Thermal Intramolecular Diels-Alder Reaction of Furan (IMDAF)with N-bromofurfurylalkene; tert-butyl-5-bromo-7-methyl-10-oxa-3-aza-tricyclo[5.2.1.0^1,5]dec-8-ene

Aydin Demircan (ademircan@nigde.edu.tr),
A contribution from the Demircan Group, Nigde

Chemicals Used
5-Methylfurfurylamine (Aldrich, distilled), 2,3-dibromipropene (Aldrich, distilled) ditertbutydicarboxylate (BOC)₂O (Aldrich), n-BuLi(Aldrich).

Procedure
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.

Author's Comments
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 -78^oC.

Data
tert-butyl-5-bromo-7-methyl-10-oxa-3-aza-tricyclo[5.2.1.0^1,5]dec-8-ene: As a white solids, 0.66 g (40 %) m.p.: 85-87^oC. 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 %.

Lead Reference
A. Demircan and P. J. Parsons, Synlett, 1215 (1998); A. Demircan and P. J. Parsons, Heterocycl. Commun., 8, 531, (2002).

Other References
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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