References and Notes
1a
Wipf P.
Chem. Rev.
1995,
95:
2115
1b
Janvier P.
Sun X.
Bienayme H.
Zhu J.
J. Am Chem. Soc.
2002,
124:
2560
1c
Ikemoto N.
Miller RA.
Fleitz FJ.
Liu J.
Petrillo DE.
Leone JF.
Laquidara J.
Marcune B.
Karady S.
Armstrong JD.
Volante RP.
Tetrahedron Lett.
2005,
46:
1867
2a
Turchi IJ.
Dewar MJS.
Chem. Rev.
1975,
75:
389
2b
Wasserman HH.
McCarthy KE.
Prowse KS.
Chem. Rev.
1986,
86:
845
2c
Yeh VSC.
Tetrahedron
2004,
60:
11995
2d
Martin R.
Cuenca A.
Buchwald
SL.
Org. Lett.
2007,
9:
5521
2e
Herrera A.
Martinez-Alvarez R.
Ramiro P.
Molero D.
Almy J.
J.
Org. Chem.
2006,
71:
3026
2f
Davies JR.
Kane PD.
Moody CJ.
Tetrahedron
2004,
60:
3967
3a
Brahma S.
Ray JK.
J.
Heterocycl. Chem.
2008,
45:
311
3b
Li B.
Buzon RA.
Zhang ZJ.
Org.
Process Res. Dev.
2007,
11:
951
3c
Baumann M.
Baxendale IR.
Ley SV.
Smith CD.
Tranmer GK.
Org. Lett.
2006,
8:
5231
3d
Miller RA.
Smith RM.
Marcune B.
J. Org. Chem.
2005,
70:
9074
3e
Davies JR.
Kane PD.
Moody CJ.
Tetrahedron
2004,
60:
3967
3f
Xia Q.
Ganem B.
Synthesis
2002,
1969
3g
Ohba M.
Kubo H.
Seto S.
Fujii T.
Ishibashi H.
Chem.
Pharm. Bull.
1998,
46:
860
3h
Matsumoto K.
Suzuki M.
Yoneda N.
Miyoshi M.
Synthesis
1976,
805
3i
Possel O.
Van Leusen A.
Heterocycles
1977,
7:
77
3j
van Leusen AM.
Hoogenboom BE.
Siderius H.
Tetrahedron Lett.
1972,
13:
2369
For reviews, see:
4a
Welton T.
Chem.
Rev.
1999,
99:
2071
4b
Wasserscheid P.
Keim W.
Angew. Chem. Int. Ed.
2000,
39:
3772
4c
Parvulescu VI.
Hardacre C.
Chem. Rev.
2007,
107:
2615
4d
van Rantwijk F.
Sheldon RA.
Chem. Rev.
2007,
107:
2757
4e
Martins MAP.
Frizzo CP.
Moreira DN.
Zanatta N.
Bonacorso HG.
Chem. Rev.
2008,
108:
2015
4f
de Maria PD.
Angew. Chem. Int. Ed.
2008,
47:
2
5 Wu B., Zhang J., Zheng Z.-G., Yang
M., Yu X.-Q.; Chin. J. Chem.; 2008, in press
6
van Leusen AM.
Boerma GJM.
Helmholdt RB.
Siderius H.
Strating J.
Tetrahedron Lett.
1972,
2367
7
Sisko J.
Mellinger M.
Sheldrake PW.
Baine NH.
Tetrahedron Lett.
1996,
37:
8113
8
van Leusen AM.
Bouma RJ.
Possel O.
Tetrahedron Lett.
1975,
3487
9
Representative
Preparation of Monosubstituted TosMIC: 1-Bromobutane (5a; 0.206 g, 1.5 mmol) was added to the
mixture of TosMIC (4; 0.195 g, 1 mmol), K2CO3 (0.414
g, 3 mmol) and [bmim]Br (2.5 mL). After vigorous
stirring for 12 h at r.t., the mixture was poured into H2O
(10 mL), and was extracted with Et2O (3 × 10
mL). The combined organics were washed with H2O and brine.
The organic phase was dried over Na2SO4, and
concentrated in vacuum. The crude product was purified by chromatography on
silica gel (PE-EtOAc, 4:1) to provide pure compound 2a (95%).
10
Representative
Preparation of 4,5-Disubstituted Oxazoles: 1-Bromobutane (5a; 0.206 g, 1.5 mmol) was added to the
mixture of TosMIC (4; 0.195 g, 1 mmol), K2CO3 (0.414
g, 3 mmol) and [bmim]Br (2.5 mL). After vigorous
stirring 12 h at r.t., 4 was consumed,
and benzaldehyde (6a; 0.127 g, 1.2 mmol)
was added. After about 10 h of stirring, the mixture was poured
into H2O (10 mL), and was extracted with Et2O
(3 × 10 mL). The combined organics were washed with H2O
and brine. The organic phase was dried over Na2SO4,
and concentrated in vacuum. The crude product was purified by chromatography on
silica gel (PE-EtOAc, 10:1) to provide pure compound 7a (85%).
11
Spectroscopic
Data for Products:
Compound 2a: ¹H
NMR (400 MHz, CDCl3): δ = 0.91-0.95 (t, J = 14.4 Hz, 3 H), 1.33-1.49
(m, 3 H), 1.56-1.65 (m, 1 H), 1.79-1.88 (m, 1
H), 2.15-2.21 (m, 1 H), 2.48 (s, 3 H), 4.43-4.46
(m, 1 H), 7.41-7.44 (d, J = 8.0
Hz, 2 H), 7.85-7.87 (d, J = 8.4
Hz, 2 H). ¹³C NMR (100 MHz, CDCl3): δ = 13.7, 21.8,
21.8, 27.4, 28.2, 73.0, 130.1, 130.2, 131.2, 146.6, 164.9.
Compound 2b: ¹H NMR (400 MHz,
CDCl3): δ = 1.74-1.75 (d, J = 6.8 Hz, 3 H), 2.50 (s, 3
H), 4.60-4.65 (m, 1 H), 7.44-7.46 (d, J = 8.0 Hz, 2 H), 7.87-7.89
(d, J = 8.0 Hz, 2 H). ¹³C NMR
(100 MHz, CDCl3): δ = 15.5, 21.8, 68.3,
130.2, 130.7, 146.7, 164.6.
Compound 2c: ¹H
NMR (400 MHz, CDCl3): δ = 1.16-1.19 (t, J = 15.2 Hz, 3 H), 1.84-1.92
(m, 1 H), 2.23-2.29 (m, 1 H), 2.49 (s, 3 H), 4.38-4.42
(m, 1 H), 7.42-7.44 (d, J = 8.0
Hz, 2 H), 7.86-7.88 (d, J = 8.4
Hz, 2 H). ¹³C NMR (100 MHz, CDCl3): δ = 9.9,
21.8, 22.5, 74.2, 130.0, 130.2, 131.3, 146.6, 164.9.
Compound 2d: ¹H NMR (400 MHz,
CDCl3): δ = 0.86-0.90 (t, J = 13.6 Hz, 3 H), 1.27-1.37
(m, 10 H), 1.40-1.48 (m,
1 H), 1.58-1.65
(m, 1 H), 1.78-1.88 (m, 1 H), 2.14-2.22 (m, 1
H), 2.49 (s, 3 H), 4.43-4.47 (m, 1 H), 7.42-7.44
(d, J = 8.0 Hz, 2 H), 7.86-7.88
(d, J = 8.4 Hz, 2 H). ¹³C
NMR (100 MHz, CDCl3): δ = 14.3, 22.0,
22.8, 25.6, 28.6, 28.8, 29.2, 29.3, 31.9, 73.2, 130.3, 130.3, 131.4,
146.7, 165.1.
Compound 2e: ¹H
NMR (400 MHz, CDCl3): δ = 2.49 (s,
3 H), 2.96-3.02 (m, 1 H), 3.58-3.62 (m, 1 H),
4.58-4.61 (m, 1 H), 7.26-7.27 (m, 2 H), 7.29-7.37
(m, 3 H), 7.43-7.45 (d,
J = 8.0
Hz, 2 H), 7.90-7.92 (d, J = 8.4
Hz, 2 H). ¹³C NMR (100 MHz, CDCl3): δ = 21.8,
34.8, 74.2, 128.1, 129.1, 129.3, 130.2, 130.2, 131.2, 133.3, 146.8,
166.0.
Compound 2f: ¹H
NMR (400 MHz, CDCl3): δ = 2.49 (s,
3
H), 2.53-2.61 (m, 1 H), 2.95 (s, 1 H), 4.47-4.51
(m, 1 H), 5.28-5.33 (m, 2 H), 5.73-5.83 (m, 1
H), 7.43-7.45 (d, J = 8.0 Hz,
2 H), 7.87-7.89 (d, J = 8.4
Hz, 2 H). ¹³C NMR (100 MHz, CDCl3): δ = 21.8,
21.8, 29.7, 33.1, 72.3, 121.3, 121.4, 129.3, 130.2, 131.1, 146.7,
165.5.
Compound 2g: ¹H
NMR (400 MHz, CDCl3): δ = 1.16-1.18 (d, J = 6.8 Hz, 3 H), 1.21-1.22
(d, J = 6.4 Hz, 3 H), 2.48 (s, 3
H), 2.70-2.77 (m, 1 H), 4.33-4.34 (d, J = 3.6 Hz, 1 H), 7.41-7.43
(d, J = 8.0 Hz, 2 H), 7.86-7.88
(d, J = 8.0 Hz, 2 H). ¹³C
NMR (100 MHz, CDCl3): δ = 16.9, 20.8,
27.9, 30.9, 78.0, 129.6, 130.2, 133.0, 146.4, 165.5.
Compound 7a: ¹H NMR (400 MHz,
CDCl3): δ = 0.93-0.97 (t, J = 14.8 Hz, 3 H), 1.38-1.48
(m, 2 H), 1.69-1.77 (m, 2 H), 2.75-2.79 (t, J = 15.6 Hz, 2 H), 7.31-7.35
(t, J = 14.8 Hz,
1
H), 7.42-7.46 (t, J = 15.2
Hz, 2 H), 7.59-7.61 (d, J = 8.8 Hz,
2 H), 7.83 (s, 1 H). ¹³C NMR (100 MHz,
CDCl3): δ = 13.9, 22.5, 26.7, 30.8,
125.6, 127.8, 128.7, 129.0, 135.8, 145.3, 149.1. GC-MS
(ES): m/z = 201 [M]+.
Compound 7b: ¹H NMR (400 MHz,
CDCl3): δ = 0.92-0.96 (m,
3 H), 1.37-1.46 (m, 2 H), 1.68-1.75 (m, 2 H),
2.71-2.75 (t, J = 15.2
Hz, 2 H), 3.84 (s, 3 H), 6.96-6.98 (m, 2 H), 7.51-7.53
(m, 2 H), 7.80 (s, 1 H). ¹³C NMR (100
MHz, CDCl3):
δ = 13.9, 22.5,
26.6, 30.9, 55.3, 114.3, 121.7, 130.1, 130.1, 134.4, 145.4, 148.7,
159.3. GC-MS (ES): m/z = 231 [M]+.
Compound 7c: ¹H NMR (400 MHz,
CDCl3): δ = 0.92-0.96 (t, J = 14.8 Hz, 3 H), 1.37-1.47
(m, 2 H), 1.68-1.76 (m, 2 H), 2.38 (s, 3 H), 2.73-2.77
(t, J = 15.2 Hz, 2 H), 7.23-7.25
(d, J = 8.0 Hz, 2 H), 7.48-7.50
(d, J = 8.0 Hz, 2 H), 7.81 (s,
1 H). ¹³C NMR (100 MHz, CDCl3): δ = 13.9,
21.2, 22.5, 26.7, 30.9, 125.7, 126.2, 129.5, 135.2, 137.8, 145.5,
148.9. GC-MS (ES): m/z = 215 [M]+.
Compound 7d: ¹H NMR (400 MHz,
CDCl3): δ = 0.92-0.96 (t, J = 14.8 Hz, 3 H), 1.36-1.46
(m, 2 H), 1.67-1.75 (m, 2 H), 2.71-2.74 (t, J = 15.2 Hz, 2 H), 7.10-7.16
(m, 2 H), 7.53-7.58 (m, 2 H), 7.81 (s, 1 H). ¹³C
NMR (100 MHz, CDCl3):
δ = 13.9,
22.5, 26.6, 30.8, 115.8, 116.0, 125.2, 125.2, 127.5, 135.5, 135.5,
144.6, 149.1, 161.0, 163.5. GC-MS (ES):
m/z = 219 [M]+.
Compound 7e: ¹H NMR (400 MHz,
CDCl3): δ = 0.93-0.96 (t, J = 14.8 Hz, 3 H), 1.39-1.44
(m, 2 H), 1.68-1.74 (m, 2 H), 2.72-2.76 (t, J = 5.6 Hz, 2 H), 7.45-7.47
(d, J = 8.8 Hz, 2 H), 7.56-7.58
(d, J = 8.4 Hz, 2 H), 7.84 (s,
1 H). ¹³C NMR (100 MHz, CDCl3): δ = 13.9,
22.5, 26.7, 30.7, 121.8, 127.1, 127.9, 128.1, 132.0, 136.4, 144.4,
149.3. GC-MS (ES):
m/z = 279 [M]+.
Compound 7f: ¹H NMR (400 MHz,
CDCl3): δ = 0.85-0.89 (t, J = 14.4 Hz, 3 H), 1.29-1.35
(m, 2 H), 1.61-1.67 (m, 2 H), 2.51-2.55 (t, J = 15.2 Hz, 2 H), 7.33-7.39
(m, 3 H), 7.49-7.51 (m, 1 H), 7.91 (s, 1 H). ¹³C
NMR (100 MHz, CDCl3):
δ = 13.8,
22.3, 25.7, 30.6, 126.7, 127.9, 130.2, 130.5, 131.8, 134.2, 137.9,
143.4, 150.2. GC-MS (ES): m/z = 235 [M]+.
Compound 7g: ¹H NMR (400 MHz,
CDCl3): δ = 0.94-0.97 (t, J = 14.8 Hz, 3 H), 1.38-1.47
(m, 2 H), 1.69-1.77 (m, 2 H), 2.75-2.78 (t, J = 15.2 Hz, 2 H), 7.29-7.31
(m, 1 H), 7.35-7.39 (t, J = 15.6
Hz, 1 H), 7.46-7.49 (m, 1 H), 7.59-7.60 (t, J = 3.6 Hz, 1 H), 7.84 (s, 1
H). ¹³C NMR (100 MHz, CDCl3): δ = 13.4,
22.5, 26.7, 30.7, 123.6, 125.6, 127.8, 130.0, 130.6, 134.8, 136.9,
144.1, 149.4. GC-MS (ES): m/z = 235 [M]+.
Compound 7h: ¹H NMR (400 MHz,
CDCl3): δ = 0.93-0.96 (t, J = 14.8 Hz, 3 H), 1.39-1.45
(m, 2 H), 1.68-1.76 (m, 2 H), 2.72-2.76 (t, J = 15.2 Hz, 2 H), 7.39-7.42
(m, 2 H), 7.51-7.53 (m, 2 H), 7.83 (s, 1 H). ¹³C
NMR (100 MHz, CDCl3):
δ = 13.9,
22.5, 26.7, 30.7, 126.8, 127.4, 129.0, 129.4, 129.4, 133.7, 136.3,
144.4, 149.2. GC-MS (ES): m/z = 235 [M]+.
Compound 7i: ¹H NMR (400 MHz,
CDCl3): δ = 0.95-0.99 (t, J = 14.8 Hz, 3 H), 1.42-1.48
(m, 2 H), 1.72-1.78 (m, 2 H), 2.82-2.86 (t, J = 15.6 Hz, 2 H), 7.77-7.79
(m, 2 H), 7.93 (s, 1 H), 8.30-8.32 (m, 2 H). ¹³C
NMR (100 MHz, CDCl3): δ = 13.9, 22.5,
27.1, 30.6, 124.3, 125.7, 128.1, 129.8, 134.9, 139.6, 143.5, 146.7,
150.3. GC-MS (ES): m/z = 246 [M]+.
Compound 7j: ¹H NMR (400 MHz,
CDCl3): δ = 0.82-0.86 (t, J = 14.8 Hz, 3 H), 1.26-1.35
(m, 2 H), 1.63-1.71 (m, 2 H), 2.55-2.59 (t, J = 15.6 Hz, 2 H), 7.50-7.56
(m, 4 H), 7.83-7.85 (m, 1 H), 7.89-7.95 (m, 2
H), 8.00 (s, 1 H). ¹³C NMR (100 MHz,
CDCl3): δ = 13.8, 22.4, 25.9, 31.0,
125.1, 125.5, 126.0, 126.3, 126.7, 128.4, 128.5, 129.8, 131.9, 133.8, 137.8,
145.2, 150.2. GC-MS (ES): m/z = 251 [M]+.
Compound 7k: ¹H NMR (400 MHz,
CDCl3): δ = 0.93-0.97 (t, J = 14.8 Hz, 3 H), 1.34-1.43
(m, 2 H), 1.63-1.71 (m, 2 H), 2.60-2.63 (t, J = 4.8 Hz, 2 H), 6.85-6.89
(d, J = 16.4 Hz,
1
H), 6.99-7.03 (d, J = 16.4
Hz, 1 H), 7.26-7.29 (t, J = 12.0 Hz,
1 H), 7.34-7.38 (t, J = 15.2
Hz, 2 H), 7.47-7.49 (d, J = 7.6
Hz, 2 H), 7.77 (s, 1 H). ¹³C NMR (100
MHz, CDCl3):
δ = 13.8, 13.9,
22.3, 31.0, 31.1, 112.5, 112.5, 126.4, 128.0, 128.0, 128.3, 128.4,
128.8, 128.8, 136.7, 136.7, 137.7, 145.1, 149.4, 149.4. GC-MS
(ES): m/z =
227 [M]+.
Compound 7l: ¹H NMR (400 MHz,
CDCl3): δ = 0.90-0.94 (t, J = 14.4 Hz, 3 H), 1.33-1.43
(m, 2 H), 1.64-1.71 (m, 2 H), 2.75-2.79 (t, J = 15.2 Hz, 2 H), 6.47-6.48
(m, 1 H), 6.54-6.54 (d, J = 3.2
Hz, 1 H), 7.47 (s, 1 H), 7.76 (s, 1 H). ¹³C NMR
(100 MHz, CDCl3): δ = 13.8, 22.3, 25.8,
30.8, 107.1, 111.3, 136.0, 138.6, 142.4, 149.0. GC-MS (ES): m/z = 191 [M]+.
Compound 7m: ¹H NMR (400 MHz,
CDCl3): δ = 0.87-0.93 (m,
9 H), 1.28-1.34 (m, 2 H), 1.53-1.59 (m, 2 H),
1.88-1.95 (m, 1 H), 2.37-2.43 (m, 4 H), 7.65 (s,
1 H). ¹³C NMR (100 MHz, CDCl3): δ = 13.9,
22.3, 22.4, 25.3, 28.1, 31.2, 33.5, 135.0, 146.5, 148.9. GC-MS
(ES): m/z = 181 [M]+.
Compound 7n: ¹H NMR (400 MHz,
CDCl3): δ = 0.89-0.92 (t, J = 14.4 Hz, 3 H), 1.26-1.35
(m, 6 H), 1.50-1.59 (m, 4 H), 1.70-1.83 (m, 4
H), 2.42-2.49 (m, 2 H), 2.60-2.66 (m, 1 H), 7.64
(s, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 13.9,
22.3, 25.3, 25.8, 26.3, 31.5, 31.7, 34.8, 132.7, 148.5, 151.1. GC-MS
(ES): m/z = 207 [M]+.
Compound 7o: ¹H NMR (400 MHz,
CDCl3): δ = 1.31-1.35 (t, J = 15.2 Hz, 3 H), 2.78-2.84
(m, 2 H), 7.32-7.35 (t, J = 14.8
Hz, 1 H), 7.41-7.46 (m, 2 H), 7.59-7.61 (d, J = 7.6 Hz, 2 H), 7.84 (s, 1
H). ¹³C NMR (100 MHz, CDCl3): δ = 13.1, 20.3,
125.7, 127.9, 128.8, 128.9, 136.9, 145.1, 149.2. GC-MS
(ES): m/z = 173 [M]+.
Compound 7p: ¹H NMR (400 MHz,
CDCl3): δ = 4.15 (s,
2 H),
7.19-7.28 (m, 4 H), 7.30-7.35 (m, 2 H), 7.40-7.43
(m, 2 H), 7.59-7.62 (m, 2 H), 7.87 (s, 1 H). ¹³C
NMR (100 MHz, CDCl3): δ = 32.9, 125.9,
126.5, 128.3, 125.5, 128.5, 128.6, 128.9, 133.9, 138.6, 146.6, 149.5.
GC-MS (ES): m/z = 235 [M]+.
Compound 7q: ¹H NMR (400 MHz,
CDCl3): δ = 0.89-0.92 (t, J = 14.8 Hz, 3 H), 1.58-1.67
(m, 2 H), 2.55-2.59 (t, J = 14.8
Hz, 2 H), 3.82 (s, 1 H), 7.11-7.22 (m, 4 H), 7.24-7.30 (m,
1 H), 7.70 (s, 2H). ¹³C NMR (100 MHz,
CDCl3): δ = 13.6, 21.6, 26.5, 32.1,
126.3, 128.5, 128.6, 133.2, 139.3, 148.0, 149.1. GC-MS
(ES): m/z = 235 [M]+.
Compound 7r: ¹H NMR (400 MHz,
CDCl3): δ = 3.53-3.54 (d, J = 6.0 Hz, 2 H), 5.12-5.14
(m, 1 H), 5.17 (s, 1 H), 6.00-6.10 (m, 1 H), 7.30-7.34
(t, J = 14.4 Hz, 1 H), 7.40-7.44
(t, J = 15.2 Hz, 2 H), 7.58-7.60
(d, J = 8.0 Hz, 2 H), 7.84 (s,
1
H). ¹³C NMR (100 MHz, CDCl3): δ = 31.4,
116.6, 125.8, 128.2, 128.6, 128.8, 133.1, 134.4, 146.2, 149.4. GC-MS (ES): m/z = 185 [M]+.
Compound 7s: ¹H NMR (400 MHz,
CDCl3): δ = 0.85-0.88 (t, J = 13.6 Hz, 3 H), 1.27 (s,
6 H), 1.55-1.60 (m, 2 H), 2.57-2.61 (t, J = 14.8 Hz, 2 H), 3.21-3.23
(d, J = 6.4 Hz, 2 H), 5.05-5.11
(m, 2 H), 5.87-5.96 (m, 1 H), 7.69 (s, 1 H). ¹³C NMR
(100 MHz, CDCl3): δ = 14.0, 22.5, 24.4,
28.1, 28.7, 30.2, 31.4, 116.0, 131.9, 135.2, 147.9, 148.9. GC-MS
(ES): m/z = 193 [M]+.
Compound 7t: ¹H NMR (400 MHz,
CDCl3): δ = 1.32-1.34 (t, J = 6.8 Hz, 6 H), 3.23-3.30
(m, 1 H), 7.32-7.36 (t, J = 15.2 Hz,
1 H), 7.43-7.46 (t, J = 15.2
Hz, 2 H), 7.57-7.60 (t, J = 8.4
Hz, 2 H) 7.84 (s, 1 H). ¹³C NMR (100
MHz, CDCl3): δ = 22.0, 25.7, 126.1,
128.0, 128.8, 129.0, 140.9, 144.2, 149.4. GC-MS (ES): m/z = 187 [M]+.
Compound 8a: ¹H NMR (400 MHz,
CDCl3): δ = 0.90-0.94 (t, J = 14.8 Hz, 6 H), 1.29-1.36
(m, 4 H), 1.38-1.46 (m, 2 H), 1.49-1.55 (m, 2
H), 1.88-2.05 (m, 4 H), 2.48 (s, 3 H), 7.40-7.42
(d, J = 8.0 Hz, 2 H), 7.85-7.87
(d, J = 8.4 Hz, 2 H).