МЕТОД ЭКСПЕРИМЕНТАЛЬНОГО ОПРЕДЕЛЕНИЯ МАГНИТНОГО МОМЕНТА НА ОСНОВЕ ПРОСТРАНСТВЕННОГО ГАРМОНИЧЕСКОГО АНАЛИЗА СИГНАТУР МАГНИТНОЙ ИНДУКЦИИ (original) (raw)
The reaction between allylmagnesium bromide and imines 5a-l leads to the corresponding 4-substituted 4-N-benzylaminobut-1-enes 6a-l, which were oxidized in a regioselective manner to the alkenylnitrones 7a-l. The intramolecular 1,3-dipolar cycloaddition of these nitrones gave 2-spiroannulated or 2-substituted 6-exo-phenyl-1-aza-7-oxabicyclo[2.2.1]heptanes 8a-j. Reductive cleavage of the N-O bond of the obtained bicycles afforded the diverse substituted 4-hydroxypiperidines 9a-h in good yields. This stereoselective approach allowed the preparation of all-cis-4hydroxy-6-phenyl-2-nonylpiperidine (9i), a close analogue of dendrobatid frog alkaloid 241D. A. Varlamov et al. PAPER Synthesis 2002, No. 6, 771-783 ISSN 0039-7881 © Thieme Stuttgart · New York 1.23 (d, J 3a,3b = 11.3) 1.82 (dd, J 3b,4 = 5.3) 4.89 (dt, J 4,5b = 2.6, J 4,5a = 2.6) c~2 .04 (m, J 5a,6a = 6.3) c C 6 D 6 -0.58 (d, J 3a,3b = 11.3 1.34 (ddd, J 3b,4 = 5.2, J 3b,5b = 2.4) 4.31 (t, J 4,3b = 5.2, J 4,5b = 5.2) 1.41 (dd, J 5a,5b = 11.3, J 5a,6a = 8.2) 8c CDCl 3 -1.36 (d, J 3a,3b = 11.3) 1.77 (dd, J 3b,4 = 5.2) 4.86 (dt, J 4,5b = 2.6) c~2 .03 (m, J 5a,6a = 6.3) c N O Ph R 2 R 1 1 2 3 4 5 6 α β β 8a-j PAPER A Stereoselective Route to All-cis-2,6-Disubstituted 4-Hydroxypiperidines 779 Synthesis 2002, No. 6, 771-783 ISSN 0039-7881 © Thieme Stuttgart · New York