A. G. Coyne et al. / Tetrahedron: Asymmetry 18 (2007) 199–207
205
130.9, 131.2, 134.8, 143.3 ppm. IR (KBr) m = 1548, 1662,
3050 cmꢀ1; LRMS (ES+) calcd for C13H11NO 197.1;
found m/z = 198.1 [M+1]+.
4.3.4.
(3R,4S)-3-(3,5-Bis(trifluoromethyl)phenyl)-1,4-di-
phenylazetidin-2-one 30. White solid. Conversion 64%.
20
Ee 53%, ½aꢁD ¼ þ19:0 (c 0.1, CHCl3). Mp 152–154 ꢁC.
1H NMR (CDCl3, 600 MHz) d = 4.34 (d, J = 2.6 Hz,
1H), 4.92 (d, J = 2.6 Hz, 1H), 7.03 (t, J = 7.3 Hz, 1H),
7.21 (t, J = 7.6 Hz, 2H), 7.27 (d, J = 7.74 Hz, 2H), 7.32–
7.38 (m, 5H), 7.73 (s, 1H), 7.78 (s, 1H) ppm. 13C NMR
(CDCl3, 600 MHz) d = 63.1, 64.0, 117.3, 122.0, 122.0,
122.1, 122.2, 124.6, 127.5–127.7 (m), 129.2, 129.3, 129.6,
132.4 (q, J = 33.7 Hz), 136.5, 137.0, 137.1, 163.5 ppm,
19F NMR (CDCl3, 282 MHz) d = ꢀ63.6 ppm. IR (KBr)
m = 1741 cmꢀ1 (C@O). LRMS calcd for C23H15F6NO
435.1; found m/z = 434.1 [Mꢀ1]. Anal. Calcd for
C25H15F6NO: C, 63.45; H, 3.47; N, 3.22. Found: C,
63.75; H, 3.57; N, 3.24.
The C,N-diarylnitrones 32, 35, 38 and 41 were all synthes-
ised according to the above procedure.
4.3. Synthesis of b-lactams
4.3.1. (3R,4R)-1,3,4-Triphenyl-2-azetidinone 6. A mixture
of copper(I)chloride (2.68 mg, 0.025 mmol) and ligand 16
(12.4 mg, 0.03 mmol) in dry acetonitrile (4 mL) was stirred
under a nitrogen atmosphere at ambient temperature for
2 h. The solution was cooled to 0 ꢁC and N,N-dicyclo-
hexylmethylamine (0.053 mL, 0.25 mmol) was added.
After 10 min phenyl acetylene (0.041 mL, 0.375 mmol)
was added. The mixture now a yellow colour was stirred
for a further 10 min. C,N-Diphenylnitrone 4 (0.049 g,
0.25 mmol) was added. The reaction was stirred at an
ambient temperature under a nitrogen atmosphere for
144 h (5 days). The reaction was passed through a short sil-
ica column using dichloromethane as the solvent. The res-
idue was concentrated in vacuo and placed onto a flash
column of silica gel (230–400 mesh ASTM). The product
4.3.5. (3R,4R)-4-(4-Methoxyphenyl)-1,3-diphenylazetidin-2-
one 33. White solid. Conversion 85%. Ee 32%.
20
1
½aꢁD ¼ þ6:8 (c 0.2, CHCl3). H NMR (300 MHz, CDCl3)
d = 3.67 (s, 3H), 4.99 (d, J = 6.3 Hz, 1H), 5.44 (d,
J = 6.3 Hz, 1H), 6.65 (dd, J = 2.1, 6.6 Hz, 2H), 7.00 (dd,
J = 2.4, 6.9 Hz, 2H), 7.06–7.14 (m, 6H), 7.24–7.31 (m,
2H), 7.40–7.43 (m, 2H) ppm. IR (KBr) m = 1726 cmꢀ1
(C@O). LRMS (ES+) calcd for C21H17NO 299.2; found
m/z = 300.2 [M+1]+.
was eluted with dichloromethane to yield the title com-
20
pound. Conversion 73%. Ee 37%, ½aꢁD ¼ þ13:0 (c 0.1,
CHCl3). 1H NMR (600 MHz, CDCl3) d = 4.94 (d,
J = 6.2 Hz, 1H), 5.39 (d, J = 6.2 Hz, 1H), 6.97–7.04 (m,
10H), 7.21 (app. t, 4H), 7.34 (app. d, 2H) ppm. 13C
NMR (600 MHz, CDCl3) d = 60.3, 60.4, 117.2, 124.0,
127.1, 127.9, 128.1, 128.2, 128.9, 129.1, 132.1, 134.4,
137.7, 165.6 ppm. IR (KBr) m = 1735 cmꢀ1 (C@O), LRMS
(ES+) calcd for C21H17NO 299.2; found m/z = 300.2
[M+1]+.
4.3.6. (3R,4R)-1,3-Diphenyl-4-(4-(trifluoromethyl)phenyl)-
azetidin-2-one 36. White solid. Conversion 64%. Ee
20
48%, ½aꢁD ¼ þ2:8 (c 0.2, CHCl3). 1H NMR (CDCl3,
300 MHz) d = 5.03 (d, J = 6.0 Hz, 1H), 5.52 (d,
J = 6.0 Hz, 1H), 7.07–7.20 (m, 8H), 7.30–7.45 (m, 8H)
ppm. 13C NMR (75 MHz, CDCl3) d = 59.6, 60.1, 117.2,
123.8 (q, J = 256 Hz), 124.3, 125.0 (q, J = 3.5 Hz), 126.8,
128.3, 128.5, 129.2, 129.9 (q, J = 41 Hz), 133.8, 136.3,
137.4, 164.6 ppm. IR (KBr) m = 1755 cmꢀ1 (C@O). LRMS
calcd for C22H16NO 367.2; found m/z = 366.2 [Mꢀ1].
4.3.2. (3R,4R)-3-(4-Methoxyphenyl)-1,4-diphenylazetidin-2-
one 23. Off-white solid. Conversion 22%. Ee 10%.
20
1
½aꢁD ¼ þ6:1 (c 0.1, CHCl3). H NMR (300 MHz, CDCl3)
d = 3.60 (s, 3H), 4.88 (d, J = 5.9 Hz, 1H), 5.36 (d,
J = 5.9 Hz, 1H), 6.54 (d, J = 8.5 Hz, 2H), 6.88 (d,
J = 8.4 Hz, 2H), 7.00–7.06 (m, 2H), 7.19–7.45 (m, 8H)
ppm. 13C NMR (75 MHz, CDCl3) d = 55.3, 60.0, 60.7,
113.8, 117.5, 120.3, 124.2, 124.4, 124.8, 127.2 127.4,
128.0, 128.5, 129.0, 129.3, 129.4, 130.2, 132.0, 134.7,
137.9, 166.3 ppm (one C-13 shift missing due to overlap),
IR (KBr) m = 1729 cmꢀ1 (C@O). LRMS (ES+) calcd for
C22H19NO2 229.2; found m/z = 330.2 [M+1]. Anal. Calcd
for C22H19NO2: C, 80.22; H, 5.81; N, 4.25. Found: C,
80.02; H, 5.72; N, 4.46.
4.3.7. (3R,4R)-4-(Naphthalen-1-yl)-1,3-diphenylazetidin-2-
one 39. Off-white solid. Conversion 78%. Ee 26%,
20
½aꢁD ¼ þ4:2 (c 0.2, CHCl3). Mp 204–205 ꢁC. 1H NMR
(CDCl3, 300 MHz) d = 5.18 (d, J = 6.1 Hz, 1H), 6.20 (d,
J = 6.1 Hz, 1H), 6.83 (dd, J = 1.8, 2.1 Hz, 2H), 6.86–7.54
(m, 18H), 7.59 (d, J = 8.1 Hz, 1H), 7.71 (d, J = 8.1 Hz,
1H), 7.96 (d, J = 8.2 Hz, 1H) ppm. 13C NMR (CDCl3,
75 MHz) d = 58.0, 61.1, 117.6, 122.7, 124.3, 125.0, 125.1,
125.9, 126.2, 127.5, 127.7, 128.4, 129.1, 129.4, 129.6,
130.8, 131.7, 133.5, 138.0, 166.2 ppm. IR (KBr)
m = 1732 cmꢀ1 (C@O). LRMS calcd for C25H19NO 349.1;
found m/z = 350.1 [M+1]. Anal. Calcd for C25H19NO: C,
85.93; H, 5.48; N, 4.01. Found: C, 85.92; H, 5.67; N, 3.92.
4.3.3. (3R,4R)-1,4-Diphenyl-3-(4-(trifluoromethyl)phenyl)-
azetidin-2-one 26. White solid. Conversion 80%. Ee
4.3.8. (3R,4R)-4-(Naphthalen-2-yl)-1,3-diphenylazetidin-2-
one 42. Off-white solid. Conversion 58%. Ee 41%.
20
1
29%. ½aꢁD ¼ þ3:2 (c 0.20, CHCl3). H NMR (300 MHz,
CDCl3) d = 5.06 (d, J = 6.0 Hz, 1H), 5.52 (d, J = 6.0 Hz,
1H), 7.02–7.13 (m, 6H), 7.19 (d, J = 8.4 Hz, 2H), 7.26–
7.40 (m, 6H) ppm. 13C NMR (75 MHz, CDCl3) d = 59.7,
60.5, 117.2, 123.7 (q, J = 256 Hz), 124.4, 125.2 (q,
J = 3.8 Hz), 127.5, 127.6, 128.3, 128.7, 129.2, 130.2 (q,
J = 40 Hz), 131.4, 137.3, 138.7, 142.3, 165.2 ppm. IR
(KBr) m = 1736 cmꢀ1 (C@O). LRMS (ES+) calcd for
C22H16NOF3 367.2; found m/z = 368.2 [M+1]+, (ESꢀ)
found m/z 366.2 [Mꢀ1]+.
20
½aꢁD ¼ þ9:1 (c 0.2, CHCl3). Mp 135–137 ꢁC, 1H NMR
(CDCl3, 300 MHz) d = 5.01 (d, J = 6.1 Hz, 1H), 5.54 (d,
J = 6.1 Hz, 1H), 6.88–7.04 (m, 8H), 7.17–7.21 (m, 2H),
7.31–7.37 (m, 3H), 7.46 (d, J = 8.5 Hz, 1H), 7.57–7.63
(m, 3H) ppm. 13C NMR (CDCl3, 75 MHz) d = 60.6, 60.8,
117.4, 124.3, 124.6, 126.3, 126.4, 126.9, 127.4, 127.9,
128.0, 128.3, 128.4, 129.0, 129.3, 132.2, 132.4, 138.0,
165.9 ppm. IR (KBr) m = 1732 cmꢀ1 (C@O). LRMS calcd
for C25H19NO 349.1; found m/z = 350.1 [M+1]. Anal.