The Journal of Organic Chemistry
Article
13C{1H} NMR (100 MHz, CDCl3) δ 162.0, 158.5, 135.4, 133.0,
120.7, 111.0, 108.5, 86.2, 84.1, 56.0 ppm.
121.1, 113.5, 113.2, 26.8 ppm. HRMS (ESI-TOF) m/z: C14H12N3O
[M + H]+ calcd for 238.0975, found 238.0979.
3-(2-Fluorophenyl)propiolic Acid (2s).18 Purification by flash
chromatography (EtOAc) gave a grey solid (128.0 mg, 78%). MP =
1-(2-(1H-Benzo[d]imidazol-1-yl)pyridin-3-yl)ethan-1-one (L4).
The ligand was synthesized following a previously reported method.19
Purification by flash chromatography (PE/EA, 2:1) gave a white solid
(290.1 mg, 24%). MP = 216.2−217.4 °C. 1H NMR (400 MHz,
CDCl3) δ 8.36−8.35 (m, 1H), 7.98 (d, J = 8.0 Hz, 1H), 7.92−7.90
(m, 1H), 7.66 (d, J = 8.0 Hz, 1H), 7.41−7.37 (m, 1H), 7.33−7.29 (m,
1H), 7.18−7.14 (m, 1H), 6.56 (s,1H), 1.98 (s, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 151.7, 148.7, 134.6, 132.6, 124.7, 123.9, 120.4,
120.1, 112.8, 71.8, 25.8 ppm. HRMS (ESI-TOF) m/z: C14H12N3O
[M + H]+ calcd for 238.0975, found 238.0978.
1-(3-(1H-Benzo[d]imidazol-1-yl)phenyl)ethan-1-one (L5). The
ligand was synthesized following a previously reported method.19
Purification by flash chromatography (PE/EA, 2:1) gave a white solid
(960.9 mg, 81%). MP = 78.4−79.5 °C. 1H NMR (400 MHz, CDCl3)
δ 8.14 (s, 1H), 8.10 (t, J = 1.6 Hz, 1H), 8.03−8.01 (m, 1H), 7.89−
7.87 (m, 1H), 7.74−7.66 (m, 2H), 7.53−7.51 (m, 1H), 7.36−7.32
(m, 2H), 2.66 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 196.8,
144.2, 142.1, 139.0, 137.0, 133.5, 130.6, 128.3, 127.9, 124.1, 123.5,
123.2, 120.9, 110.3, 26.8. HRMS (ESI-TOF) m/z: C15H13N2O [M +
H]+ calcd for 237.1022, found 237.1022.
1
115.7−116.2 °C. H NMR (600 MHz, DMSO-d6) δ 7.71 (t, J = 7.5
Hz, 1H), 7.63−7.59 (m, 1H), 7.40 (t, J = 9.0 Hz, 1H), 7.32 (t, J = 7.5
Hz, 1H). 13C{1H} NMR (150 MHz, DMSO-d6) δ 163.3 (d, C-F, 1JC‑F
= 251.0 Hz), 154.5, 135.0, 133.9 (d, C-F, 3JC‑F = 8.4 Hz), 125.6 (d, C-
F, 4JC‑F = 3.6 Hz), 116.5 (d, C-F, 2JC‑F = 20.0 Hz), 108.0 (d, C-F, 2JC‑F
= 15.0 Hz), 86.8, 76.1 19F NMR (376 MHz, DMSO-d6) δ −107.0
ppm.
3-(2-Chlorophenyl)propiolic Acid (2t).6a Purification by flash
chromatography (EtOAc) gave a white solid (139.0 mg, 77%). MP
1
= 136.4−136.8 °C. H NMR (400 MHz, CDCl3) δ 7.64 (d, J = 6.0
Hz, 1H), 7.47 (d, J = 6.4 Hz, 1H), 7.42 (t, J = 6.2 Hz, 1H), 7.31 (t, J =
6.0 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3) δ 158.1, 137.8,
135.1, 132.2, 129.8, 126.9, 119.6, 85.2, 84.3 ppm.
3-(Thiophen-2-yl)propiolic Acid (2u).18 Purification by flash
chromatography (EtOAc) gave a gray solid (126.3 mg, 83%). MP =
1
138.3−140.5 °C. H NMR (400 MHz, DMSO-d6) δ 7.89 (d, J = 5.2
Hz, 1H), 7.68 (d, J = 3.6 Hz, 1H), 7.21 (t, J = 4.4 Hz, 1H). 13C{1H}
NMR (100 MHz, DMSO-d6) δ 154.1, 137.0, 132.8, 128.3, 118.2,
85.8, 78.5 ppm.
1-(6-Acetylpyridin-2-yl)-3-methyl-1H-benzo[d]imidazol-3-ium
Iodide (C1). Organocatalyst C1 was synthesized following a
previously reported method.14a−c Purification by flash chromatog-
raphy (DCM/MeOH, 10:1) gave a white solid (276.8 mg, 73%). MP
= 238.1−238.4 °C. 1H NMR (400 MHz, DMSO-d6) δ 10.63 (s, 1H),
8.63−8.61 (m, 1H), 8.49 (t, J = 8.0 Hz, 1H), 8.29 (d, J = 8.0 Hz, 1H),
8.21−8.17 (m, 2H), 7.86−7.80 (m, 2H), 4.23 (s, 3H), 2.78 (s, 3H).
13C{1H} NMR (100 MHz, DMSO-d6) δ 197.8, 152.1, 146.7, 143.2,
3-(Thiophen-3-yl)propiolic Acid (2v).11a Purification by flash
chromatography (EtOAc) gave a white solid (109.5 mg, 72%). MP
1
= 155.2−156.9 °C. H NMR (600 MHz, DMSO-d6) δ 8.19 (dd, J =
1.2, 3.0 Hz, 1H), 7.70 (dd, J = 3.0, 4.8 Hz, 1H), 7.33 (dd, J = 1.2, 5.4
Hz, 1H). 13C{1H} NMR (150 MHz, DMSO-d6) δ 154.4, 134.9, 130.0,
127.8, 117.9, 81.6, 80.4 ppm.
3-Cyclopropylpropiolic Acid (2w).4d Purification by flash chroma-
tography (EtOAc) gave a white solid (80.3 mg, 73%). MP = 62.6−
142.1, 132.3, 129.3, 128.0, 127.3, 122.0, 120.6, 115.8, 114.1, 33.9, 26.2
ppm. HRMS (ESI-TOF) m/z: C15H14IN3O [M − I]+ calcd for
252.1131, found 252.1136.
1
63.9 °C. H NMR (400 MHz, DMSO-d6) δ 1.54−1.47 (m, 1H),
0.96−0.91 (m, 2H), 0.81−0.77 (m, 2H). 13C{1H} NMR (100 MHz,
DMSO-d6) δ 154.2, 92.1, 69.5, 8.9, 1.2 ppm.
1-(6-Acetylpyridin-2-yl)-3-ethyl-1H-benzo[d]imidazol-3-ium Io-
dide (C2). Organocatalyst C2 was synthesized following a previously
reported method.14a−c Purification by flash chromatography (DCM/
MeOH, 10:1) gave a white solid (314.6 mg, 80%). MP = 218.2−219.1
°C. 1H NMR (400 MHz, DMSO-d6) δ 10.59 (s, 1H), 8.65−8.62 (m,
1H), 8.49 (t, J = 8.0 Hz, 1H), 8.34 (d, J = 8.0 Hz, 1H), 8.26−8.19 (m,
2H), 7.85−7.79 (m, 2H), 4.66 (q, J = 14.8 Hz, 2H), 2.77 (s, 3H),
1.65 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz, DMSO-d6) δ
197.9, 152.0, 146.8, 142.5, 142.0, 131.4, 129.5, 128.0, 127.3, 121.9,
120.8, 116.1, 114.1, 42.9, 26.2, 14.0 ppm. HRMS (ESI-TOF) m/z:
C16H16IN3O [M − I]+ calcd for 266.1288, found 266.1282.
1-(6-Acetylpyridin-2-yl)-3-propyl-1H-benzo[d]imidazol-3-ium Io-
dide (C3). Organocatalyst C3 was synthesized following a previously
reported method.14a−c Purification by flash chromatography (DCM/
MeOH, 10:1) gave a white solid (309.5 mg, 76%). MP = 213.3−214.7
°C. 1H NMR (400 MHz, DMSO-d6) δ 10.66 (s, 1H), 8.65−8.63 (m,
1H), 8.49 (t, J = 8.0 Hz, 1H), 8.35 (d, J = 8.0 Hz, 1H), 8.29−8.27 (m,
1H), 8.20 (d, J = 7.6 Hz, 1H), 7.86−7.79 (m, 2 H), 4.61 (t, J = 8.0
Hz, 2H), 2.78 (s, 3H), 2.07 (q, J = 14.8 Hz, 2H), 1.03 (t, J = 7.6 Hz,
3H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 197.8, 152.0, 146.8,
142.7, 141.9, 131.7, 129.5, 128.0, 127.3, 121.9, 120.8, 116.0, 114.2,
48.8, 26.2, 22.0, 10.8 ppm. HRMS (ESI-TOF) m/z: C17H18IN3O
calcd for [M − I]+ 280.1444, found 280.1448.
1-(6-Acetylpyridin-2-yl)-3-propyl-1H-benzo[d]imidazol-3-ium
Bromide (C4). Organocatalyst C4 was synthesized following a
previously reported method.14a−c Purification by flash chromatog-
raphy (DCM/MeOH, 10:1) gave a white solid (259.2 mg, 72%). MP
= 238.5−238.7 °C. 1H NMR (400 MHz, DMSO-d6) δ 10.82 (s, 1H),
8.66−8.64 (m, 1H), 8.49 (t, J = 8.0 Hz, 1H), 8.40 (d, J = 8.0 Hz, 1H),
8.30−8.28 (m, 1H), 8.19 (d, J = 7.6 Hz, 1H), 7.85−7.78 (m, 2H),
4.63 (t, J = 7.2 Hz, 2H), 2.78 (s, 3H), 2.07 (q, J = 14.8 Hz, 2H), 1.02
(t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz, DMSO-d6) δ 235.5,
189.6, 184.5, 180.5, 179.6, 169.4, 167.1, 165.6, 164.9, 159.5, 158.5,
153.5 151.9, 86.4, 63.9, 59.7, 48.5 ppm. HRMS (ESI-TOF) m/z:
C17H18BrN3O [M-Br]+ calcd for 280.1444, found 280.1449.
4,4-Dimethyl-2-pentynoic Acid (2x).6a Purification by flash
chromatography (EtOAc) gave a dark green liquid (89.4 mg, 71%).
1H NMR (400 MHz, CDCl3) δ 1.22 (s, 9H). 13C{1H} NMR (100
MHz, CDCl3) δ 154.6, 94.9, 72.9, 29.8, 27.2 ppm.
Hept-6-en-2-ynoic Acid (2y).6a Purification by flash chromatog-
1
raphy (EtOAc) gave a dark green liquid (73.2 mg, 58%). H NMR
(400 MHz, CDCl3) δ 2.36 (t, J = 6.8 Hz, 2H), 1.50−1.43 (m, 2H),
1.40−1.31 (m, 2H), 0.88 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 192.0, 126.1, 111.9, 66.9, 59.1, 55.0, 51.0 ppm.
Propyl 3-Phenylpropiolate (4a). Purification by flash chromatog-
1
raphy (PE/EA, 10:1) gave a colorless liquid (114.2 mg, 60%). H
NMR (400 MHz, CDCl3) δ 7.60−7.58 (m, 2H), 7.47−7.43 (m, 1H),
7.39−7.35 (m, 2H), 4.20 (t, J = 6.8 Hz, 2H), 1.75 (q, J = 14.0 Hz,
2H), 0.99 (t, J = 7.6 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ
154.4, 133.1, 130.7, 128.7 119.8, 86.2, 80.8, 67.8, 22.0, 10.5 ppm.
HRMS (EI-TOF) calcd for C10H12O2 [M]+ 188.0837, found
188.0833.
1-(6-(1H-Benzo[d]imidazol-1-yl)pyridin-2-yl)ethan-1-one (L2).
The ligand was synthesized following a previously reported method.19
Purification by flash chromatography (PE/EA, 2:1) gave a white solid
(902.6 mg, 76%). MP = 119.4−120.6 °C. 1H NMR (400 MHz,
CDCl3) δ 8.61 (s, 1H), 8.14 (d, J = 7.2 Hz, 1H), 8.02−8.09 (m, 2H),
7.90 (d, J = 7.2 Hz, 1H), 7.78 (m, 1H), 7.45−7.37 (m, 2H), 2.80 (s,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ 198.9, 153.0, 149.3, 144.9,
141.2, 140.2, 132.1, 124.7, 123.8, 121.0, 119.5, 117.5, 112.8, 26.2
ppm. HRMS (ESI-TOF) m/z: C14H12N3O [M + H]+ calcd for
238.0975, found 238.0976.
1-(6-(1H-Benzo[d]imidazol-1-yl)pyridin-3-yl)ethan-1-one (L3).
The ligand was synthesized following a previously reported method.19
Purification by flash chromatography (PE/EA, 2:1) gave a white solid
(925.4 mg, 78%). MP = 175.3−176.7 °C. 1H NMR (400 MHz,
CDCl3) δ 9.15 (d, J = 1.6 Hz, 1H), 8.67 (s, 1 H), 8.45−8.43 (m, 1H),
8.19−8.17 (m, 1H), 7.89−7.86 (m, 1H), 7.68 (d, J = 8.0 Hz, 1H),
7.45−7.37 (m, 2H), 2.69 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3)
δ 195.3, 152.7, 150.4, 145.1, 141.3, 138.9, 132.0, 130.3, 124.9, 124.1,
1-(6-Acetylpyridin-2-yl)-3-propyl-1H-benzo[d]imidazol-3-ium
Chloride (C5). Organocatalyst C5 was synthesized following a
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J. Org. Chem. 2021, 86, 1850−1860