References and Notes
-
Reviews:
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1a
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Selected references:
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5a
Hormuth S.
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5b
Okala Amombo MG.
Hausherr A.
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5d
Flögel O.
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5e
Kaden S.
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5f
Helms M.
Schade W.
Pulz R.
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Fiera L.
Hlobilová I.
Zahn G.
Reissig H.-U.
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Mantione R.
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For selected recent syntheses of 2,5-disubstituted dihydropyrroles:
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7a
Jones AD.
Knight DW.
Redfern AL.
Gilmore J.
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7b
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Kagoshima A.
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7d
Hausherr A.
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7e
Ma S.
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7f
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Headley CE.
Cousins RPC.
Cowley A.
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999
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7g
Morita N.
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Zhu X.-F.
Henry CE.
Kwon O.
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Dieter RK.
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7j
Ohno H.
Kadoh Y.
Fujii N.
Tanaka T.
Org. Lett.
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For selected recent syntheses of 2,5-disubstituted dihydrofurans:
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8a
Hoffmann-Röder A.
Krause N.
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8b
Chen J.
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Franck B.
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9b
Boivin TLB.
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9d
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9e
Trost BM.
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9g
Basler B.
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Larock RC.
J. Org. Chem.
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12a
Olsson L.-I.
Claesson A.
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12b
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12c
Flögel O.
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Isolation and structural determination:
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13a
Matkhalikova SF.
Malikov VM.
Yunusov SY.
Khim. Prir. Soedin.
1969,
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13b
Matkhalikova SF.
Malikov VM.
Yunusov SY.
Khim. Prir. Soedin.
1969,
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Previous syntheses of this compound:
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13c
Iida H.
Yamazaki N.
Kibayashi C.
J. Org. Chem.
1987,
52:
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13d
Severino EA.
Correia CRD.
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13f
Toyao A.
Tamura O.
Takagi H.
Ishibashi H.
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13g
Haddad M.
Larchevêque M.
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13h
Chandrasekhar S.
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Prakash SJ.
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Heathcock CH.
Blumenkopf TA.
Smith KM.
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1989,
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11
Conversion of 9 into 13; Typical Procedure
To a solution of 1-methoxy-4-(3-methoxy-1-propynyl)ben-zene (9; 1.20 g, 6.82 mmol) in Et2O (15 mL) n-BuLi (2.5 M in hexane, 2.73 mL, 6.82 mmol) was added at -78 °C and stirred for 1 h. MeOH (276 µL, 6.82 mmol) was added slowly to the mixture and the resulting solution was warmed with stirring to r.t. (0.5 h). The mixture was cooled again to -78 °C and n-BuLi (2.73 mL, 6.82 mmol) was added slowly and the resulting solution was stirred for 0.5 h. Imine 11 (1.34 g, 6.82 mmol) dissolved in Et2O (15 mL) was slowly transferred to the reaction flask by syringe. After stirring for 1.5 h at -78 °C to -20 °C, the mixture was quenched with H2O and the aqueous phase was extracted with Et2O (3 × 25 mL). The combined organic phases were washed with brine (25 mL) and dried with MgSO4. Filtration and evaporation of solvents in vacuo at r.t. afforded allenyl amine 12 (3.17 g, dr ca. 50:50), which was used for the subsequent cyclization without purification. The crude product was dissolved in anhyd MeCN (45 mL); K2CO3 (2.35 g, 17.0 mmol) followed by AgNO3 (289 mg, 1.70 mmol) were added to the solution. The resulting mixture was stirred for 16 h in the dark under argon, then filtered through a pad of celite, washed with EtOAc, and the filtrate was concentrated in vacuo at r.t. The resulting product was purified by column chromatography on silica gel (hexane-EtOAc, 4:1) to give 13 (1.98 g, 78% from 9) as a mixture of diastereomers (trans/cis 45:55). Isomers (2,5-trans)-13 (650 mg, 25%) and (2,5-cis)-13 (1.12 g, 44%) were separated by fractional crystallization.
3-Methoxy-5-(4-methoxyphenyl)-2-methyl-1-tosyl-2,5-dihydro-1
H
-pyrrole (2,5-
trans
)-13. Colorless crystals; mp 138-140 °C. IR (KBr): 3100-3000 (=CH), 3000-2840 (CH), 1670 (C=C), 1610 (CN), 1340, 1160 (RSO2N) cm-1. 1H NMR (500 MHz, CDCl3): δ = 1.63 (d, J = 6.3 Hz, 3 H, Me), 2.31 (s, 3 H, Ts-Me), 3.62, 3.77 (2 s, 3 H each, OMe), 4.40-4.52 (m, 2 H, 2-H, 5-H), 5.50 (dd, J = 1.9, 4.7 Hz, 1 H, 4-H), 6.55-6.65, 6.90-7.00, 7.00-7.10 (3 m, 2 H, 4 H, 2 H, Ar). 13C NMR (126 MHz): δ = 20.9, 21.4 (2 q, Me), 55.4, 57.1 (2 q, OMe), 60.2 (d, C-2), 67.5 (d, C-5), 94.6 (d, C-4), 113.3, 126.7, 128.8, 129.9 (4 d, Ar), 132.1, 138.4, 141.9, 159.4 (4 s, Ar), 157.8 (s, C-3). MS (EI, 80 eV, 30 °C):
m/z (%) = 373 (30) [M]+, 358 (13) [M - CH3]+, 266 (26) [M - C7H7O]+, 218 (100) [M - C7H7SO2]+, 155 (40) [C7H7SO2]+. HRMS (EI, 80 eV, 30 °C): m/z calcd for C20H23NO4S: 373.13478; found: 373.13450. Anal. Calcd for C20H23NO4S (373.5): C, 64.32; H, 6.21; N, 3.75. Found: C, 64.29; H, 6.32; N, 3.69.
(2,5-
cis
)-13. Brownish liquid. IR (KBr): 3100-3000 (=CH), 3000-2840 (CH), 1665 (C=C), 1610 (CN), 1350, 1160 (RSO2N) cm-1. 1H NMR (500 MHz, CDCl3): δ = 1.50 (d, J = 6.3 Hz, 3 H, Me), 2.39 (s, 3 H, Ts-Me), 3.54, 3.78 (2 s, 3 H each, OMe), 4.30-4.42 (m, 2 H, 2-H, 5-H), 5.35 (m, 1 H, 4-H), 6.80-6.90, 7.20-7.35, 7.60-7.65 (3 m, 2 H, 4 H, 2 H, Ar). 13C NMR (126 MHz): δ = 21.6, 21.8 (2 q, Me), 55.4, 57.3 (2 q, OMe), 60.3 (d, C-2), 67.2 (d, C-5), 94.0 (d, C-4), 113.8, 127.7, 128.4, 129.6 (4 d, each, Ar), 134.9, 135.5, 143.4, 159.2 (4 s, Ar), 157.3 (s, C-3). MS (EI, 80 eV, 30 °C): m/z (%) = 373 (8) [M]+, 358 (2) [M - CH3]+, 266 (11) [M - C7H7O]+, 218 (48) [M - C7H7SO2]+, 217 (100), 155 (9) [C7H7SO2]+. HRMS (EI, 80 eV, 30 °C): m/z calcd for C20H23NO4S: 373.13478; found: 373.13432.