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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of 5,5,10,10-tetramethyl-1-oxacyclotridecane-6,7,8,9-tetrone - on the mechanism of the Rubottom reactionDedicated to Professor Hans-Dieter Scharf on the occasion of his 65th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1655-1661 
    Details
    ISSN: 0947-3440
    Keywords: Cyclic vicinal tetraketones ; Rubottom reaction ; Medium-sized rings ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 5,5,10,10-tetramethyl-1-oxacyclotridecan-6,7,8,9-tetrone (12) was achieved via a multistep procedure involving an oxidation known as the Rubottom reaction. The key intermediates were the dialdehyde (25), the diacid (33), the cyclic diketone (39) and the bis(silyl enol ether) (42). The oxidation of 42 with mCPBA yielded two diastereomers, the syn and anti bis(α-hydroxy ketones) (44, 45) the ratio of which depends strongly on the solvent used. This result combined with the isolation of the diepoxide (43) gives an insight into the stereochemistry of the Rubottom reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199509230
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and Structures of Cyclotetradeca-4,11-diynone, Cyclotetradeca-4,11-diyne-1,8-dione, Their Exomethylene Derivatives, and 1,8-Dioxacyclotetradeca-4,11-diyneDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1545-1550 
    Details
    ISSN: 0947-3440
    Keywords: Medium-sized rings ; Alkynes ; Conformation analysis ; Ketones ; Cyclizations ; Ether ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following 14-membered ring diynes have been synthesized: cyclotetradeca-4,11-diynone (4), cyclotetradeca-4,11-diyne-1,8-dione (6), the corresponding exomethylene derivatives 5 and 7, as well as 1,8-dioxacyclotetradeca-4,11-diyne (8). The synthesis of the diketal of 4 was achieved by the reaction of the ethylene ketal of 1,5-dibromopentan-3-one (9) with the dilithium salt of 1,8-nonadiyne. Similarly, the diketal of 6 was prepared from the dilithium salt of the ethylene ketal of 1,8-nonadiyn-5-one 11 with 9. The unprotected ketones 4 and 6 were obtained by treating the ketals 10 and 14, respectively, with HCl. The ketones 4 and 6 were transformed to the exomethylene derivatives by a Wittig reaction. The reaction of the dilithium salt of 5-oxanona-1,8-diyne (16a) with 1,5-dibromo-3-oxapentane (15) yielded 8. X-ray investigations of single crystals of 6 and 8 revealed chair conformations with a zig-zag arrangement, employing two anti orientations of the two chains between the triple bonds. A zig-zag arrangement of the chain containing the carbonyl group was also found in 4. In 3b and 7 Ci symmetry was found, with only one anti conformation in each chain. Molecule 6 crystallizes with C2h symmetry and 8 with a center of symmetry.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970734
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular Structures of Cyclotetradeca-1,3,8,10-tetrayne and Cyclohexadeca-1,3,9,11-tetrayne (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2841-2843 
    Details
    ISSN: 1434-193X
    Keywords: Medium-sized rings ; Alkynes ; Structure elucidation ; X-ray diffraction ; Cyclic compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclotetradeca-1,3,8,10-tetrayne (3) and cyclohexadeca-1,3,9,11-tetrayne (4) have been prepared according to Sondheimer et al. The X-ray crystal structures of 3 and 4 reveal them to be in the chair conformation (3) and the twisted chair-chair-conformation (4). The tetrayne units in both molecules deviate considerably from linearity, giving rise to transannular distances of the terminal sp centers of 3.098(2) Å (3) and 4.147(2), 4.196(2) Å (4), and 3.390(2) Å (3) and 4.251(2), 4.252(2) Å (4) for the central sp atoms, respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation of 1-Azacyclododeca-3,8-diynes and 1,6-Diazacyclododeca-3,8-diynes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2113-2118 
    Details
    ISSN: 0947-3440
    Keywords: Medium-sized rings ; Cyclizations ; Alkynes ; Heterocycles ; Multicomponent reactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of N,N′-dialkyl- and N,N′-diaryl-1,6-diazacyclodeca-3,8-diynes was achieved by reaction of alkyl- or arylamines with 1,4-dihalobut-2-yne under dilution conditions in yields of 5-15%. The compounds synthesized by this procedure were the N,N′-dimethyl (2b), N,N′-diethyl (2c), N,N′-diisopropyl (2d), N,N′-di-tert-butyl (2e), N,N′-dicyclohexyl (2f), N,N′-diphenyl (2g), and N,N′-di-p-tolyl (2h) derivatives. The parent compound 2a was obtained in ca. 40% yield by heating 2d with α-chloroethylchloroformate (20). Using 1,9-dibromonona-2,7-diyne (10) and methylamine or isopropylamine, respectively, the corresponding N-alkyl-1-azacyclodeca-3,8-diynes 4b and 4d were synthesized under dilution conditions. By heating 4d with 20 we obtained 1-azacyclodeca-3,8-diyne (4a). As side products of the cyclization reactions the trimers 18 and tetramers 12 and 19 were isolated and characterized. N-methyl-1-azacycloundeca-3,9-diyne (14b) was prepared by reaction of 1,10-dibromodeca-3,8-diyne (13) with methylamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971013
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