Untersuchungen über die Bildung von 2-Acylcyclopentanonen aus 1-(1-Äthynyl)-cyclopentenen und Perameisensäure

The reaction of1 a with H₂O₂ in HCOOH yielded 37%4 a and 15%3 a. 1 c reacted under similar conditions to4 c (29%),3 b (12%) and3 c (22%).1 b was less reactive towards H₂O₂ in HCOOH due to its low solubility in HCOOH;4 b was isolated with 6% yield, 69%1 b remained unchanged.Under conditions of epoxide hydrolysis and catalysis of theRupe rearrangement, the epoxides2 a and2 b yielded 37%4 a and 30%4 b, resp.Based upon these experimental results, mechanisms for the observed reactions are proposed.     

Bicyclic N-heterocyclic carbene (NHC) ligand precursors and their palladium complexes

Eight bicyclic amidinium precursors (3), prepared from R,S-tmcp (R,S-tmcp: (1R,3S)-diamino-1,2,2-trimethylcyclopentane) were described. Only five of the precursors (3a–e) could be converted to palladium complexes, (PdX₂(6,7-NHC)PEPPSI) (4) by treatment with PdCl₂, K₂CO₃, and pyridine (additional KBr was used for (PdBr₂(6,7-NHC)PEPPSI)). The salts and complexes were fully characterized by spectroscopic methods and X-ray crystallography.     

2′,3′‐Dehydrosalannol

The title compound, methyl (2aS,3R,5R,5aS,6S,6aS,8R,9aS,10aR,10bR,10cS)‐8‐(3‐furyl)‐2a,4,5,5a,6,6a,8,9,9a,10a,10b,10c‐dodeca­hydro‐3‐hydroxy‐2a,5a,6a,7‐tetra­methyl‐5‐(3‐methylbut‐2‐enoyl­oxy)‐2H,3H‐cyclo­penta­[4′,5′]­furo­[2′,3′:6,5]benzo[cd]­isobenzo­furan‐6‐acetate, C₃₂H₄₂O₈, was isolated from uncrushed green leaves of Azadirachta indica A. Juss (neem) and has been found to possess antifeedant activity against Spodptera litura. The conformations of the functional groups are similar to those of 3‐des­acetyl­salannin, which was isolated from neem kernels. The mol­ecules are linked into chains by intermolecular O—H?O hydrogen bonds.     

Asymmetric Allylic Substitution Reactions with a Xylophos-Pd Catalyst

Summary.  The chiral diphosphine ligand xylophos (1) was tested as an auxiliary in palladium catalyzed allylic substitution reactions. Whereas its activity was found to be generally good only in the case of 1,3-diphenylprop-2-en-1-yl acetate, a fair level of asymmetric induction was achieved with sodium dimethyl malonate (83%ee) and benzylamine (66%ee) as nucleophiles. Received June 13, 2000. Accepted July 3, 2000     

Total synthesis of (3Z,9Z,6S,7R) and (3Z,9Z,6R,7S)-6,7-epoxy-3,9-octadecadienes

(3Z,9Z,6S,7R)-6,7-epoxy-3,9-octadecadiene (1) and (3Z,9Z,6R,7S)-6,7-epoxy-3,9-octadecadiene (2) have been stereoselectively synthesized in eight steps from 2-pentyn-1-ol with an overall yield of 8%. The key steps involved the Sharpless asymmetric dihydroxylation of (2E)-oct-2-en-5-yn-1-ol (6). The new synthetic method is suitable for multigram-scale preparation of 1 and 2 and might be used for producing sufficient quantities of the sex pheromone components for management of the pest of tea plantations.     

Asymmetric Allylic Substitution Reactions with a Xylophos-Pd Catalyst

 The chiral diphosphine ligand xylophos (1) was tested as an auxiliary in palladium catalyzed allylic substitution reactions. Whereas its activity was found to be generally good only in the case of 1,3-diphenylprop-2-en-1-yl acetate, a fair level of asymmetric induction was achieved with sodium dimethyl malonate (83%ee) and benzylamine (66%ee) as nucleophiles.     

Synthese von 1-Ary1-4-methylthio-2-azetidinonen

TheN-arylthioformimidates4 a-e, which may be obtained byS-alkylation of the thioformanilides3 a-e, react with chloroacetylchloride/triethylamine to yield the (3R,4S/3S,4R)-1-aryl-3-chloro-4-methylthio-2-azetidinones5 a-e and the formanilides6 a-e. Dehalogenation of5 b-e with tri-n-butyltinhydride yield the title compounds7 b-e. Hydrogenolysis of7 b and7 c yields7 f and7 g.

     

Die katalytische Hydrierung von 14-Brom-codeinon-dimethylacetal

Zusammenfassung Die katalytische Hydrierung von 14-Brom-codeinondimethylacetal (2a) liefert in erster Linie die drei dimeren Neopinon-acetale (bd6,7) und8, sowie Neopinon-dimethylacetal (3b), Dihydro-codeinon-dimethylacetal (9) und (7R)-7-Hydroxyneopinon-dimethylacetal (10). Die Ausbeuten an Dimeren nehmen bei Vergrößerung des Reaktionsvolumens ab. Bei einer besonderen Ausführung der Hydrierung ist9 in 87proz. Ausbeute zugänglich. Die Strukturen und die Konfiguration an C-7 von6,7,8 und3b werden bewiesen und einige Umwandlungsprodukte beschrieben.

---

The catalytic hydrogenation of 14-bromo-codeinone dimethyl acetal

The palladium-catalyzed hydrogenation of2a mainly leads to the new dimeric compounds6,7 and8, beside3b,9, and10. The yield of dimeric compounds is decreased by increasing the volume of the solvent. Under certain conditions9 in 87% yield is formed. The structures and the configuration on C-7 of3b,6,7, and8 are also derived.

---

---

Unserem verehrten Lehrer, Herrn Prof. Dr.F. Vieböck, mit den besten Wünschen zum 70. Geburtstag gewidmet.

---

Aus der DissertationH. Markut, Univ. Wien 1971.     

The first example of asymmetric Michael reaction catalyzed by chiral alkali metal alkoxides

Some chiral sodium alkoxides can be used as catalysts in the asymmetric Michael reaction as exemplified by the 1,4-addition of an achiral Ni^II complex of the Schiff base derived from glycine andN-(2-pyridylcarbonyl)-o-aminobenzophenone (1) to methyl methacrylate (2) or methyl acrylate (14). The products of the reaction of1 with2,viz., the corresponding diastereomeric complexes of 4-methylglutamic acid, are formed in dissimilar amounts (de 26–85%); theee value for the major diastereomer (2S,4R)-3a is 28%. After recrystallization, the enantiomeric purity of complex3a increases toee>85%. Acidcatalyzed hydrolysis of the enantiomerically enriched complex3a affords (2S,4R)-4-methylglutamic acid (ee>85%). The complex of glutamic acid15 resulting from the reaction of1 with14 is formed with anee of 45%. After recrystallization, the enantiomeric purities of complex15 and glutamic acid increase toee>90%.     

Synthesis of methyl-α-<Emphasis Type="SmallCaps">d</Emphasis>-glucopyranoside-based azacrown ethers and their application in enantioselective reactions

New chiral monoaza-15-crown-5 compounds anellated to methyl-4,6-O-(1-naphthyl)methylene-α-d-glucopyranoside (2a–2b), to methyl-4,6-O-isopropylidene-α-d-glucopyranoside (3a–3b) and to methyl-α-d-glucopyranoside (4a–4b) have been synthesized. Several representatives of these crown ethers showed significant asymmetric induction as chiral phase transfer catalysts, among them 2a proved to be the most efficient one inducing 90% ee in the Michael addition of 2-nitropropane to chalcone, 48% ee in the Darzens condensation of phenacyl-chloride with benzaldehyde and 89% ee in the epoxidation of chalcone with tert-butyl hydroperoxide. The catalytic results were compared with those obtained earlier with macrocycles 1a–1b incorporating a 4,6-O- benzylidene protecting moiety. It occurred that the enantioselectivity is influenced to a great extent by the substituents on the C(4) and C(6) atoms of the monosaccharide. Lower enantioselectivities were obtained in the reactions of the chalcone analogues in the presence of catalyst 2a than in the case of the proper chalcone. Correspondence: Péter Bakó, Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, 1521 Budapest, P.O. Box 91, Hungary.     

Synthesis of novel crown ethers. Part 1. Coumestan and coumestan analog derivatives of crown ethers

The presented ethylenedioxy compounds5a,5d,6a and6c are examples of novel cyclic ethers, while macrocyclic polyethers represent new crown ether analogues. New coumestan-crowns5a-f, derivatives of 6,7-dihydroxy-3,4-dihydro-2H-dibenzofuran-1-one and 6,7-dihydroxy-3,3-dimethyl-3,4-dihydro-2H-dibenzofuran-1-one6a-e were synthesized from the correspondingo-dihydroxy compounds3a-b,4a-b and ditosylates or dichlorides of di- or triethylene glycol in the presence of K₂CO₃, in DMF/H₂O (15/1) solutions at 65–75 °C for 35 hours. The structure of the macrocyclic ethers obtained were confirmed by¹H-NMR,¹³C-NMR, IR spectra and elemental analyses.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Synthese des 4-Hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thions bzw. -ons und der entsprechenden Tautomeren

The tautomers 4-hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione (4 a) and 2-mercapto-6,6-dimethyl-5,6-dihydro-4H-thiopyran-4-one (4 b) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-2H-thiopyranthiones6,8. On methylation of4 a,b only the S-methyl product7 is formed. Hydrolysis of 4-amino-2-methylthiothiopyranyliden iodides11 leads—depending on the amino group of11—either to the thiopyranone7 or to the 4-imino-thiopyranes12 and to -amino-,,,-unsaturated-methyldithio carboxylates13. On reaction of4 a,b with hydrogenperoxyd the tautomers 4-hydroxy-5,6-dihydro-2H-thiopyran-2-one5 a and 5,6-dihydro-2H-thiopyran-2,4(3H)diones5 b resp. are formed.4 a,b and5 a,b undergo an aminolysis with prim. and sec. amines to the corresponding 4-amino-2H-thiopyran-2-thiones6,8 and -ones10 resp. On heating in alcohols the 4-alkoxy-thiopyrane-2-thiones and -ones9,14 are formed from4 a,b and5 a,b resp.

     

Halo-substituted (S)-N-(2-benzoylphenyl)-1-benzylpyrolidine-2-carboxamides as new chiral auxiliaries for the asymmetric synthesis of (S)-α-amino acids

The synthesis of new chiral auxiliaries (S)-N-(2-benzoylphenyl)-1-(3,4-dichlorobenzyl)-pyrrolidine-2-carboxamide (1a), (S)-N-(2-benzoylphenyl)-1-(pentafluorobenzyl)pyrrolidine-2-carboxamide (1b), and (S)-N-(2-benzoylphenyl)-1-(4-isopropoxytetrafluorobenzyl)pyrrolidine-2-carboxamide (1c) and their application in the asymmetric synthesis of amino acids using Ni^II complexes of their Schiff"s bases with alanine and glycine are described. Compound 1a is particularly appropriate for highly stereoselective synthesis of -methyl--amino acids with high enatiomeric purity (ee >95%).     

Synthesis of methyl-α-d-glucopyranoside-based azacrown ethers and their application in enantioselective reactions

New chiral monoaza-15-crown-5 compounds anellated to methyl-4,6-O-(1-naphthyl)methylene-α-d-glucopyranoside (2a–2b), to methyl-4,6-O-isopropylidene-α-d-glucopyranoside (3a–3b) and to methyl-α-d-glucopyranoside (4a–4b) have been synthesized. Several representatives of these crown ethers showed significant asymmetric induction as chiral phase transfer catalysts, among them 2a proved to be the most efficient one inducing 90% ee in the Michael addition of 2-nitropropane to chalcone, 48% ee in the Darzens condensation of phenacyl-chloride with benzaldehyde and 89% ee in the epoxidation of chalcone with tert-butyl hydroperoxide. The catalytic results were compared with those obtained earlier with macrocycles 1a–1b incorporating a 4,6-O- benzylidene protecting moiety. It occurred that the enantioselectivity is influenced to a great extent by the substituents on the C(4) and C(6) atoms of the monosaccharide. Lower enantioselectivities were obtained in the reactions of the chalcone analogues in the presence of catalyst 2a than in the case of the proper chalcone.     

Total Synthesis of (+)‐Gracilamine Based on an Oxidative Phenolic Coupling Reaction and Determination of Its Absolute Configuration

The enantioselective total synthesis of (+)‐gracilamine ( 1 ) is described. The strategy features a diastereoselective phenolic coupling reaction followed by a regioselective intramolecular aza‐Michael reaction to construct the ABCE ring system. The configuration at C3a in 1 was controlled by the stereocenter at C9a, which was selectively generated (91 % ee) by an organocatalytic enantioselective aza‐Friedel–Crafts reaction developed by our research group. This synthesis revealed that the absolute configuration of (+)‐gracilamine is 3aR, 4S, 5S, 6R, 7aS, 8R, 9aS.     

On the Effect of Diene Geometry in Intramolecular Allyl Cation Cycloadditions

Attempted intramolecular allyl cation cycloaddition of trienol 2a, which contains a conjugated diene of Z-configuration, affords monocyclic trienes 3a,b, in contrast to related trienols known to produce [5,5]-bicyclic and/or [5,7]-bicyclic products. Cyclopentyl trienes 3a,b are isomeric with multifidene, an algal pheromone. Dimethyl trienol 6 fails to cyclize (under identical conditions), but eliminates to yield tetraene 7.     

Catalytic enantioselective addition of diethylzinc to (hetero)aromatic aldehydes

The asymmetric alkylation with diethylzinc of five heterocyclic aldehydes and benzaldehyde (for comparison) has been studied in the presence of two optically active amino alcohols: (S)-2-amino-1-butanol (AB) and (1S,2R)-N,N-dibutylnorephedrine (DBNE). A number of chiral (hetero)aromatic secondary alcohols were synthesized in high yields (95–98%) with enantioselectivity up to 92% enantiomeric excess (ee) in the presence of DBNE catalyst. Optically active thienyl and 4-pyridyl derivatives were prepared for the first time by catalytic asymmetric alkylation. The influence of the amount of DBNE on the enantioselectivity was investigated. In contrast to benzaldehyde, 2-furan- and 2-thiophene-carbaldehydes, in the case of 3- and 4-pyridinecarbaldehydes the ee values depend directly on the catalyst concentration. © 1998 John Wiley & Sons, Ltd.     

Biphenyl-tricarbonylchrom-komplexe, 9. Mitt.: Synthesen,chromatographische Enantiomerentrennung,Circulardichroismus und Chiralität von mono- und bis-(Tricarbonylchrom)-Komplexen di- und tetrasubstituierter sowie überbrückter Biphenyle

Chiral title compounds have been resolved by medium pressure liquid chromatography (MPLC) on triacetylcellulose in ethanol. Whereas a quantitative separation was achieved for16 and20, a recycling technique had to be applied to1,4,6,10 and15 leading to a 100% e.e. for1,6 and15 and to ca. 60% e.e. for4 and10.An unambiguous assignment of the chirality (+)-(R) _a -(S) _m for tricarbonylchromium-6,6-dimethyl-diphenicacid dimethylester (4) was deduced both from the photochemical decomplexation to (-)-5 with the known chirality (R) _a (whose e.e. was determined by MPLC on triacetylcellulose) and by comparison of the¹H-n.m.r. spectra of4 and5 thereby proving the structure 4 for the former.Other chiralities both for mono and bis(tricarbonylchromium)biphenyl complexes were established by chemical correlations and comparison of the CD spectra with those of key compounds.

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

NOVEL 2-THIOXOHYDANTOIN KETENE DITHIOACETALS: VERSATILE INTERMEDIATES FOR SYNTHESIS OF METHYLSULFANYLIMIDAZO- [4,5-C]PYRAZOLES AND METHYLSULFANYLPYRROLO- [1,2-C]IMIDAZOLES

ABSTRACT

The novel 2-thioxohydantoin ketene S,S-acetals 3a,b were prepared by the reaction of 2-thioxohydantoins 1a,b with carbon disulfide, followed by alkylation with methyl iodide of the produced sodium dithiolate salts 2a,b. The reaction of compounds 3a,b with nucleophiles afforded different fused methylsulfanylimidazoles.     

Enantioselective Synthesis and Application to the Allylic Imidate Rearrangement of Amine‐Coordinated Palladacycle Catalysts of Cobalt Sandwich Complexes

The reaction of (η⁵‐(N,N‐dimethylaminomethyl)cyclopentadien‐yl)(η⁴‐tetraphenylcyclobutadiene)cobalt with sodium tetrachloropalladate and (R)‐N‐acetylphenylalanine gave planar chiral palladacycle di‐μ‐chloridebis[(η⁵‐(S_p)‐2‐(N,N‐dimethylaminomethyl)cyclopentadienyl,1‐C,3′‐N)(η⁴‐tetraphenylcyclobutadiene)cobalt]dipalladium [(S_p)‐Me₂‐CAP‐Cl] in 92 % ee and 64 % yield. Enantiopurity (>98 % ee) was achieved by purification of the monomeric (R)‐proline adducts and conversion back to the chloride dimer. Treatment with AgOAc gave (S_p)‐Me₂‐CAP‐OAc which was applied to asymmetric transcyclopalladation (up to 78 % ee). The (R)‐N‐acetylphenylalanine mediated palladation methodology was applicable also to the corresponding N,N‐diethyl (82 % ee, 39 % yield) and pyrrolidinyl (>98 % ee, 43 % yield) cobalt sandwich complexes. A combination of 5 mol % of the latter [(S_p)‐Pyrr‐CAP‐Cl] and AgNO₃ (3.8 equiv) is a catalyst for the allylic imidate rearrangement of an (E)‐N‐aryltrifluoroacetimidate (up to 83 % ee), and this catalyst system is also applicable to the rearrangement of a range of (E)‐trichloroacetimidates (up to 99 % ee). This asymmetric efficiency combined with the simplicity of catalyst synthesis provides accessible solutions to the generation of non‐racemic allylic amine derivatives.