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  • 1
    Electronic Resource
    Electronic Resource
    Phase Dependence of Conformational Motions in Solids. The tert-Butyl Rotation in (1R*,2S*,5R*)-5-tert-Butyl-2-hydroxycyclopentanecarboxylic Acid (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 2327-2335 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00113a022
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  • 2
    Electronic Resource
    Electronic Resource
    A Correlation Analysis of C:N 13C Chemical Shifts. The Use of Substituted Benzaldehyde (2-Hydroxycyclohexyl)hydrazones as Probes (1994)
    s.l. : American Chemical Society
    The @journal of organic chemistry 59 (1994), S. 5895-5900 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00099a016
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  • 3
    Electronic Resource
    Electronic Resource
    Basic forms of supramolecular self-assembly organized by parallel and antiparallel hydrogen bonds in the racemic crystal structures of six disubstituted and trisubstituted cyclopentane derivatives (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 539-550 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A selection of stereoisomeric 2-hydroxy-1-cyclopentanecarboxamides, a 4-tert-butyl derivative and three tert-butyl derivatives of the respective carboxylic acid were subjected to X-ray crystallography. The optically active molecules (I)–(VI) form racemic crystals. Each racemic structure is basically determined by two intermolecular hydrogen bonds of O—H...O=C—XH and O=C—X—H...OH types (X = O, NH). The partially similar patterns of close packing observed reflect five basic forms of supramolecular self-assembly. In the racemic crystals of chiral molecules, there are homo- and heterochiral chains of molecules formed by the principal (O—H...O=C) hydrogen bonds. These chains assemble either in a parallel or antiparallel mode. The parallel homochiral chains (hop) observed in structure (II), (1R*,2R*)-2-hydroxy-1-cyclopentanecarboxamide, demand the polar space group Pca21, while the parallel heterochiral chains (hep) are organized in antiparallel layers with space group P21/n in structure (VI), (1R*,2S*,5R*-5-tert-butyl-2-hydroxy-1-cyclopentanecarboxylic acid). Heterochiral chains in an antiparallel array (hea) are found in (I), (1R*,2S*)-2-hydroxy-1-cyclopentanecarboxamide, and (V) [(1R*,2S*4S*)-4-tert-butyl-2-hydroxy-1-cyclopentanecarboxylic acid, space group P21/c]. Structures (IV), (1R*,2S*,4R*)-4-tert-butyl-2-hydroxy-1-cyclopentanecarboxylic acid, and (III), (1R*,2R*,4S*)-4-tert-butyl-2-hydroxy-1-cyclopentanecarboxamide, reveal that homochiral chains in an antiparallel array (hoa; cross-linked by heterochiral dimers held together by the second hydrogen bonds) can be formed by either translation (space group P\bar 1) or a screw axis (space group P21/c). These alternatives are denoted hoa1 and hoa2. Similarly, within each pattern (hea, hep and hop) two slightly different alternatives can be expected. The partial similarities in the identified five patterns of hydrogen bonding are described by graph-set notations. Structures (I), (IV) and (V) can be characterized by a common supramolecular synthon, while the highest degree of similarity is shown by the isostructurality of (I) and (V).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768101006723
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  • 4
    Electronic Resource
    Electronic Resource
    Stereochemical studies, 73. Saturated heterocycles, 60 (1985)
    Springer
    Monatshefte für Chemie 116 (1985), S. 857-868 
    Details
    ISSN: 1434-4475
    Keywords: 1,1′-Carbonyldiimidazole ; Substituted 1,3-oxazine-2,4-diones with condensed skeleton ; IR ; 1H-NMR ; 3C-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung cis- undtrans-N-Alkyl-,N-Aralkyl- undN-Aryl-2,4-dioxo-, tri- und tetramethylen-perhydro-1,3-oxazine wurden aus 2-Carboxamido-1-cycloalkanolen und 1,1′-Carbonyldiimidazol dargestellt. Mit Hilfe der IR,1H- und13C-NMR Spektroskopie wurden die Struktur, diecis- odertrans-Annellierung der Ringe und die bevorzugte Konformation der flexiblencis-Isomeren im Vergleich zumcis-trans Isomerenpaar nachgewiesen. Ähnlich zu den früher untersuchten 1,3-Oxazine-2- und -4-onen ist hier ebenfalls das „O-endo“ Konformere bevorzugt; in diesem ist der Sauerstoffaxial angeordnet, und zwar unabhängig von der Zahl der alicyklischen Ringatome und dem flexibleren Oxazindionring.
    Notes: Abstract N-Substituted-2-carboxamido-1-cycloalkanols were cyclized with 1,1′-carbonyldiimidazole to synthesizecis- andtrans-N-alkyl-,N-aralkyl- andN-aryl-2,4-dioxo tri- and tetramethyleneperhydro-1,3-oxazines. The structures of the compounds and theircis ortrans ring anellation were confirmed by IR,1H- and13C-NMR spectroscopy, and thecis andtrans pairs of isomers were compared to establish the predominant conformation of the flexiblecis isomers. It was found that—similarly to the 1,3-oxazin-2- and -4-ones studied earlier—the “O-endo” conformers are preferred, in which the 1-oxygen atom isaxial to the alicyclic ring; this is independent of the number of ring atoms in the alicycle, and of the presence of an oxazinedione ring, even though this is more flexible that the ring of oxazinones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809162
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  • 5
    Electronic Resource
    Electronic Resource
    Stereochemical studies 98. Saturated heterocycles 100. Synthesis of stereoisomeric 2-ethylimino-3,1-perhydrobenzoxazines and benzothiazines (1987)
    Springer
    Monatshefte für Chemie 118 (1987), S. 503-509 
    Details
    ISSN: 1434-4475
    Keywords: 3,1-Perhydrobenzoxazines ; 3,1-Perhydrobenzothiazines ; Conformational analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Aus den stereoisomerencis- undtrans-2-Hydroxymethyl-1-cyclohexylaminen und ihrenN-Methyl- undN-Benzylderivaten (4 a–c,5 a–c) wurden mit Ethylisothiocyanat die entsprechenden Thiocarbamate (6 a–c,7 a–c) erhalten. Behandlung der Verbindungen6 und7 mit Methyljodid und anschließend Alkali ergab die 3,1-Perhydrobenzoxazine8 a–c,9 a–c, während mit HCl die Cyclisierung zu den 3,1-Perhydrobenzothiazinen10 a–c,11 a–c eintrat. Es wurde festgestellt, daß die bevorzugte Konformation derN-unsubstituiertencis-Isomeren8 a und10 a die „N-innen“-Form ist, während die derN-substituierten Derivate8 b,c und10 b,c bevorzugt in der „N-außen“-Form vorliegen.
    Notes: Abstract With ethyl isothiocyanate, the stereoisomericcis- andtrans-2-hydroxymethyl-1-cyclohexylamines and theirN-methyl andN-benzyl derivatives (4 a–c,5 a–c) furnished the corresponding thiocarbamates (6 a–c,7 a–c). Treatment of compounds6 and7 with methyl iodide and subsequent alkali treatment afforded 3,1-perhydrobenzoxazines8 a–c,9 a–c, while cyclization of compounds6 and7 to the 3,1-perhydrobenzothiazines10 a–c,11 a–c was performed with HCl. It was found that the predominant conformation of theN-unsubstitutedcis isomers8 a and10 a is theN-inside form, while theN-substituted derivatives8 b,c and10 b,c have theN-outside preferred conformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809932
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  • 6
    Electronic Resource
    Electronic Resource
    Correlation analysis of the 13C chemical shifts of substituted benzaldehyde 2-aminobenzoylhydrazones. Study of the propagation of substituent effects along a heteroatomic chain (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 55-66 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 13C chemical shifts of eight series of para- or meta-substituted benzaldehyde 2-aminobenzoylhydrazones possessing both amide and imine functionalities were measured. The 13C chemical shifts were used to study the transmission of electronic substituent effects along the heteroaromatic side-chain of the substituted aromatic ring. In addition to the C=N bond, the benzoylhydrazones possess in their side-chain polarizable C=O and phenyl π-units. The benzylidenic ring-substituent chemical shifts were analysed by the dual substituent parameter approach to separate the inductive and resonance effects. The negative ρI and ρR values observed (i.e. reverse substituent effects) indicate a significant π-polarization of the C=N bond. The highly negative ρR values, especially those in the case of meta substitution, suggest a contribution from a marked secondary field-transmitted resonance effect. The results are compared with those obtained for other hydrazones or imines. Variation of the electron-withdrawing ability of the N2 substituent is seen to have a systematic effect on the ρI values. Reverse substituent effects are also observed at the C-1″ site of the 2-aminobenzoyl ring while C-4″ shifts show normal behaviour, consistent with the general concept of the π-polarization that each π-unit of the side-chain is polarized largely as a localized system. Accordingly, the π-polarization effect is seen efficiently to propagate also along a heteroaromatic chain. On the other hand, the C=O sites exhibit normal, although fairly slight, dependence on the benzylidenic substituent indicating an insignificant role of π-polarization at that site. The effects of the solvent, CDCl3 vs. DMSO-d6, on the ρI and ρR values are also considered. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Fragmentation and intramolecular cyclization in cyclopentane-4,5-fused 2-N-phenyliminoperhydro-1,3-oxazines and related thiazines under electron impact ionization (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 615-624 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The influence of cyclopentane fusion on the fragmentation behaviour of 1,3-oxazines and related thiazines was studied. The differences observed in the rearrangement reactions between the hydrogen atom at the ortho position of the aromatic ring and one of the hetero atoms in the cyclohexane ring were also investigated. These rearrangements occur if the cyclohexane ring contains an electrophilic atom and the carbon atom next to it is substituted by a benzyl or arylamino group. The compounds examined were cis and trans isomers of the title compounds substituted with methyl and benzyl (in the latter case only the cis isomers) on the ring nitrogen. All the compounds exhibited a large [M — H]+ ion peak which decreased with increasing size of the substituent. This indicates an intramolecular cyclization prior to further fragmentation of the molecule. Methyl substitution seems to change the character of this intramolecular cyclization. The main routes of fragmentation resemble those of the cyclohexane-fused analogues more than those of the corresponding 5,6-fused compounds. The stereoisomers fragment so similarly that they cannot be distinguished from each other, except in the case of methyl substituted oxazines.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090716
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  • 8
    Electronic Resource
    Electronic Resource
    Electron ionization mass spectra of some cyclohexane fused 2-N-phenyliminoperhydro-1,3-oxazines and related thiazines (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 279-282 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The 70 eV electron ionization mass spectra of six cyclohexane fused 2-N-phenyliminoperhydro-1,3-oxazines and six related thiazines were recorded and their fragmentation patterns were studied by metastable-ion analysis and exact mass measurement. All the compounds examined lost a hydrogen atom from their molecular ion in a process best described as intramolecular cyclization. The most typical fragmentations were the loss of various alkyl radicals from the M+· or [M—H]+ ions with the simultaneous migration of one or more hydrogen atoms from the carbocyclic part to the heterocyclic part of the molecule. N-Substitution clearly affected the type and extent of different reactions. In general, the fragmentation patterns of the thiazine derivatives were more complicated than those of the related oxazines. In all cases studied, the cis- and trans-fused isomers gave rise to so similar spectra that their adequate differentiation was not possible.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040804
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  • 9
    Electronic Resource
    Electronic Resource
    Electronic effects in the electron ionization fragmentations of 2-aryl substituted octahydro-1,3- and -3,1-benzoxazines (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 465-469 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The 70 eV electron ionization mass spectra of 27 2-aryl substituted octahydro-1,3- and -3,1-benzoxazines have been recorded in order to find out how the site and stereochemistry of the ring fusion and especially the nature of the substitutent X on the 2-phenyl group affect their fragmentation patterns. The structural isomers showed clearly different spectra; however, stereoisomeric differentiation was possible only with 1,3-derivatives. The fragment-ion peaks connected with the ionized ring and open chain forms of the compounds studied were clearly present in all the spectra. Analogously to the results obtained in solution, the electron-withdrawing ability of X increased the abundance of the fragments originating from the ring form. Also, the relative importance of different fragmentation channels varied according to the electron donating or withdrawing ability of the substituent X.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070613
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  • 10
    Electronic Resource
    Electronic Resource
    Electron ionization mass spectra of some substituted stereoisomeric 1,6,7,11b-tetrahydro-2h,4H[1,3]oxazino[4,3-a]-isoquinolines and 1,6,7,11b-tetrahydro-2H[1,3]oxazino [4,3-a]-isoquinolin-4-ones1 (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 998-1002 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mass spectra often substituted oxazino[4,3-a]isoquinolines, two isoquino[2,1-c][1,3]benzoxazines and seven substituted oxazino[4,3-a]isoquinolin-4-ones were recorded under electron impact ionization. Fragmentations were examined by metastable ion analysis, collision induced dissociation and exact mass measurement. The oxazinoisoquinolines and oxazinoisoquinolin-4-ones behaved similarly, although there were a few differences in the fragmentation and especially in the peak intensities. The most important fragmentation began with the opening of the oxazole ring. The substituents affected the fragmentation of the isomeric compounds, whereas the spectra of the stereoisomeric compounds were identical. The two isoquinobenzoxazines differed noticeably from the other compounds in their fragmentation behaviour; the additional phenyl ring prompted entirely new fragmentations unique to this structure.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091105
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