3 b the co-ordinatedcis-cyclooctene and arene moieties adopt conformations which are very similar to those calculated to be the ground states of the free molecules.

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Zwei unterschiedliche Kristall- und Molekülstrukturen von Dicarbonyl (²-cis-cycloocten)[⁶-1,3,5-triethyl-2,4,6-tris-(trimethylsilylmethyl)-benzol]molybdän(0): einem hochgespannten aber überraschend stabilen Molekül

Zusammenfassung Von dem sterisch sehr gespannten Molekül Diarbonyl(²-cis-cycloocten)[⁶-1,3,5-triethyl-2,4,6-tris-(trimethylsilylmethyl)-benzol]molybdän(0) wurden zwei unterschiedliche Kristall-und Molekülstrukturen3 a und3 b ermittelt. Die Kristalle von3 a sind monoklin (Raumgruppe P2₁/n), jene von3 b orthorhombisch (Raumgruppe P2₁2₁2₁). In3 a ist die Kohlenstoff-Kohlenstoff Doppelbindung dercis-Cycloocteneinheit nahezu parallel zum Benzolring angeordnet; in3 b ist sie um etwa 15° gekippt. Die Konformationen des koordiniertencis-Cycloocten sowie des Arens sind sehr ähnlich jenen Grundzustandsstrukturen, die für die nichtkoordinierten Moleküle berechnet wurden.

     

Zur Kenntnis organischerLewis-Säuren, 36.Cis—trans-Gleichgewichte und Konformationen von 2,(x)-Dialkyl-1-dicyanomethylencyclohexanen. Wahlweise einfache Darstellung dercis- odertrans-Formen

Knoevenagel condensation of malononitrile withcis- andtrans-2,5-dimethylcyclohexanone (1 c and1 t, respectively) leads to2 c and2 t, respectively, and withtrans-1-decalone to4 t. The equilibria2 c2 t and4 c4 t have been determined as well as, by means of 270-MHz-¹H-NMR, the conformations of these four compounds. The dicyanomethylene group is found to induce axial positions of neighbouring alkyl residues on the cyclohexane ring (or when this is impossible, as in the case of4 t, the twist form of the cyclohexane ring). This results in a strong predominance of thecis isomers in the equilibria2 c2 t and4 c4 t whereas thetrans isomers strongly predominate in the equilibria among the starting ketones. This situation allows the optional preparation of2 c or2 t, and of4 c or4 t, from the more stable starting ketone (or ketone mixture). The free conformational energy of the distorted twist form of4 t amounts to 17 kJ/mol.

Herrn Prof. Dr.E. Ziegler, Graz, zum 70. Geburtstag in aufrichtiger Verbundenheit gewidmet.     

NMR-spektroskopische Untersuchungen zurE/Z-Isomerie von substituierten Dithiocarbazinsäurederivaten

Summary NMR-spectroscopic investigations of substituted dithiocarbacinic acid derivatives show the existence of configurational isomers relative to the C=N double bond, but no tautomerism. We applied chemical shift differences in the¹H-,¹³C- and¹⁵N-NMR-spectra, N - H and C - H coupling constants and NOE difference measurements in the solvents CDCl₃,DMSO-d ₆ and partly CD₃OD in order to discriminate between the isomers and to determine the configurational composition. Compounds4 and5 exist asE-isomers in all solvents, compounds1, 2 and3 as a mixture ofE/Z-isomers. InDMSO-d ₆ theE-form is the preferred isomer.

     

Synthesis in the isocamphane series,XVI. The regioselectivity of some lewis acids in the catalyzed Diels-Alder-reaction of cyclopentadiene and mesityloxide

Zusammenfassung The regioselectivity of 9Lewis acids in the catalyzedDiels-Alder-reaction of cyclopentadiene and mesityloxide is described and theendo: exo-ratio of1 a and1 b determined by quantitative HPLC- and¹H-NMR-measurements. The reaction mixture of1 a+1 b normally contains more of theendo epimer1 a, e.g. 31 for1 a1 b, and is therefore in agreement with theendo rule, only TiCl₄ favors theexo epimer1 b.

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Synthesis in the isocamphane series, XVI. The regioselectivity of some lewis acids in the catalyzed Diels-Alder-reaction of cyclopentadiene and mesityloxideShort communication

Teil der Diplomarbeit vonHuber, U., Universität Wien, 1980.     

NMR studies of 4(3H)-quinazolinones and 4(3H)-quinazolinethiones

Summary Unambiguous¹H and¹³C NMR assignments for 4(3H)-quinazolinones1–6 and their corresponding 4-thiones7–12 have been made. This resulted in the revision of the previous assignments for the two benzenoid carbons (C-5 and C-8) of quinazolinones1,2,4, and5. Thionation of the nucleophilic amides1–6 has been found to cause a distinct change in the¹³C chemical shift of particularly C-4, but also of those of C-4a, C-5, and C-8a. One-bond and several long range heteronuclear coupling constants for the compounds have also been measured.

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Kernresonanzspektroskopie von 4(3H)-Chinazolinonen und 4(3H)-Chinazolinthionen

Zusammenfassung Die¹H- und¹³C-NMR-Spektren der 4(3H)-Chinazolinone1–6 und ihrer entsprechenden 4-Thione7–12 wurden zugeordnet. Dabei zeigte sich, daß eine frühere Zuordnung der beiden benzoiden Kohlenstoffe (C-5 und C-8) der Chinazolinone1,2,4 und5 falsch war. Ersatz des Sauerstoffs durch Schwefel in den nukleophilen Amiden1–6 führt insbesondere für C-4, aber auch für C-4a, C-5 und C-8a zu einer deutlichen Änderung der chemischen Verschiebung. Heteronukleare Kopplungskonstanten über eine und über mehrere Bindungen wurden bestimmt.

     

Synthesen von 4-Amino-thieno[2,3—b]pyridinen

The Cyclization of 2-(1,1-dicyanovinylamino)-thiophenes2 by treatment with AlCl₃ yield 4-amino-5-cyano-thieno[2,3-b]pyridines3. 2-(1-acylvinyl-amino)-3-cyano-thiophenes7, obtainable from 2-amino-3-cyano-thiophenes and -diketones, react in the presence of AlCl₃ to form 4-acylamino-thieno[2,3-b] pyridines8. This reaction is connected with the transfer of the acyl group from C- to the N-atom. 4-Amino-5-cyano-thieno[2,3-b]pyridones-(6)11 are synthesized from 2-amino-3-cyano-thiophenes and ethyl cyano acetate in the presence of sodium ethoxide.

     

Über die Darstellung der 7R-Oxirane von 5Z- und 5E-10-Oxo-19-norcholecalciferol

Summary The two title compounds12b and13b have been prepared by direct oxidation of the corresponding 10-oxo-19-norcolcalciferol derivatives3c and4c withMCPBA. The generation of12b and13b by treatment of the ⁷ epoxidized ethylisoxazolin adducts of 5Z- and 5E-cholecalciferol8a,8b and9a,9b with Mo(CO)₆ failed, since besides the retroaldol cleavage of the heterocycle a deoxygenation of the oxirane with retention of configuration to the ⁷ double bond occurs.

     

Zur Chemie der vicinalen Triketone,XII Versuche zur Darstellung vonSchiffschen Basen aus cyclischen,vicinalen Triketonen

The quinolinetrionesTMCH, PCH, MCH and phenalene trione (PT) do not react with aryl isocyanates toSchiff bases^5a, but react by ring contraction to yield the spiro-imidazolidines2 a-d,3 a-e,4 a-b and5 a-cbd. However, reaction of ninhydrine with aryl isocyanates gives the 1:2 adductes1 a-e. Benzal aniline reacts withTMCH, PCH. andPT to yield known phenoxazine derivatives^2c,11. In contrast,PCH orMCH react with benzylidene benzalaniline to yield theSchiff bases7 a-b. which can be transformed into the bisamine8. comparable to the ninhydrine reaction.

Herrn emer. o. Univ. Prof. Dr.Erich Ziegler, Graz, mit besten Wünschen zur Vollendung des 70. Lebensjahres gewidmet.     

Stereochemistry of planarchiral compounds,XIV. Static and dynamic stereochemistry of 3,3′-dimethoxy-2,2′-bi(1,6-methano[10]annulenyl)

Summary The title compound6 was prepared from 3-methoxy-1,6-methano[10]annulene (4)via lithiation and oxidative coupling of the intermediate5 with copper(II)chloride. Three stereoisomers (two rotamers of the racemate,6a and6b, and themeso-form6c) were obtained and their configurations assigned both by¹H NMR spectroscopy and by X-ray crystal structure analysis of6a.Starting the reaction sequence from optically active 2-bromo-1,6-methano[10]annulene, (–)-3, of known absolute chirality (S)_p established the absolute stereochemistry of (+)-6a as (R)_p(R)_a(R)_p and (R)_p(S)_a(R)_p for the dextrorotatory rotamer6b. 3-Methoxy-1,6-methanol[10]annulene (4) as well as6a and6b were easily resolved by enantioselective chromatography of the racemic mixtures on cellulose triacetate (CTA) in ethanol. A rotational barrier of G ^#=132 kJ·mol^–1 between6a and6b was determined both by thermal equilibration and by CD-kinetics.Finally, also themeso-form6c — because of its high rotational barrier (118 kJ) — could be resolved onCTA in its enantiomers ([]_D=200° in ethanol). From chiroptical comparison (CD) with6a and6b, resp., the chirality (R)_p(S)_a(S)_p was deduced for (+)-6c.

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Stereochemie planarchiraler Verbindungen, 14. Mitt. Statische und dynamische Stereochemie von 3,3-Dimethoxy-2,2-bi(1,6-methano[10]annulenyl)

Zusammenfassung Die Titelverbindung6 wurde aus 3-Methoxy-1,6-methano[10]annulen (4) durch Lithiierung und anschließende oxidative Kupplung des Zwischenproduktes5 mit Kupfer(II)chlorid erhalten. Dabei entstanden3 Stereoisomere (2 Rotamere des Racemates,6a und6b, und diemeso-Form6c), deren Konfiguration sowohl durch¹H-NMR-Spektroskopie als auch durch Röntgenstrukturanalyse von6a bestimmt wurden.Ausgehend von optisch aktivem 2-Brom-1,6-methano[10]annulen, (–)-3, bekannter Absolutkonfiguration (S)_p, konnte durch diese Reaktionsfolge die absolute Chiralität von (+)-6a als (R)_p(R)_a(R)_p [und (R)_p(S)_a(R)_p für (+)-6b] ermittelt werden. Sowohl4 als auch6a und6b waren durch enantioselektive Chromatographie an Cellulose triacetat (CTA) in Ethanol glatt in ihre Enantiomeren trennbar. Die Rotationsbarriere zwischen6a und6b wurde sowohl durch thermische Äquilibrierung als auch CD-Kinetik zu G ^#=132 kJ·mol^–1 bestimmt.Schließlich ließ sich auch die Mesoform6c wegen ihrer hohen Rotationsbarriere von 118 kJ·mol^–1 anCTA glatt in ihre Enantiomeren trennen ([]_D=200° in Ethanol). Aus einem chiroptischen Vergleich mit6a bzw.6b (CD) wurde für (+)-6c die Chiralität (R)_p(S)_a(S)_p abgeleitet.

     

Strukturelle Abwandlungen anN-Acetylneuraminsäure, 3

From methyl-5-acetylamino-7,8-anhydro-4,9-O-bis-(t-butyldimethylsilyl)-3,5-dideoxy--D-glycero-D-galacto-2-nonulopyranosidonic acid methylester (1) the derivatives1 a and1 b were obtained by removing the 9-O-(t-butyldimethylsilyl)group withBu ₄NF, followed by acetylation. Treatment of1 b with 80% acetic acid and acetanhydride/pyridine yields the 8-epi-N-acetylneuraminic acid derivative2 a and the 7-epi-N-acetylneuraminic acid derivative3 a in a ratio of 3:1 (Scheme 1). The structure elucidation of2 b was achieved by converting2 b via the 4,9-bis-O-(tBDMSi)-8-O-tosyl-derivative2 d into the epoxide1 (Scheme 2). Using the same sequence the epoxides4 and5 were transformed into theN-acetylneuraminic acid derivative6 a and the 7,8-bis-epi-N-acetylneuraminic acid derivative7 a (Scheme 3). After treatment with sodium hydroxide and 0.025m HCl and Dowex 50 H⁺ the 8-epi-, 7-epi- and 7,8-bis-epi-N-acetylneuraminic acids2,3, and7 were obtained. These three compounds were tested withCMP-N-acetylneuraminic acid synthetase.

Herrn KollegenK. Schlögl mit den besten Wünschen zum 60. Geburtstag.     

Reaction of 3-phenyl-5-aminopyrazole with carbon disulfide: A novel synthesis of 3-(3′-phenylpyrazol-5′-yl)-4-phenylpyrazol-2-thione as well as of pyrazolo[3,4-d]thiazole and pyrano[2,3-d]thiazole derivatives

Summary 3-Phenyl-5-aminopyrazole (1) reacts with carbon disulfide, followed byin situ reaction with -haloketones3a–c, to afford5,7a, and7b, respectively. Compounds5 and7 were further utilized for the formation of heterocycles and their fused derivatives.

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Reaktion von 3-Phenyl-5-aminopyrazol mit Schwefelkohlenstoff: Ein neue Synthese von 3-(3-Phenylpyrazol-5-yl)-4-phenylprazol-2-thion sowie von Pyrazolo[3,4-d]thiazol- und Pyrano[2,3-d]thiazolderivaten

Zusammenfassung 3-Phenyl-5-aminopyrazol (1) reagiert mit Schwefelkohlenstoff und anschließendin situ mit den -Halogenketonen3a–c zu5,7a und7b. Die Verbindungen5 und7 wurden weiter zu Heterocyclen und ihren kondensierten Derivaten umgesetzt.

     

New syntheses of 2,4-diaminopyrroles and aminopyrrolinones

Summary Oxazolin-2-ylidene-malononitriles3a–d, obtainable from thioketenaminals and -halogen-ketones, react with primary and secondary amines to afford 2,4-diamino-pyrroles5a–h. Mercaptobenzen as nucleophilic agent gives the 4-amino-2-phenylthio-pyrrole5j. Analogously, cyano-(3,5-diphenyl-3H-oxazol-2-ylidene)-acetic acid methyl esters were prepared as intermediates for the synthesis of 2-amino-4-oxo-pyrrolines10a–d. The isomeric 4-amino-2-oxo-pyrrolines13a–d can be obtained from 4-amino-2-methoxy-pyrroles, which serves as proof for the position of substituents. The structures were investigated by¹H and¹³C NMR spectroscopy.

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Neue Synthesen von 2,4-Diaminopyrrolen und Aminopyrrolinonen

Zusammenfassung Die Oxazolin-2-yliden-malononitrile3a–d. die aus Thioketenaminalen und -Halogenketonen erhalten wurden, reagieren mit primären und sekundären Aminen zu den 2,4-Diaminopyrrolen5a–h. Mercaptobenzol als nukleophiles Reagens liefert 4-Amino-2-phenylthiopyrrol (5j). Analog wurden Cyan-(3,5-diphenyl-3H-oxazol-2-yliden)-essigsäuremethylester als Zwischenprodukte für die Synthese der 2-Amino-4-oxo-pyrroline10a–d hergestellt. Die isomeren 4-Amino-2-oxo-pyrroline13a–d können aus den 4-Amino-2-methoxy-pyrrolen11a,b erhalten werden, was als Nachweis für die Position der Substituenten dient. Die Verbindungen wurden¹H- und¹³C NMR-spektroskopisch untersucht.

     

Umsetzung von Metall- und Metalloidverbindungen mit mehrfunktionellen Molekülen, 31. Mitteilung

The reaction of galliumtrichloride and galliumtribomide resp. with 2,6-dimethyl- and 2,4,6-trimethyl-N-trimethylsilyl-trifluoroacetanilide leads to the trifluoracetanilidodihalogenogallanes1–3. The 2,6,9-trioxa-4,8-diaza-1,5-digalla-bicyclo-[3.3.1]-nonadiene derivatives1 a–3 a are formed probably as by products.N-Trimethylsilyltrifluoroacetamide reacts with galliumtrichloride to yield the trifluoroacetamido-dichlorogallane4.N-Trimethylsilyl-N,N,N-triorganyl-thioureas react with galliumtrichloride under elimination of chlorotrimethylsilane to give the thio-ureido-gallanes5 and6. IfN,N-diorganylureas andN,N-diorganyl-thio-ureas resp. are reacted with galliumtrichloride and methyl-gallium-dichloride resp., the thio-ureido- and ureido-gallanes7–9 are obtained by elimination of hydrogenchloride. The compounds are characterized by analysis and spectral data (NMR:¹H,¹⁹F; MS; IR). The substances are monomeric in the gas phase, obviously due to internal coordination.

30. Mitt.:W. Maringgele undA. Meller, J. Organomet. Chem., im Druck.     

Zum Verhalten von Orthocarbonsäureestern gegenüber Trimethylsilylchlorid, -azid und -cyanid

The reaction of cyclic orthoesters of cyclohexanes and steroides with trimethylsilylchloride,-azide and-cyanide points out novel, mechanistic aspects as well as remarkable preparative possibilities. The mixture1 a/1 b of theexo/endo stereoisomers of the cyclic orthoesters derived fromcis-cyclohexane-1,2-diol was transformed to the expected 1-yl-ethanoate3 of thetrans-2-chlorocyclohexan-1-ol. In contrast the reaction of1 a/1 b with trimethylsilylazide and trimethylsilycyanide yields the correspondingexo/endo mixtures of2 a/2 b and2 c/2 d resp. The cyclic orthoester oftrans-cyclohexan-1,2-diol (4) similarily affords the products5 a and5 b, whereas transformation with trimethylsilylchloride 1-yl-ethanoate of thecis-2-chlorocyclohexan-1-ol could not be achieved for steric reasons. The cyclic orthoesters6 a/6 b ofcis-cyclohex-1-en-3,4-diol are converted regio- and stereospecifically to the products7 and9 using trimethylsilychloride and- azide, whereas theexo/endo mixture8 a/8 b of the corresponding cyclic orthoester derivative is formed with trimethylsilylcyanide. The orthoesters10 a/10 b prepared from 2,3-cis-dihydroxycyclohexanone-1 give thetrans-2-chloro-3-oxocyclohexyl-ethanoate (11) and its elimination product12. In analogy13 is produced by treating10 a/10 b with trimethylsilylacetate. Theexo/endo mixture of cyclic esters14 a/14 b 3-cholestan-2,3-diol gives the corresponding mixture15 a/15 b when treated with trimethylsilycyanide. Reaction of Trimethylsilychloride with14 a/14 b affords mainly thetrans-diequatorial product17 a and only small amounts of thetrans-diaxial product17b. In contrast the mixture18a/18b yields exclusively thetrans-diaxials product20 on reaction with trimethylsilylchloride. With trimethylsilcyanide the cyclic orthoester derivative21 a/21 b is formed. The cyclic esters22 a/22 b of 1,2-dihydroxychloestanone-3 react with trimethylsilylchloride to give the easily explicable elimination product23 and the rearranged 3-methoxy-cholesten-3-one-2 (24). The corresponding cyclic orthesters25 a/25 b of 1,2-dihydroxy-3-oxo-androstans-17-yl-ethanoate in a similar way afford the elimination product26 to a small extent and the rearranged 3-methoxy-2-oxo-androstan-17-yl-ethanoate (27) as the main product.

Herrn Prof. Dr.H. Pommer mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Tetracyclische Imidazole

2-(Phenacyl)-tetrahydro--carboline (2) was transformed to theE/Z-oximes3 and4 and the isolated species cyclodehydrogenated to the nitrone5 and oxadiazine6. These compounds were dehydrated in acidic medium to the imidazole9.