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  • 1
    Digitale Medien
    Digitale Medien
    Synthesis of donor-substituted 2-benzopyrans, isoquinolines, and cinnolines with acetal structure (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1303-1312 
    Details
    ISSN: 0947-3440
    Schlagwort(e): Central nervous system agents ; Bromine-lithium exchange ; 2-Benzopyrans ; Spiro[2-benzopyran-1,4′-piperidines] ; Isoquinolines ; Cinnolines ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: At -105°C the aryllithium intermediate 7, which was generated by treatment of the donor-substituted bromo acetal 6 with n-butyllithium, was trapped with aromatic and aliphatic aldehydes, with paraformaldehyde, with a ketone, an amide, an imine, and an azo compound to yield the hydroxy acetals 9a-c and 18, the homophthalaldehyde derivative 8, the amino acetal 24 and the hydrazino acetal 28. The acid-catalyzed ring closure of the hydroxy acetals 9a-c and 18, the amino acetal 24, and the hydrazino acetal 28 provided the 2-benzopyrans 10a-c, 19 and 20, the isoquinoline 26, and the cinnolines 29 and 30, respectively. Hydrogenolysis (H2, Pd/C) of the benzyl-protective group led to the phenols 15a-c, 21, 31, and 32. The spiropiperidines 21 and 22 showed a very low affinity for the phencyclidine binding site of the NMDA receptor. In mice weakly sedative effects were caused by application of 21 and 22.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1995199507173
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  • 2
    Digitale Medien
    Digitale Medien
    Diastereoselective Addition of Chiral (2-Lithiophenyl)acetaldehyde Acetals to Various Imines as Key Step in the Asymmetric Synthesis of 1-Aryltetrahydroisoquinolines, Part 4 (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 503-517 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Enantiomerically pure (2-bromophenyl)acetaldehyde acetals ; Halogen-metal exchange ; Diastereoselective addition to imines ; Asymmetric synthesis ; Tetrahydroisoquinolines ; NMDA antagonists ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: -A novel asymmetric synthesis of 1-aryl-1,2,3,4-tetrahydroisoquinolines has been developed. The key step in this synthesis is the diastereoselective addition of homochiral (2-lithiophenyl)acetaldehyde acetals to the sulfonylimine 25 and to the arylimines 28 and 31. The best diastereoselectivity is obtained by addition of the bis(2-methoxypropan-2-yl)-substituted 1,3-dioxolane 6e to benzylidene-p-anisidine (31) with an HPLC-determined diastereomeric ratio 32c/33c = 92.1:7.9. The N-tosyl and the N-(4-methoxyphenyl) groups of the addition products 26d, 27d, 32c, and 33c are cleaved with sodium in liquid ammonia and ammonium cerium(IV) nitrate, respectively, to yield the primary amines 35 and 36. The acid-catalysed cyclization of the sulfonamides 26d and 27d and the carbamates 37 and 38, prepared from 35 and 36, leads to the enantiomerically pure dihydroisoquinolines 40 and 41, respectively. During the cyclization of the sulfonamides 26d, 27d and the carbamates 37, 38 the chiral auxiliary - the diol 39 - is cleaved unchanged and can be recovered in good yields.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Preparation of Chiral 2-(2-Bromobenzyl)-1,3-dioxolanes and Their Addition to Acylimines (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 711-718 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Asymmetric synthesis ; (2-Bromophenyl)acetaldehyde acetals, enantiomerically pure ; Bromine-lithium exchange ; 1-Phenyl-1,2,3,4-tetrahydroisoquinoline ; NMDA antagonists ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of enantiomerically pure 2-(2-bromobenzyl)-1,3-dioxolanes 10 has been prepared by transacetalization of the dimethyl acetal 8 or the enol ether 7 with enantiomerically pure C2 symmetric 1,2-diols. We investigated the ability of the chiral 1,3-dioxolane moiety to control the diastereoselectivity during the addition of the aryllithium intermediates 18 to the acylimines 17. Those reactive aryllithium species were generated by bromine/lithium exchange at the bromo acetals 10. In this series the best diastereoselectivity was obtained by addition of the aryllithium intermediate 18b to the acylimine 17a to yield the diastereomeric addition products 19c/20c in a ratio of 72:28. After separation, the main diastereomer 19c was cyclized to afford the dihydroisoquinoline (R)-21, which was then hydrogenated to give the NMDA antagonistic 1-phenyl-1,2,3,4-tetrahydroisoquinoline (R)-2. The chiral auxiliary, the diol 9b, cleaved during the cylization of 19c, could be recovered in 89% yield.
    Materialart: Digitale Medien
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