References
1a
Arai S.
Shioiri T.
Tetrahedron Lett.
1998,
39:
2145
1b
Arai S.
Shioiri T.
Tetrahedron
2002,
58:
1407 ; and references cited therein
2a
Li A.-H.
Dai L.-X.
Aggarwal VK.
Chem. Rev.
1997,
97:
2341
2b
Aggarwal VK.
Calamai S.
Ford JG.
J. Chem. Soc., Perkin Trans. 1
1997,
593
2c
Aggarwal VK.
Ford JG.
Fonquerna S.
Adams H.
Jones RVH.
Fieldhouse R.
J. Am. Chem. Soc.
1998,
120:
8328
2d
Julienne K.
Metzner P.
Henryon V.
J. Chem. Soc., Perkin Trans. 1
1999,
731
2e
Aggarwal VK.
Winn CL.
Acc. Chem. Res.
2004,
37:
611
3
Jonczyk A.
Konarska A.
Synlett
1999,
1085
4
Typical Procedure for the Preparation of
p
-Substituted Benzyltriethylammonium Chlorides(1d).
A mixture of 4-chloromethyl-N,N-diethylbenzamide (2.25 g, 10 mmol) and Et3N (5.5 mL, 40 mmol) in acetone (5 mL) was heated under reflux for 16 h. Acetone was removed in vacuo and EtOAc was added. The formed colorless solid was filtered off to afford 4-diethylcarbamyl-benzyltriethylammonium chloride (1d, 2.27 g, 6.95 mmol) in 70% yield as white solid; mp 125-127 °C. 1H NMR (400 MHz, CDCl3): δ = 1.11 (m, 3 H), 1.26 (m, 3 H), 1.48 (t, 9 H, J = 7.3 Hz), 3.44 (m, 2 H), 3.47 (q, 8 H, J = 7.3 Hz), 5.03 (s, 2 H), 7.45 (d, 2 H, J = 8.4 Hz), 7.7 (d, 2 H, J = 8.1 Hz). 13C NMR (126 MHz, CDCl3): δ = 8.5, 12.9, 14.3, 39.4, 43.4, 53.2, 61.1, 127.3, 128.4, 133.0, 139.6, 170.0. IR (CHCl3): νmax = 2900, 1615, 1565, 1510 cm-1. HRMS (FAB+): m/z calcd for [C18H31N2O]+: 291.2436; found: 291.2434. Anal. Calcd for C18H31N2OCl·H2O: C, 62.7; H, 9.65; N, 8.12. Found: C, 62.55; H, 9.99; N, 8.12.
5 Quaternary ammonium salts containing methyl groups are known to promote 2,3-Stevens-type rearrangement reaction under strong basic condition. See: Marko IE. In
Comprehensive Organic Synthesis
Vol. 3:
Trost B.
Pergamon Press;
Oxford England:
1991.
p.913
6
Typical Procedure.
To an ice cooled stirred solution of 4-diethylcarbamyl benzyltriethylammonium chloride (1d, 326.8 mg, 1 mmol) and benzaldehyde (0.1 mL, 1 mmol) in THF (4 mL) was slowly added t-BuOK (224.4 mg, 2 mmol). Yellow colored suspension was stirred for 1 h at r.t. The mixture was diluted with CHCl3 and sat. aq NH4Cl. The mixture was separated and the aqueous layer was washed with H2O, brine, and then dried over MgSO4. Removal of the solvent and purification by flash chromatography (hexane-EtOAc = 1:1) afforded N,N-diethyl-4-(3-phenyloxiranyl)benzamide (2d, 264 mg, 89%) as a colorless solid; mp 83-85 °C. 1H NMR (400 MHz, CDCl3): δ = 1.20 (m, 6 H), 3.30 (m, 2 H), 3.54 (m, 2 H), 3.86 (d, 1 H, J = 1.83 Hz), 3.88 (d, 1 H, J = 1.83 Hz), 7.32-7.41 (m, 9 H). 13C NMR (126 MHz, CDCl3): δ = 13.0, 14.2, 39.3, 43.3, 62.4, 62.9, 125.6, 126.7, 128.5, 128.6, 136.9, 137.4, 138.2, 170.9. IR (CHCl3): νmax = 3000, 1612, 1565, 1510 cm-1. HRMS (EI+): m/z calcd for C19H21NO2: 295.1572; found: 295.1572. Anal. Calcd for C19H21NO2: C, 77.25; H, 7.17; N, 4.74. Found: C, 77.13; H, 7.28; N, 4.71. DABCO dissolved in the aqueous layer as an ammonium ion was recovered when the aqueous layer was basified by KOH and extracted with CH2Cl2.
7 Quinuclidine (the second N of DABCO is replaced by CH) was also tried as an amine candidate. The ammonium salt was formed but it was too moisture sensitive to be isolated. When one-pot and successive preparation of trans-2,3-diaryl epoxide was carried out using quinuclidine, 2h was obtained in 89%. Thus, the role of the second N of DABCO is not clear to date.
8 When carbonyl compounds such as aliphatic aldehydes and ketones, other than aryl aldehydes were used under the reaction condition, no epoxides were formed and carbonyl compounds were recovered.
9 According to the literature method,10 we have tried the reaction using benzylic chloride [e.g. (p-chloromethyl)benzonitrile, p-nitrobenzyl chloride] and benzaldehyde in the presence of phase-transfer catalyst. Corresponding epoxides were obtained in 88% and 70%, respectively, as diastereomeric mixtures.
10a
Dilling WL.
Hickner RA.
Farber HA.
J. Org. Chem.
1967,
32:
3489
10b
Taranko LB.
Perry RH.
J. Org. Chem.
1969,
34:
226
