Abstract
An efficient BF3·Et2O mediated conversion of Diels-Alder adduct 1 of Danishefsky’s diene and methyl acrylate yielded cyclohexenones 2 and 3. Subsequent reductive amination with several amines using NaBH(OAc)3 in acetic acid medium gave 4-alkylaminocyclohex-1-enecarboxylate derivatives (4a-e) in a concise form.
Key words
aminations - Diels-Alder reactions - enones - reductions - Danishefsky’s diene
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1H NMR (CDCl3, 300 MHz): δ = 1.09-1.28 (m, 2 H, H-2ax, H-6ax), 1.46 (qd, 2 H, J = 13, 3.5 Hz, H-3ax, H-5ax), 2.02 (m, 4 H, H-3, H-5), 2.28 (tt, 1 H, J = 12, 3.5 Hz, H-1), 2.51 (tt, 1 H, J = 11, 3.5 Hz, H-4), 3.66 (s, 3 H, OCH3), 3.82 (s, 2 H, CH2Ar), 7.20-7.40 (m, 5 H, Ar-H); 13C NMR (CDCl3, 75 MHz): δ = 27.7 (C-6, C-2), 32.3 (C-5, C-3), 42.9 (C-1), 51.0 (CH2Ar), 51.6 (OCH3), 55.5 (C-4), 126.9, 128.1, 128.4, 140.2 (Ar), 176.2 (CO).
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