The Journal of Organic Chemistry
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silica gel chromatography (100% pentane) provided 1f (82 μmol, 22
mg, 82%) as a colorless solid. Rf 0.19 (100% hexanes); mp: 56−57 °C;
1H NMR (500 MHz, CDCl3): δ 7.29 (d, J = 8.1, 4H), 7.14 (d, J = 7.9,
4H), 5.25 (d, J = 1.3, 2H), 5.00 (s, 2H), 2.62 (s, 4H), 2.35 (s, 6H); 13C
NMR (125 MHz, CDCl3): δ 148.0, 138.3, 137.2, 129.1, 126.1, 111.8,
34.5, 21.3; IR (thin film): 3082, 3023, 2921, 2861, 1624, 1512, 1453
cm−1; HRMS-CI (m/z) [M + H]+ calculated for C20H22H 263.1800,
found 263.1804.
2,5-Bis(3-methylphenyl)hexa-1,5-diene (1g). Following the gen-
eral procedure, 1g was synthesized from Ru(bpy)3(PF6)2 (2.0 μmol, 2
mg, 1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0 equiv), i-
Pr2NEt (0.40 mmol, 63 μL, 2.0 equiv), and 3-methyl-α-
(bromomethyl)styrene (2g, 0.20 mmol, 42 mg, 1.0 equiv) in
CH2Cl2 (1.0 mL). Purification by silica gel chromatography (100%
pentane) provided 1g (88 μmol, 23 mg, 88%) as a colorless oil. Rf 0.36
(100% hexanes); 1H NMR (500 MHz, CDCl3): δ 7.24−7.18 (m, 6H),
7.10 (d, J = 6.9, 2H), 5.27 (d, J = 1.4, 2H), 5.04 (s, 2H), 2.63 (s, 4H),
2.36 (s, 6H); 13C NMR (125 MHz, CDCl3): δ 148.3, 141.2, 137.9,
128.3, 128.2, 127.0, 123.4, 112.5, 34.5, 21.7; IR (thin film): 3035,
2919, 2859, 2360, 1787, 1626, 1600, 1575, 1486, 1452 cm−1; HRMS-
CI (m/z) [M + H]+ calculated for C20H22H 263.1800, found
263.1792.
2,5-Bis(2-methylphenyl)hexa-1,5-diene (1h). Following the gen-
eral procedure, 1h was synthesized from Ru(bpy)3(PF6)2 (2.0 μmol, 2
mg, 1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0 equiv), i-
Pr2NEt (0.40 mmol, 63 μL, 2.0 equiv), and 2-methyl-α-
(bromomethyl)styrene (2h, 0.20 mmol, 42 mg, 1.0 equiv) in
CH2Cl2 (0.5 mL). Purification by silica gel chromatography (100%
pentane) provided 1h (72 μmol, 19 mg, 72%) as a colorless oil.
Under the same conditions, coupling product 1h (90 mg, 69%) was
obtained from Ru(bpy)3(PF6)2 (0.01 mmol, 8.5 mg, 1 mol %),
Hantzsch ester 3 (1.00 mmol, 255 mg, 1.0 equiv), i-Pr2NEt (2.00
mmol, 0.32 mL, 2.0 equiv), and 2-methyl-α-(bromomethyl)styrene
(2h, 1.00 mmol, 210 mg, 1.0 equiv) in CH2Cl2 (2.5 mL).
equiv), i-Pr2NEt (0.40 mmol, 63 μL, 2.0 equiv), and 2-methoxy-α-
(bromomethyl)styrene (2k, 0.20 mmol, 45 mg, 1.0 equiv) in CH2Cl2
(0.5 mL). The reaction time was extended from 18 to 42 h.
Purification by silica gel chromatography (5% diethyl ether/hexanes)
provided 1k (69 μmol, 20 mg, 69%) as a colorless solid. Rf 0.44 (5%
ethyl acetate/hexanes); mp: 98−100 °C; 1H NMR (500 MHz,
CDCl3): δ 7.26−7.22 (m, 2H), 7.10 (dd, J = 7.4, 1.7, 2H), 6.90 (dt, J =
7.4, 1.0, 2H), 6.85 (d, J = 8.2, 2H), 5.12 (s, 2H), 5.00 (d, J = 2.0, 2H),
3.75 (s, 6H), 2.55 (s, 4H); 13C NMR (125 MHz, CDCl3): δ 156.6,
148.9, 132.2, 130.4, 128.4, 120.5, 114.2, 110.7, 55.5, 35.0; IR (thin
film): 3072, 2944, 2837, 1633, 1597, 1489, 1458, 1435, 1239, 1024
cm−1; HRMS-CI (m/z) [M]+ calculated for C20H22O2 294.1620,
found 294.1625.
2,5-Bis(4-cyanophenyl)hexa-1,5-diene (1l). Following the general
procedure, 1l was synthesized from Ru(bpy)3(PF6)2 (2.0 μmol, 2 mg,
1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0 equiv), i-Pr2NEt
(0.40 mmol, 63 μL, 2.0 equiv), and 4-cyano-α-(bromomethyl)styrene
(2l, 0.20 mmol, 44 mg, 1.0 equiv) in CH2Cl2 (0.5 mL). Purification by
silica gel chromatography (10% → 20% diethyl ether/hexanes)
provided 1l (73 μmol, 21 mg, 73%) as a colorless solid. Rf 0.18
(10% ethyl acetate/hexanes); mp: 115−116 °C; 1H NMR (500 MHz,
CDCl3): δ 7.62 (d, J = 8.4, 4H), 7.44 (d, J = 8.4, 4H), 5.37 (s, 2H),
5.15 (s, 2H), 2.63 (s, 4H); 13C NMR (125 MHz, CDCl3): δ 146.1,
145.5, 132.4, 126.9, 118.9, 116.1, 111.2, 33.6; IR (thin film): 3065,
2917, 2852, 2360, 2341, 2226, 1623, 1604, 1504, 1401, 1128 cm−1;
HRMS-ESI (m/z) [M + Na]+ calculated for C20H16N2Na 307.1211,
found 307.1213.
2,5-Bis(3-cyanophenyl)hexa-1,5-diene (1m). Following the general
procedure, 1m was synthesized from Ru(bpy)3(PF6)2 (2.0 μmol, 2 mg,
1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0 equiv), i-Pr2NEt
(0.40 mmol, 63 μL, 2.0 equiv), and 3-cyano-α-(bromomethyl)styrene
(2m, 0.20 mmol, 44 mg, 1.0 equiv) in CH2Cl2 (1.0 mL). Purification
by silica gel chromatography (20% diethyl ether/hexanes) provided
1m (74 μmol, 21 mg, 74%) as a colorless solid. Rf 0.51 (20% ethyl
1
Rf 0.39 (100% hexanes); 1H NMR (500 MHz, CDCl3): δ 7.18−7.11
(m, 6H), 7.06 (d, J = 6.9, 2H), 5.20 (s, 2H), 4.89 (d, J = 1.9, 2H), 2.45
(s, 4H), 2.26 (s, 6H); 13C NMR (125 MHz, CDCl3): δ 149.6, 143.0,
134.9, 130.2, 128.5, 126.9, 125.5, 114.1, 35.9, 20.0; IR (thin film):
3070, 3016, 2924, 2360, 1634, 1487, 1452, 1211, 1045 cm−1; HRMS-
CI (m/z) [M + H]+ calculated for C20H22H 263.1800, found
263.1804.
acetate/hexanes); mp: 64−65 °C; H NMR (500 MHz, CDCl3): δ
7.61−7.59 (m, 2H), 7.58−7.55 (m, 4H), 7.46−7.42 (m, 2H), 5.32 (s,
2H), 5.12 (s, 2H), 2.61 (s, 4H); 13C NMR (125 MHz, CDCl3): δ
145.6, 142.2, 131.1, 130.6, 129.9, 129.4, 118.9, 115.4, 112.7, 33.6; IR
(thin film): 3082, 2921, 2851, 2360, 2229, 1627, 1574, 1480 cm−1;
HRMS-ESI (m/z) [M + Na]+ calculated for C20H16N2Na 307.1211,
found 307.1224.
Wurtz-Type Coupling of (Z)-(1-Bromobut-2-en-2-yl)benzene (4).
Following the general procedure, the reaction of Ru(bpy)3(PF6)2 (2.0
μmol, 2 mg, 1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0
equiv), i-Pr2NEt (0.40 mmol, 63 μL, 2.0 equiv), and (Z)-(1-bromobut-
2-en-2-yl)benzene (4, 0.20 mmol, 42 mg, 1.0 equiv) in CH2Cl2 (0.5
mL) gave a crude product. Purification by silica gel chromatography
(100% pentane) provided a mixture of the three regioisomers 6 (36
μmol, 10 mg, 36%), 7 (43 μmol, 11 mg, 43%), and 8 (15 μmol, 4 mg,
15%). Analytical samples were obtained by an automated flash
chromatography system.
2,5-Bis(4-methoxyphenyl)hexa-1,5-diene (1i). Following the gen-
eral procedure, 1i was synthesized from Ru(bpy)3(PF6)2 (2.0 μmol, 2
mg, 1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0 equiv), i-
Pr2NEt (0.40 mmol, 63 μL, 2.0 equiv), and 4-methoxy-α-
(bromomethyl)styrene (2i, 0.20 mmol, 45 mg, 1.0 equiv) in CH2Cl2
(0.5 mL). Purification by silica gel chromatography (5% diethyl ether/
hexanes) provided 1i (63 μmol, 19 mg, 63%) as a colorless solid. Rf
1
0.45 (10% ethyl acetate/hexanes); H NMR (500 MHz, CDCl3): δ
7.35 (d, J = 8.5, 4H), 6.87 (d, J = 8.4, 4H), 5.22 (s, 2H), 4.97 (s, 2H),
3.82 (s, 6H), 2.62 (s, 4H); 13C NMR (125 MHz, CDCl3): δ 159.2,
147.5, 133.6, 127.3, 113.7, 111.1, 55.4, 34.5. Characterization data
obtained for 1i matched those previously reported in the literature.14b
2,5-Bis(3-methoxyphenyl)hexa-1,5-diene (1j). Following the gen-
eral procedure, 1j was synthesized from Ru(bpy)3(PF6)2 (2.0 μmol, 2
mg, 1 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0 equiv), i-
Pr2NEt (0.40 mmol, 63 μL, 2.0 equiv), and 3-methoxy-α-
(bromomethyl)styrene (2j, 0.20 mmol, 45 mg, 1.0 equiv) in CH2Cl2
(0.5 mL). Purification by silica gel chromatography (5% diethyl ether/
hexanes) provided 1j (74 μmol, 22 mg, 74%) as a colorless oil. Rf 0.50
Data for 6: colorless solid; Rf 0.45 (100% hexanes); 1H NMR (500
MHz, CDCl3): δ 7.31−7.28 (m, 8H), 7.24−7.20 (m, 2H), 5.72 (q, J =
6.9, 2H), 2.54 (s, 4H), 1.67 (d, J = 6.9, 6H); 13C NMR (125 MHz,
CDCl3): δ 143.1, 140.5, 128.3, 126.6, 126.4, 123.4, 28.1, 14.2.
Characterization data obtained for 6 matched those previously
reported in the literature.34
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Data for 7: colorless oil; Rf 0.50 (100% hexanes); H NMR (500
MHz, CDCl3): δ 7.30−7.19 (m, 10H), 5.75 (q, J = 6.8, 1H), 5.17 (d, J
= 0.9, 1H), 5.08−5.07 (m, 1H), 2.70−2.64 (m, 2H), 2.50−2.45 (m,
1H), 1.77 (d, J = 6.9, 3H), 1.07 (d, J = 6.9, 3H); 13C NMR (125 MHz,
CDCl3): δ 155.1, 143.3, 142.9, 140.1, 128.3, 128.2, 127.3, 126.9, 126.7,
126.6, 124.6, 111.0, 36.4, 35.7, 18.6, 14.6; IR (thin film): 3022, 3961,
2925, 2360, 1493, 1442, 1371, 1028 cm−1; HRMS-CI (m/z) [M + H]+
calculated for C20H22H 263.1800, found 263.1797.
Data for 8 (1:1 mixture of diastereomers): colorless oil; Rf 0.53
(100% hexanes); 1H NMR (500 MHz, CDCl3, mixture of
diastereomers): δ 7.34−7.24 (m, 16H), 7.20−7.16 (m, 4H), 5.20−
5.19 (m, 2H), 5.19 (s, 2H), 5.06 (s, 2H), 5.01−5.00 (m, 2H), 2.79−
2.72 (m, 4H), 1.18 (d, J = 6.2, 6H), 0.94 (d, J = 6.8, 6H).
1
(10% ethyl acetate/hexanes); H NMR (500 MHz, CDCl3): δ 7.27−
7.23 (m, 2H), 6.99 (d, J = 7.8, 2H), 6.94−6.92 (m, 2H), 6.83 (dd, J =
8.2, 2.5, 2H), 5.29 (d, J = 1.2, 1H), 5.06 (s, 2H), 3.82 (s, 6H), 2.64 (s,
4H); 13C NMR (125 MHz, CDCl3): δ 159.7, 148.1, 142.8, 129.4,
118.6, 112.9, 112.8, 112.2, 55.3, 34.5; IR (thin film): 3078, 2934, 2833,
1602, 1575, 1487, 1460, 1427, 1286, 1231, 1047 cm−1; HRMS-CI (m/
z) [M + H]+ calculated for C20H22O2H 295.1698, found 295.1700.
2,5-Bis(2-methoxyphenyl)hexa-1,5-diene (1k). Following the
general procedure, 1k was synthesized from Ru(bpy)3(PF6)2 (3.0
μmol, 3 mg, 1.5 mol %), Hantzsch ester 3 (0.20 mmol, 51 mg, 1.0
H
J. Org. Chem. XXXX, XXX, XXX−XXX