The Journal of Organic Chemistry
Article
3033, 2982, 2934, 1743, 1454, 1371, 1242, 1065, 1029 cm−1. HRMS
(EI) m/z: [M]+ calcd for C10H12O2 164.0837; found 164.0841.
Cyclohexyl 2-Methylpropionate (4h).34 Purified by silica gel
column chromatography (eluent: n-pentane/Et2O = 20:1−2:1). 313.6
52.7, 33.9, 18.9 (2C), −0.2 (3C). IR (neat) 2971, 2187, 1743, 1471,
1387, 1339, 1252, 1187, 1148, 1052 cm−1. HRMS (DART+) m/z: [M
+ H]+ calcd for C10H19O2Si 199.1154; found 199.1159.
2-(2-Ethoxyethoxy)ethyl Pivalate (4o). Purified by silica gel
column chromatography (eluent: n-pentane/Et2O = 20:1−2:1).
1
mg, 92% yield [3 mol % 1aa, 4 h]. Yellow oil. H NMR (400 MHz,
1
CDCl3) δ 4.75 (m, J = 3.7 Hz, 1H), 2.51 (septet, J = 6.9 Hz, 1H),
1.88−1.66 (m, 4H), 1.48−1.22 (m, 6H), 1.16 (d, J = 6.9 Hz, 6H).
13C{1H} NMR (100 MHz, CDCl3) δ 176.8, 72.1, 34.3, 31.6 (2C),
25.5, 23.7 (2C), 19.1 (2C). IR (neat) 2937, 2860, 1732, 1454, 1386,
1342, 1260, 1195, 1162, 1072 cm−1. HRMS (DART+) m/z: [M +
H]+ calcd for C10H19O2 171.1385; found 171.1386.
385.5 mg, 88% yield [3 mol % 1aa, reflux, 24 h]. Yellow oil. H
NMR (400 MHz, CDCl3) δ 4.24−4.20 (m, 2H), 3.73−3.69 (m, 2H),
3.68−3.63 (m, 2H), 3.61−3.57 (m, 2H), 3.53 (q, J = 6.9 Hz, 2H),
1.25−1.19 (m, 12H). 13C{1H} NMR (100 MHz, CDCl3) δ 178.5,
70.7, 69.9, 69.2, 66.7, 63.6, 38.8, 27.2 (3C), 15.2. IR (neat) 2975,
2871, 1731, 1481, 1285, 1164, 1119 cm−1. HRMS (DART+) m/z: [M
+ H]+ calcd for C11H23O4 219.1596; found 219.1604.
Cyclododecyl Acetate (4i).35 Purified by silica gel column
chromatography (eluent: n-pentane/Et2O = 20:1−2:1). 449.3 mg,
99% yield [3 mol % 1aa, 2 h]; 453.9 mg, >99% yield [1 mol % 1aa, 7
h]. Yellow oil. 1H NMR (400 MHz, CDCl3) δ 5.00 (m, 1H), 2.03 (s,
3H), 1.78−1.62 (m, 2H), 1.58−1.30 (m, 20H). 13C{1H} NMR (100
MHz, CDCl3) δ 170.8, 72.2, 29.0 (2C), 24.0 (2C), 23.8, 23.3 (2C),
23.1 (2C), 21.3, 20.8 (2C). IR (neat) 2936, 2863, 1737, 1470, 1367,
1246, 1019 cm−1. HRMS (fast atom bombardment (FAB)+) m/z: [M
+ Na]+ calcd for C14H26NaO2 249.1830; found 249.1825.
(Tetrahydrofuran-2-yl)methyl Acetate (4p).39 Purified by silica gel
column chromatography (eluent: n-pentane/Et2O = 20:1−2:1). 286.7
1
mg, 99% yield [3 mol % 1aa, 3 h]. Yellow oil. H NMR (400 MHz,
CDCl3) δ 4.19−4.09 (m, 2H), 3.98 (dd, J = 11.0, 6.9 Hz, 1H), 3.90
(dt, J = 8.2, 6.9 Hz, 1H), 3.81 (dt, J = 8.7, 6.9 Hz, 1H), 2.10 (s, 3H),
2.06−1.85 (m, 3H), 1.60 (m, 1H). 13C{1H} NMR (100 MHz,
CDCl3) δ 171.1, 76.5, 68.5, 66.6, 28.0, 25.7, 21.0. IR (neat) 2975,
2874, 1742, 1449, 1370, 1239, 1085, 1041 cm−1. HRMS (DART+)
m/z: [M + H]+ calcd for C7H13O3 145.0865; found 145.0861.
Tropine Isobutyrate (4q).40 The reaction mixture was concen-
trated without extraction, and the residue was directly purified by
silica gel column chromatography (eluent: CHCl3/MeOH = 40:1).
346.7 mg, 82% yield [5 mol % 1aa, reflux, 24 h]. Yellow oil. 1H NMR
(400 MHz, CDCl3) δ 4.98 (t, J = 5.5 Hz, 1H), 3.10 (m, 2H), 2.52
(septet, J = 6.9 Hz, 1H), 2.28 (s, 3H), 2.12 (dt, J = 15.1, 4.6 Hz, 2H),
2.07−1.90 (m, 4H), 1.67 (d, J = 13.8 Hz, 2H), 1.18 (d, J = 6.9 Hz,
6H). 13C{1H} NMR (100 MHz, CDCl3) δ 176.2, 67.1, 59.9 (2C),
40.5, 36.7, 34.5 (2C), 25.7 (2C), 18.9 (2C). IR (neat) 2970, 2937,
1730, 1471, 1196, 1154, 1064, 1036 cm−1. HRMS (DART+) m/z: [M
+ H]+ calcd for C12H22NO2 212.1651; found 212.1653.
L-Menthyl Acetate (4j).36 Purified by silica gel column chromatog-
raphy (eluent: n-pentane/Et2O = 20:1−2:1). 383.8 mg, 97% yield [3
mol % 1aa, 2 h]; 397.6 mg, >99% yield [1 mol % 1aa, 7 h]. Yellow oil.
1H NMR (400 MHz, CDCl3) δ 4.67 (td, J = 10.6, 4.1 Hz, 1H), 2.04
(s, 3H), 1.99 (m, 1H), 1.86 (m, 1H), 1.72−1.63 (m, 2H), 1.48 (m,
1H), 1.36 (m, 1H), 1.13−0.82 (m, 3H), 0.90 (d, J = 6.4 Hz, 3H), 0.89
(d, J = 6.4 Hz, 3H), 0.76 (d, J = 6.9 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ 170.8, 74.2, 47.0, 41.0, 34.3, 31.4, 26.4, 23.5, 22.1,
21.4, 20.8, 16.4. IR (neat) 2955, 2871, 1736, 1456, 1370, 1245, 1025
cm−1. HRMS (ESI+) m/z: [M + H]+ calcd for C12H23O2 199.1698;
found 199.1701.
Isobornyl 2-Methylpropionate (4k).37 Purified by silica gel column
chromatography (eluent: n-pentane/Et2O = 20:1−2:1). 444.4 mg,
99% yield [3 mol % 1aa, 4 h]; 392.9 mg, 88% yield [1 mol % 1aa, 24
6-O-Acetyl-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose
(4r).41 Purified by silica gel column chromatography (eluent: n-
pentane/Et2O = 20:1−2:1). 587.8 mg, 97% yield [3 mol %, 2 M, 21
1
h]. Yellow oil. H NMR (400 MHz, CDCl3) δ 4.65 (dd, J = 7.8, 2.8
1
h]. White solid. m.p. 109−110 °C. H NMR (400 MHz, CDCl3) δ
Hz, 1H), 2.51 (septet, J = 6.9 Hz, 1H), 1.85−1.65 (m, 4H), 1.54 (m,
1H), 1.15 (d, J = 6.9 Hz, 3H), 1.21−1.01 (m, 2H), 1.14 (d, J = 6.9
Hz, 3H), 0.99 (s, 3H), 0.84 (s, 6H). 13C{1H} NMR (100 MHz,
CDCl3) δ 176.6, 80.6, 48.8, 47.0, 45.1, 38.9, 34.4, 33.8, 27.1, 20.2,
20.0, 19.1, 19.0, 11.5. IR (neat) 2955, 2877, 1733, 1456, 1389, 1344,
1260, 1199, 1157, 1071 cm−1. HRMS (EI) m/z: [M]+ calcd for
C14H24O2 224.1776; found 224.1770.
5.55 (d, J = 4.6 Hz, 1H), 4.62 (dd, J = 8.2, 2.8 Hz, 1H), 4.33 (dd, J =
5.0, 2.8 Hz, 1H), 4.29 (dd, J = 11.9, 4.6 Hz, 1H), 4.24 (dd, J = 8.2, 1.8
Hz, 1H), 4.19 (dd, J = 11.9, 7.8 Hz, 1H), 4.03 (ddd, J = 7.8, 5.0, 1.8
Hz, 1H), 2.09 (s, 3H), 1.52 (s, 3H), 1.45 (s, 3H), 1.34 (s, 3H), 1.33
(s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ 171.0, 110.0, 108.8,
96.3, 71.1, 70.7, 70.4, 65.9, 63.5, 26.0, 25.9, 25.0, 24.5, 20.9. IR (KBr)
3468, 1762, 1458, 1211 cm−1. HRMS (FAB+) m/z: [M + Na]+ calcd
for C14H22NaO7 325.1258; found 325.1275.
Bornyl Acetate (4l).38 Purified by silica gel column chromatog-
raphy (eluent: n-pentane/Et2O = 20:1−2:1). 384.4 mg, 98% yield [3
mol % 1aa, 2 h]; 393.6 mg, >99% yield [1 mol % 1aa, 5 h]. Yellow oil.
1H NMR (400 MHz, CDCl3) δ 4.88 (ddd, J = 10.1, 3.6, 2.3 Hz, 1H),
2.35 (m, 1H), 2.06 (s, 3H), 1.93 (m, 1H), 1.74 (m, 1H), 1.67 (t, J =
4.1 Hz, 1H), 1.33−1.20 (m, 2H), 0.97 (dd, J = 13.7, 3.6 Hz, 1H), 0.90
(s, 3H), 0.87 (s, 3H), 0.83 (s, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ 171.6, 79.9, 48.7, 47.8, 44.9, 36.8, 28.1, 27.1, 21.4, 19.8,
18.9, 13.6. IR (neat) 2955, 2881, 1737, 1455, 1362, 1247, 1113, 1034
cm−1. HRMS (EI) m/z: [M]+ calcd for C12H20O2 196.1463; found
196.1465.
Quinine Acetate (4s).42 Purified by silica gel column chromatog-
raphy (eluent: n-pentane/Et2O = 20:1−2:1). 730.2 mg, >99% yield [3
mol % 1aa, 21 h]. White solid. m.p. 114−117 °C (decomposition).
1H NMR (400 MHz, CDCl3) δ 8.75 (d, J = 4.6 Hz, 1H), 8.02 (d, J =
9.2 Hz, 1H), 7.43 (d, J = 2.3 Hz, 1H), 7.41−7.32 (m, 2H), 6.49 (d, J
= 7.3 Hz, 1H), 5.85 (ddd, J = 17.4, 10.1, 7.3 Hz, 1H), 5.07−4.97 (m,
2H), 3.96 (s, 3H), 3.38 (q, J = 8.2 Hz, 1H), 3.14−2.99 (m, 2H),
2.71−2.58 (m, 2H), 2.29 (m, 1H), 2.12 (s, 3H), 1.96−1.80 (m, 2H),
1.72 (m, 1H), 1.62−1.47 (m, 2H). 13C{1H} NMR (100 MHz,
CDCl3) δ 170.2, 157.9, 147.6, 144.9, 143.6, 141.8, 131.9, 127.1, 121.8,
119.0, 114.6, 101.5, 73.8, 59.1, 56.7, 55.7, 42.5, 39.8, 27.8, 27.6, 24.5,
21.2. IR (KBr) 2939, 2875, 1729, 1620, 1508, 1474, 1433, 1372, 1227,
1026 cm−1. HRMS (FAB+) m/z: [M + H]+ calcd for C22H27N2O3
367.2022; found 367.2026.
(Z)-Hex-4-enyl Isobutyrate (4m). Purified by silica gel column
chromatography (eluent: n-pentane/Et2O = 20:1−2:1). 340.7 mg,
1
>99% yield [3 mol % 1aa, 22 h]. Yellow oil. H NMR (400 MHz,
CDCl3) δ 5.50 (m, 1H), 5.37 (m, 1H), 4.07 (t, J = 6.4 Hz, 2H), 2.55
(septet, J = 6.9 Hz, 1H), 2.12 (q, J = 7.3 Hz, 2H), 1.69 (quintet, J =
6.8 Hz, 2H), 1.61 (d, J = 6.4 Hz, 3H), 1.17 (d, J = 6.9 Hz, 6H).
13C{1H} NMR (100 MHz, CDCl3) δ 177.3, 129.2, 125.0, 63.8, 34.1,
28.5, 23.2, 19.1 (2C), 12.8. IR (neat) 2974, 1737, 1470, 1259, 1192,
1158, 1078 cm−1. HRMS (DART+) m/z: [M + H]+ calcd for
C10H19O2 171.1385; found 171.1380.
3-(Trimethylsilyl)-2-propyn-1-yl 2-methylpropionate (4n). Puri-
fied by silica gel column chromatography (eluent: n-pentane/Et2O =
20:1−2:1). 377.7 mg, 95% yield [3 mol % 1aa, 3 h]; 371.6 mg, 94%
yield [1 mol % 1aa, 9 h]. Yellow oil. 1H NMR (400 MHz, CDCl3) δ
4.68 (s, 2H), 2.6 (septet, J = 6.9 Hz, 1H), 1.19 (d, J = 6.9 Hz, 6H),
0.18 (s, 9H). 13C{1H} NMR (100 MHz, CDCl3) δ 176.4, 99.3, 91.9,
(S)-(Methoxycarbonyl)(phenyl)methyl Isobutyrate (4t). Purified
by silica gel column chromatography (eluent: n-pentane/Et2O =
20:1−2:1). 472.5 mg, >99% yield, 98% ee [3 mol % 1aa, 3 h]. Yellow
1
oil. H NMR (400 MHz, CDCl3) δ 7.51−7.45 (m, 2H), 7.43−7.36
(m, 3H), 5.92 (s, 1H), 3.72 (s, 3H), 2.72 (septet, J = 6.9 Hz, 1H),
1.28 (d, J = 6.9 Hz, 3H), 1.22 (d, J = 6.9 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ 176.5, 169.5, 134.0, 129.2, 128.9 (2C), 127.6
(2C), 74.2, 52.7, 33.9, 19.0, 18.8. IR (neat) 2977, 1747, 1497, 1456,
1389, 1341, 1149, 1042 cm−1. HRMS (DART+) m/z: [M + H]+ calcd
for C13H17O4 237.1127; found 237.1126. The enantiomeric purity of
the product was determined by GC analysis: CHIRALDEX γ-TA, 110
5207
J. Org. Chem. 2021, 86, 5197−5212