Page 7 of 10
The Journal of Organic Chemistry
in DMSO following the above general procedure and purifi-
tert-Butyl (S)-2-(1-((diphenylmethylene)amino)but-3-en-1-yl)-
1
2
3
4
5
6
7
8
cation by flash chromatography (1% Et3N in 3% EtOAc/PE)
afforded homoallylic imine 2j (0.03 g, 0.11 mmol, 41%) as a
white solid: mp 109.9–120.0 °C; Rf = 0.5 (1% Et3N in 5%
1H-indole-1-carboxylate (2n). Ni-catalyzed DcA of imino ester
1n (0.07 g, 0.15 mmol) in DMSO following the above general
procedure and purification by flash chromatography (1%
Et3N in 3% EtOAc/PE) afforded homoallylic imine 2m (0.02
g, 0.05 mmol, 31%) as a colorless oil: Rf=0.69 (1% Et3N in 5%
EtOAc/PE); IR (NaCl film) 2982, 1735, 1456, 1375, 1334, 1161,
1117; [α]23.3D +9.58 (c 2.4 x 10-3 g/mL, CH2Cl2); 1H NMR (CDCl3,
400 MHz) 8.21 (d, J = 8.3 Hz, 1H), 7.76 – 7.71 (m, 2H), 7.47
(d, J = 7.1 Hz, 1H), 7.43 – 7.35 (m, 7H), 7.24 – 7.17 (m, 2H),
7.06 (dd, J = 6.6, 3.0 Hz, 2H), 6.80 (s, 1H), 5.78 (ddt, J = 17.0,
10.2, 7.1 Hz, 1H), 5.28 – 5.15 (m, 1H), 5.10 – 4.93 (m, 3H), 2.67
(t, J = 6.4 Hz, 2H), 1.39 (s, 9H).; 13C{1H} NMR (CDCl3, 101
MHz) 168.3, 143.7, 139.9, 137.4, 137.0, 135.5, 130.1, 129.4, 128.7,
128.4, 128.1, 127.7, 123.5, 122.7, 120.2, 116.8, 115.6, 107.9, 83.7,
76.7, 60.5, 42.7, 27.9; HRMS (ESI-TOF) m/z: [M + H]+ Calcd
EtOAc/hexane); IR (NaCl film) 3050, 3024, 2360, 1503, 1407,
1
1343, 1013; [α]23.2 +4.25 (c 4 x 10-3 g/mL, CH2Cl2); H NMR
D
(CDCl3, 400 MHz) 7.74 – 7.65 (m, 3H), 7.44 – 7.29 (m, 6H),
7.19 (t, J = 7.2 Hz, 1H), 7.09 (td, J = 7.4, 1.4 Hz, 1H), 7.06 – 6.95
(m, 3H), 5.69 (ddt, J = 17.2, 10.1, 7.1 Hz, 1H), 5.04 – 4.90 (m,
2H), 4.63 (dd, J = 8.2, 4.9 Hz, 1H), 2.68 (ddd, J = 15.3, 8.2, 7.3
Hz, 1H), 2.56 – 2.45 (m, 1H), 2.33 (s, 1H), 1.90 (s, 3H); 13C{1H}
NMR (CDCl3, 101 MHz) 166.8, 143.3, 140.0, 137.5, 136.0, 134.1,
129.9, 128.5, 128.2, 128.0, 127.6, 126.1, 116.5, 62.4, 43.5, 19.0;
HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C24H24N+ 326.1903;
Found 326.1877. HPLC conditions: Chiral Technologies Di-
acel OD-H chiral column, eluent: 1:1000 2-propanol/hexane,
flow rate: 1 mL/min, average (S)-2j retention time = 5.326
min, average (R)-2j retention time = 6.699 min. The yields
reported in Scheme 2 are an average of three runs, which
provided 2j in isolated yields of 29%, 35%, and 41%, respec-
tively.
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17
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19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
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52
53
54
55
56
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60
+
for C30H31N2O2 451.2380; Found 451.2343. HPLC conditions:
Chiral Technologies Diacel OD-H chiral column, eluent:
1:1000 2-propanol/hexane, flow rate: 1 mL/min, average (S)-
2n retention time = 7.546 min, average (R)-2n retention time
= 8.594 min.General Procedure for the Ni-Catalyzed
Asymmetric DcA of Allyl 2,2-Diarylglycinate Imines 4. A
flame-dried screw-cap conical vial was charged with imine 4
(0.25 mmol) and a magnetic stir bar. The vial was capped
with a rubber septum, the contents degassed with three con-
secutive vacuum/argon-fill cycles, and then transported into
an inert environment glove box. Inside the glove box,
Ni(cod)2 (2.5 mol %) and (S,S)-f-binaphane (2.5 mol %) were
added to the vial which was then recapped, brought out of
the glove box, and placed under an Ar atmosphere. DMSO
(0.1 mL) was then added to the mixture via syringe and the
resulting mixture was stirred 25 °C (65 °C for 4d, 45 °C for 4i)
for 24 h. The reaction mixture was directly purified by flash
chromatography on SiO2 eluting with 1% Et3N in either 20%
EtOAc/PE. For determination of the regioisomeric ratios, the
products 5 were dissolved in MeOH, the imine was reduced
with NaBH3CN over 6 d, and the resultant product mixture
was analyzed by 1H NMR spectroscopy, as reported previous-
ly.8b In all cases, only a single product resulting from reduc-
tion on imines 5 was observed. Unless otherwise specified,
each reaction was repeated 2–4 times and the resulting er
values were averaged for the value reported in the main text
(Scheme 2). Homoallylic imine (S)-5a is a new compound
and was fully characterized (see below). All other homoallylic
imines (S)-5 spectroscopically matched previous reports.8b
(S)-N-(1-(3,5-dimethoxyphenyl)but-3-en-1-yl)-1,1-dipheny-
lmethanimine (2k). Ni-catalyzed DcA of imino ester 1k (0.10
g, 0.25 mmol) in DMSO following the above general proce-
dure and purification by flash chromatography (1% Et3N in
5% EtOAc/PE) afforded homoallylic imine 2k (0.06 g, 0.19
1
mmol, 76%) as a colorless liquid whose H NMR spectra
(CDCl3, 400 MHz) matched literature reports.8a The yields
reported in Scheme 2 are an average of three runs, which
provided 2k in isolated yields of 22%, 49%, and 76%, respec-
tively.
(S)-1,1-Diphenyl-N-(1-(4-methoxyphenyl)but-3-en-1-yl)-
methanimine (2l). Ni-catalyzed DcA of imino ester 1l (0.06 g,
0.16 mmol) in DMSO following the above general procedure
and purification by flash chromatography (1% Et3N in 5%
EtOAc/PE) afforded homoallylic imine 2l (0.03 g, 0.08 mmol,
1
52%) as a colorless oil whose H NMR spectra (CDCl3, 400
MHz) matched literature reports.8b The yields reported in
Scheme 2 are an average of three runs, which provided 2l in
isolated yields of 50%, 52%, and 54%, respectively.
(S)-N-(1-(3,4-dimethoxyphenyl)but-3-en-1-yl)-1,1-diphenyl-
methanimine (2m). Ni-catalyzed DcA of imino ester 1m (0.21
g, 0.67 mmol) in DMSO following the above general proce-
dure and purification by flash chromatography (1% Et3N in
10% EtOAc/PE) afforded homoallylic imine 2m (0.08 g, 0.23
mmol, 45%) as a colorless oil: Rf=0.69 (1% Et3N in 20%
Methyl (S)-4-(1-((bis(2-methoxyphenyl)methylene)amino-
but-3-en-1-yl)benzoate (5a). Ni-catalyzed DcA of imino ester
4a (0.04 g, 0.09 mmol) in DMSO following the above general
procedure and purification by flash chromatography (1%
Et3N in 10% EtOAc/PE) afforded homoallylic imine 5a (0.03
g, 0.08 mmol, 86%) as a white solid: mp 129.6–130.1 °C;
Rf=0.46 (1% Et3N in 20% EtOAc/PE); IR (NaCl film) 2943,
EtOAc/hexane); IR (NaCl film) 2934, 2836, 1599, 1524, 1447,
1
1268, 1027; [α]23.2 –7.36 (c1.4 x 10-2 g/mL, CH2Cl2); H NMR
D
(CDCl3, 400 MHz) 7.69 – 7.62 (m, 2H), 7.46 – 7.40 (m, 3H),
7.38 – 7.28 (m, 4H), 7.07 (dd, J = 6.5, 2.9 Hz, 2H), 6.90 (s, 1H),
6.79 (d, J = 0.8 Hz, 2H), 5.65 (ddt, J = 17.2, 10.2, 7.1 Hz, 1H),
5.04 – 4.90 (m, 2H), 4.37 (dd, J = 7.8, 5.6 Hz, 1H), 3.87 (d, J =
5.0 Hz, 6H), 2.68 (dt, J = 15.0, 7.6 Hz, 1H), 2.57 (dt, J = 13.6, 6.2
Hz, 1H). 13C{1H} NMR (CDCl3, 101 MHz) 147.7, 137.1, 135.8,
130.1, 129.8, 128.5, 128.1, 126.6, 119.0, 116.6, 110.8, 110.3, 66.2,
55.8, 44.0; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for
2833, 1723, 1604, 1491, 1438, 1277,1241; [α]23.2 –99.31 (c 4.32 x
D
1
10-3 g/mL, CH2Cl2); poor peak resolution in H and 13C{1H}
NMR due to hindered rotation about the aryl–C(imine) bond;
1H NMR (CDCl3, 400 MHz) 8.02 – 7.86 (m, 2H), 7.54 (dd, J
= 7.6, 3.6 Hz, 1H), 7.45 – 7.36 (m, 1H), 7.33 – 7.27 (m, 2H),
7.09 (dd, J = 13.7, 5.9 Hz, 1H), 7.03 – 6.88 (m, 2H), 6.79 (t, J =
16.8 Hz, 2H), 5.67 (s, 1H), 4.99 (d, J = 20.6 Hz, 2H), 4.40 (s,
1H), 3.90 (s, 2H), 3.83 (s, 1H), 3.57 (d, J = 2.1 Hz, 2H), 3.29 (s,
1H), 2.66 (t, J = 42.4 Hz, 2H); 13C{1H} NMR (CDCl3, 101 MHz)
157.3, 135.6, 130.1, 130.0, 129.3, 129.0, 125.6, 120.6, 117.8, 111.9,
66.2, 55.6, 52.0, 30.3; HRMS (ESI-TOF) m/z: [M + H]+ Calcd
+
C25H26NO2 372.1958; Found 372.1944. HPLC conditions: Chi-
ral Technologies Diacel OD-H chiral column, eluent: 1:1000
2-propanol/hexane, flow rate: 1 mL/min, average (S)-2m re-
tention time = 43.412 min, average (R)-2m retention time =
47.680 min. The yields reported in Scheme 2 are an average
of three runs, which provided 2m in isolated yields of 40%,
45%, and 50%, respectively.
7
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