Thermal Intramolecular Diels-Alder Reaction of Furan (IMDAF)with N-bromofurfurylalkene; tert-butyl-5-bromo-7-methyl-10-oxa-3-aza-tricyclo[5.2.1.01,5]dec-8-eneSyntheticPage 235 (2005)
A contribution from the Demircan Group, Nigde
5-Methylfurfurylamine (Aldrich, distilled), 2,3-dibromipropene (Aldrich, distilled) ditertbutydicarboxylate (BOC)2O (Aldrich), n-BuLi(Aldrich).
Cycloaddition Reaction of N-(2-bromoally)-N-(tertbutoxycarbonyl)-5-methylfurfurylamine: The amines (5 mmol) was heated up to 110 oC in 10 mL of toluene for 4 days at which time the reaction mixture was cooled and concentrated. Purification by column chromatography afforded the cycloadducts, and in all cases, the polarity of the cycloadduct was greater that its precursor.
Synthsesis of IMDAF reaction's precursor was afforded, treatment of 2-methylfurfurylamine (2.3 mmol) with di-tert-butoxy dicarbonate (BOC)2O (0.55 g, 2.5 mmol) in DCM (10 mL) was added N,N-dimethylaminopyridine (30 mg, 0.25 mmol) at 0ºC. The reaction mixture was stirred for 2h at ambient temperature and then concentrated under reduced pressure. The residue was used for alkylation without further purification using n-BuLi and 2,3-dibromopropene in THF at -78oC.
tert-butyl-5-bromo-7-methyl-10-oxa-3-aza-tricyclo[5.2.1.01,5]dec-8-ene: As a white solids, 0.66 g (40 %) m.p.: 85-87oC. TLC, (Hexane: Diethylether; (5:1)) Rf: 0.22; IR(KBr)(cm-1: 2975(C-H), 1699(C=O), 1479. PNMR (CDCl3, 300MHz): 6.3(d, 1H, J 5.8 Hz), 6.2(d, 1H, J 5.8 Hz), 4.30(dd, 2H, J1 6.0 Hz, J2 12.5 Hz), 3.96(dd, 2H, J1 6.0 Hz, J2 12.0 Hz), 2.06(d, 1H, J 12.5 Hz), 1.70(d, 1H, J 12.5 Hz), 1.68(m, 1H), 1.5 (s, 3H), 1.45(s, 9H). 13CNMR (75.5 MHz): 154.5, 136.8, 135, 95.9, 79.8, 75.4, 64.4, 54.5, 51.9, 48.2, 28.7(3xC), 21.5. m/z (GC-MS): 331[M+(81Br), 8%], 329[M+(79Br), 8%], 274[M+(81Br)-(tBu-H), 18%], 272[M+(79Br)-(tBu-H), 18%], 230[M+(81Br)-(Boc), 44%], 228[M+(79Br)-(Boc), 44%], 57[tBu+, 100%]. EA (C14H20BrNO3): Requires: C 50.92 %, H, 6.10 %, N, 4.24 %, Found: C 51.22 %, H 5.86 %, N, 4.40 %.
A. Demircan and P. J. Parsons, Synlett, 1215 (1998); A. Demircan and P. J. Parsons, Heterocycl. Commun., 8, 531, (2002).
I. N. N. Namboothiri, M. Ganesh, S. M. Mobin, M. Cojocaru, J. Org. Chem., 70, 2235, (2005).P. G. Sammes and D. J. Weller, Synthesis, 1205 (1995)
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