A new synthesis of 8-oxabicyclo[3.2.1]octan-2-one and its use for the preparation of cycloheptane annulated furans

Synlett

Volumn , Issue 20, 2009, Pages 3349-3351

  Hopf, Henning ^a   Abhilash, K G ^a  

^a TECHNICAL UNIVERSITY OF BRAUNSCHWEIG   (Germany)

Author keywords

Annulated furan derivatives; Bicyclic ketones; Furan synthesis; Hetero cycles; Wittig Horner reactions

Indexed keywords

8 OXABICYCLO[3.2.1]OCTAN 2 ONE; BICYCLO COMPOUND; BORON TRIFLUORIDE; BORON TRIFLUOROETHERATE; CYCLOHEPTANE DERIVATIVE; FURAN DERIVATIVE; FURANOCYCLOHEPTANOL DERIVATIVE; KETONE; OCTANE; UNCLASSIFIED DRUG;

ARTICLE; CYCLIZATION; HORNER REACTION; REACTION ANALYSIS; SYNTHESIS;

EID: 72149083302     PISSN: 09365214     EISSN: 14372096     Source Type: Journal    
DOI: 10.1055/s-0029-1218371     Document Type: Article

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10. Representative Procedure To a suspension of NaH (67 mg, 60% suspension in oil, 1.67 mmol, 1.05 equiv) in dry THF (10 mL), cooled to 0 C, was added a solution of diethyl (2-oxopropyl)phosphonate (339 mg, 1.75 mmol, 1.1 equiv) in dry THF (10 mL) dropwise under nitrogen. After complete addition the reaction mixture was allowed to stir for 1 h at r.t. To this solution the ketone 9 (200 mg, 1.59 mmol, 1 equiv) was added, and the mixture was allowed to stir for 24 h at r.t. The reaction was quenched by the addition of H2O (50 mL) and worked up with Et2O (4 50 mL). The combined extracts were dried over anhyd Na2SO4 and concentrated. The residue was purified by column chromatography (Et2Opentane, 1:1) to afford the HWE adduct 17a (242 mg, 92%). To the HWE adduct (100 mg, 0.6 mmol, 1 equiv) in dry CH2Cl2 (15 mL), was added BF3OEt2 (128 mg, 0.9 mmol, 1.5 equiv), and the solution was allowed to reflux for 6 h. The reaction was quenched by the addition of sat. NaHCO3 solution and worked up by CH2Cl2 extraction. The combined extracts were dried over anhyd Na2SO4, filtered, and concentrated. The residue was purified by column chromatography (Et2Opentane, 1:1) to afford the furan 18a (82 mg, 82%) as a white amorphous solid. Compound 18a: white amorphous solid; mp 5557 C. IR (diamond ATR): nmax = 3333, 2941, 2920, 2981, 2581, 1578, 1493, 1442, 1251, 1022, 957, 904, 802 cm1. 1H NMR (200 MHz, CDCl3): d = 1.531.76 (m, 2 H), 1.86 (br s, 1 H), 1.952.10 (m, 2 H), 2.19 (s, 3 H), 2.252.40 (m, 2 H), 2.47 2.65 (m, 2 H), 2.772.90 (m, 1 H), 3.87 (tt, 1 H, J1 = 2.8 Hz, J2 = 9.1 Hz), 5.73 (s, 1 H). 13C NMR (50 MHz, CDCl3): d = 13.2, 21.0, 23.1, 34.9, 37.0, 73.4, 108.7, 120.4, 147.9, 150.0. HRMS (EI): m/z calcd for C10H14O2: 166.09938; found: 166.09902.Table 1 Generality of the Reaction.