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  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Aminal-enamine Equilibrium in Cyclopropane-carbaminals.The following cyclopropane-carbaminals were synthesized: N,N′-(T-2,t-3-dimethyl-r-1-cyclopropyl)methylene-dipyrrolidin (15), the corresponding (c-2, c-3)-isomer 16, N,N′-(cyclopropyl)methylene-dipyrrolidin (17) and N,N′-(c-2, t-3-diphenyl-r-1-cyclopropyl)methylene-dipyrrolidin (18). Their constitutions and configurations were derived from the method of synthesis and from 1H-NMR.-spectra. The c-c-r-1-dimethyl-aminal 16 rearranged at room temperature to its t-t-r-1-dimethyl-isomer 15. This demonstrates the existance of an aminal-enamine equilibrium for cyclopropane-carbaminals although cyclopropane-carbenamines have not been isolated as yet. The kinetic data found for the rearrangement of 16 to 15 are compatible with two mechanisms: In the first one, the protonated aminal 21 decomposes into the iminium-ion 22, which, in turn, yields the enamine 19. In the second one, 21 is converted to 19 in a single step. The formation of cyclopropyl-pyrrolidino-acetonitrile (26) and dipyrrolidino-ethylene-1,1-dicarbonitrile (27) from the reaction of the aminal 17 with tetracyanoethylene may also be explained with an aminal-enamine equilibrium. - This equilibrium lies strongly on the side of the aminal. Investigations of the aminal-enamine ratio of several cycloalkanecarbaminals, namely of the 3-ring derivative 17, the 4-ring derivative 35 and the bicyclic 5-ring derivative 38, show that ring strain is a determining factor for the equilibrium bias. This strain may also explain that the aminomethanol 41 was isolable.Some of the aminals were synthesized from previously unknown aldehydes. t-2, t-3-dimethyl-r-1-cyclopropane-carbaldehyde (11) and its (c-2, c-3)-isomer 12 were obtained by stereoselective ring-contraction of the 2-chloro-cyclobutanols 46 and 48/49, respectively. The configurations of the aldehydes 11 and 12, of the starting cyclobutanones 44 and 45 and of the cyclobutanol 46 were established by 1H-NMR. measurements. From the steric course of the ring contraction it can be concluded that it is the fastest rearrangement of 2-halo-cyclobutanols with base, when the conformation having an equatorial halogen atom is not obstructed. c-2, t-3-diphenyl-r-1-cyclopropane-carbaldehyde (14) and 3-phenyl-1-cyclobutane-car-baldehyde (34) were synthesized by reduction of the corresponding ester 50 and acid 52, respectively, followed by Sarett-oxidation.
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative Aryl-Aryl-Coupling of 6,6′,7,7′-Tetramethoxy-1,1′,2,2′,3,3′,4,4′-octahydro-1,1′-biisoquinoline DerivativesWe describe the synthesis of 2 by intramolecular oxidative coupling of 1, 1′-biisoquinoline derivatives 1 (Scheme 1). This heterocyclic system can be considered as a union of two apomorphine molecules and may thus exhibit dopaminergic activity. - The readily available tetrahydrobiisoquinoline 6 was methylated to 11 (Scheme 4) and reduced (with NaBH3CN) to rac-7 and (catalytically) to meso-7 (Scheme 3). Reduction of 11 with NaBH4 and of the biurethane rac-9 with LiAlH4/AlCl3 afforded meso- and rac-10, respectively (Scheme 4). Demethylation of 6, meso-10, meso- and rac-7 led to 12, meso-14, meso- and rac-13, respectively (Scheme 5). The latter two phenols were converted with chloroformic ester to the hexaethoxycarbonyl derivatives meso- and rac-15 and subsequently saponified to the biurethanes meso- and rac-16, respectively (Scheme 5). - In order to assure proximity of the two aromatic rings, the ethano-bridged derivatives meso- and rac-18 were prepared by condensing meso- and rac-7 with oxalic ester and reducing the oxalyl derivatives meso- and rac-17 with LiAlH4/AlCl3, respectively (Scheme 6). The 1H-NMR, spectra at different temperatures showed that rac-18 populated two conformers but rac-17 only one, all with C2-symmetry, and that meso-17 as well as meso-18 populated two enantiomeric conformers with C1-symmetry. Whereas both oxalyl derivatives 17 were fairly rigid due to the two amide groupings, the ethano derivatives 18 exhibited coalescence temperatures of -20 and 30°. - The intramolecular coupling of the two aromatic rings was successful under ‘non-phenolic oxidative’ conditions with the tetramethoxy derivatives 7, 10 and 18, the rac-isomers leading to the desired dibenzophenanthrolines, the meso-isomers, however, mostly to dienones (Scheme 9): With VOF3 and FSO3H in CF3COOH/CH2Cl2 rac-7 was converted to rac-19, rac-18 to rac-21 and rac-10 to a mixture of rac-20 and the dienone 23b of the morphinane type. Under the same conditions meso-10 was transformed to the dienone 23a of the morphinane type, whereas meso-18 yielded the dienone 24 of the neospirine type, both in lower yields. The analysis of the spectral data of the six coupling products offers evidence for their structures. With the demethylation of rac-20 and rac-21 to rac-25 and rac-26, respectively, the synthetic goal of the work was reached, but only in the rac-series (Scheme 10). - In the course of this work two cleavages of octahydro-1,1′-biisoquinolines at the C(1), C(1′)-bond were observed: (1) The biurethanes 9 and 16 in both the meso- and rac-series reacted with oxygen in CF3COOH solution to give the 3,4-dihydroisoquinolinium salts 27 and 28; the latter was deprotonated to the quinomethide 30 (Scheme 11). (2) Under the Clarke-Eschweiler reductive-methylation conditions meso- and rac-7 were cleaved to the tetrahydroisoquinoline derivative 32.
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sechs Vinylketene (9a-9f), wovon fünf Chlor-vinylketene (9a-e) (s. Schema 2), in situ durch 1,4-Eliminierung von HCI aus den entsprechenden α, β-ungesättigten Säurechloriden hergestellt, wurden mit Cyclopentadien (2) bzw. 6,6-Dimethylfulven (3) umgesetzt. Durch [2 + 2]-Cycloaddition entstanden fünf 7-vinylsubstituierte Bicyclo[3.2.0]-2-hepten-6-one (10/11) bzw. drei 4-Isopropylidenbicyclo [3.2.0]-2-hepten-6-one (12/13), wobei das Stereoisomerenverhältnis 10:11 bzw. 12:13 von der Grösse der Ketensubstituenten beeinflusst wurde. Die Vinylketen-Cycloaddukte 10/11 und 12/13 enthalten ein Cope-System, das entweder in einer syn-(10 und 12) oder in einer anti-Konfiguration (11 und 13) vorliegt. Beim Erwärmen auf 140-190° ergaben 10/11 bzw, 12/13 durch Cope-Umlagerung die entsprechend substituierten Bicyclo[4.2.1]-3,7-nonadien-2-one (14) bzw. 9-Isopropylidenbicyclo[4.2.1]-3,7-nonadien-2-one (15). Mittels der beschriebenen Reaktionen werden die Ringsysteme von 14 und 15 in einer zweistufigen Synthese leicht zugänglich.
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conversion of Bicyclo [3.2.0]hept-2-en-6-one into Cyclopentadienylacetic Acid DerivativesThe reaction of a mixture of 4exo-bromobicyclo [3.2.0]hept-2-en-6-one (2) and -7-one (3) with O- or N-nucleophiles yielded cyclopentadien-5′-yl-acetates 4a-f or-acetamides 4g-h. Due to their rapid isomerization, the products 4 were not isolated, but some of them were demonstrated spectroscopically or captured in situ with maleimide as 10′-substituted norbornene derivatives 7. The formation of 4 from 2/3 involves a fragmentation of the bond between the carbonyl and the bridge-head C-atom, induced by the attacking nucleophile and the leaving Br-ion and aided by the relief of the four-membered ring strain. Some of the isomerization products of 4, i.e. the cyclopentadiene-1′-yl- and 2′-yl-acetyl derivatives were captured with maleimide as the 1′- and 8′-substituted norbornene-derivatives 8 and 9. Two C-nucleophiles did not induce the fragmentation: sodium acetylacetonate substituted the Br-atom and sodium (diethoxyphosphoryl)ethoxycarbonylmethide condensed with the carbonyl group of 2/3, yielding 11/12 and 13/14, respectively.
    Additional Material: 1 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 66 (1983), S. 2330-2341 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selected [2+2]-cycloadditions of three alkylvinylketenes 2 to one mono- and seven dialkyl-olefins 3 yielded eleven 2-alkyl-2-vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl-elimination from α,β-unsaturated acid chlorides 1; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]-cycloadditions were fully regio- and stereoselective with respect to the olefin 3, but less so with respect to the ketene 2, so that - where possible - two stereoisomers of 4 resulted, namely A and B, whose configurations were determined from their 1H-NMR, spectra, mechanistic considerations and, in one case, 4f, by chemical correlation with a previously known cycloadduct 8.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1379-1385 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A meta-Xylylene by Bamford-Stevens Reaction of a Fulvene-Ketene-AdductHeating the sodium salt 8 of the tosylhydrazone 4 of 4-isopropyliden-7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one (3; obtained by the addition of dimethylketene to 6,6-dimethylfulvene (1)), in diglyme at 130° led to the cotamethyl-[2.2]metacyclophane 10 (17%). The latter probably was formed by dimerization of the non-Kékulé molecule m-xylylene 14, which, in turn, could have arisen via the homofulvene 13 from the carbene 12. A second product in the thermolysis of 8 was the tricycle 9 (9 %), as a result of an intramolecular insertion of the carbene C-atom in 12 into a methyl C,H-bond. Further products were the azines 11a, 11b (50%), of the type known as byproducts in Bamford-Stevens reactions. Heating dry 8 afforded 9 (9%) and the two benzene derivatives 15 (9%) and 16 (3%). The tosylhydrazone 4 could be recovered by reaction of 11a, 11b with p-toluenesulfonohydrazide.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1828-1834 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Some 8-Substituted 2-Methyl-1,2,3,4-tetrahydroisoquinolinesA general route to 8-substituted tetrahydroisoquinolines is exemplified by the preparation of the 2-methyl-1,2,3,4-tetrahydroisoquinolin-8-ol (11), the -8-carbaldehyde oxime (12) and the -8-carbonitrile (13). It involves the conversion of isoquinoline (1) by partially modified Steps 1, 2, 3, and 5 (see the Scheme) into the 5-bromo-8-nitro derivative 5, reduction of the latter to the 8-amino derivative 8 and replacement of the NH2-group with an appropriate substituent by a Sandmeyer-like reaction. The selective reductions of the N-containing ring in 6 (Steps 5, 6, and 8) and of the NO2-group in 5 (Steps 4 and 7) were also studied.
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Course of the Intramolecular Diels-Alder-Reaction of Cyclopentadienes with Olefinic SubstituentsThe 1:3 mixture of 4-bromobicyclo [3.2.0]hept-2-en-6-one and -7-one (1/2), available by N-bromosuccinimide bromination of bicyclo [3.2.0]hept-2-en-6-one, reacted rapidly with the organo-magnesium and -zinc reagents 3, 10a, 10b and 10d by cyclobutanone ring opening and bromide ion expulsion to give the 5-substituted cyclopentadienes 5, 12a, 12b/12c, and 12d as non-isolated intermediates. Further transformation occured in situ either by a direct intramolecular Diels-Alder reaction (path a) or by a [1,5]-H-migration prior to the intramolecular Diels-Alder reaction (path b). The intermediate 5 followed only path a to give the bridged norbornene derivative 7, the intermediates 12a, 12b and 12c followed only path b to give the annellated norbornene derivatives 15a, 15b and 15c, respectively, and the intermediate 12d followed both paths to give the bridged 14d and the annellated norbornene derivative 15d (in the ration of about 1.4:1). These observations are discussed in terms of the relative velocities of [1,5]-H-migrations and intramolecular Diels-Alder reactions. The major conclusions are: (1) bridged norbornene derivatives with a six-membered ring C (such as 14d) can be prepared by an intramolecular Diels-Alder reaction from 5-alkenyl-cyclopentadienes 12, as long as the dienophilic double bond is activated by an appropriate substituent (as in 12d); (2) such 5-alkenyl-cyclopentadienes 12 are available from the reaction of the bromo-bicyclo-heptenones 1/2 with suitable C-nucleophiles 10.
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  • 9
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2]-cycloaddition of dichloroketene (prepared in situ from CCl3COCl and Zn(Cu)) with three alkynes 1a-c to form 2,3-dimethyl-(2a), 2,3-diethyl-(2b) and 3-butyl-4,4-dichlorocyclobut-2-enone (2c) proceeds rapidly in the absence of POCl3. The primary products 2a-c rearrange in situ to the 2,4-dichlorocyclobut-2-enones 3a-c under the influence of ZnCL2 produced during the reaction. ZnCl2 converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl-atoms of both 2a, b and 3a, band of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a-c. Without pyridine, this reduction gives ca. 1:1 mixtures of the double-bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD3COOD in the presence of pyridine. D-Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7, but rather a cyclobutenolate of type 8. The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1302-1306 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 6-step synthesis of (±)-grandisol (1) is presented, which involves dichloroketene addition to 3-methyl-3-butenyl acetate (4), reductive dechlorination of the adduct 6 to the ketone 7 and saponification to 8, aldolization of 7 or 8 with acetone and cyclization to the bicyclic ketone 9, Wolff-kishner, reduction to 14, and finally ring opening to 1. Since 9 is a known intermediate of the synthesis of (±)-lineatin (2), the latter can now be obtained in 6 steps.
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