Vol. 32, No. 7 (2020)
CuSCN Catalyzed Conjugate Addition of Grignard Reagents to Substituted Coumarins 1795
1H), 4.76 (t, J = 7 Hz, 1H), 3.05 (d, J = 7 Hz, 2H), 13C NMR
(125 MHz, CDCl3) δ ppm: 55.54, 155.98, 114.24, 116.71,
144.67, 125.87, 110.78, 38.96, 38.17, 168.60, 127.81, 143.13,
112.38, 142.73. Anal. calcd. (found) %:, C, 68.85 (68.83), H,
4.95 (4.96), O, 26.20 (26.21).
(found) %: C, 72.39 (72.41), H, 6.94 (6.93), O, 20.66 (20.65).
6-Methoxy-4-phenyl-4-(trifluoromethyl)-3,4-dihydro-
2H-chromen-2-one (2i): Pale yellow liquid, m.f. C17H13O3F3,
IR (KBr, νmax, cm-1): 1745, 1100, 1600, 2900, 950, 1H NMR
(500 MHz, CDCl3) δ ppm: 7.28 (m, J = 8, 2.5 & 1 Hz, 5H),
3.07 (s, 2 H), 3.75 (s, 3H), 6.70 (d, J = 2.5 Hz, 1H), 6.76 (dd,
J = 8, 2.5 Hz, 1H), 7.01 (d, J = 8 Hz, 1H), 13C NMR (125
MHz, CDCl3) δ ppm: 55.46, 156.90, 115.69, 117.59, 149.03,
128, 113.20, 47.22, 39.66, 168.11, 125.90, 140.17, 127.68,
128.29, 126.25, Anal. calcd. (found) %: C, 63.36 (63.37), H,
4.07 (4.06), O, 14.89 (14.88), F, 17.69 (17.70).
6-Methoxy-4-(prop-2-en-1-yl)-3,4-dihydro-2H-chromen-
2-one (2d): Colourless liquid, m.f.: C13H14O3, IR (KBr, νmax
,
cm-1): 1745, 1600, 1100, 3100, 1H NMR (500 MHz, CDCl3) δ
ppm: 3.75 (s, 3H), 6.84 (d, J = 8 Hz, 1H), 6.76 (dd, J = 8 & 2.5
Hz, 1H), 7.01 (d, J = 8 Hz, 1H), 3.70 (m, J = 7 Hz, 1H), 3.04 (d,
J = 7 Hz, 2H), 2.28 (t, J = 7 Hz, 2H), 5.75 (m, J = 10 & 15 Hz,
1H), 4.99 (d, J = 10 & 15 Hz, 2H), 13C NMR (125 MHz, CDCl3)
δ ppm: 55.54, 155.37, 113.80, 116.40, 148.13, 126.08, 110.14,
31.70, 35.49, 168.86, 36.03, 135.10, 117.14.Anal. calcd. (found)
%: C, 71.54 (71.56), H, 6.47 (6.46), O, 21.99 (21.98).
6-Methoxy-4-methyl-4-phenyl-3,4-dihydro-2H-
chromen-2-one (2e): Colourless liquid, m.f.: C17H16O3, IR
(KBr, νmax, cm-1): 1745, 1600, 1100, 2900, 1H NMR, (500 MHz,
CDCl3) δ ppm: 7.26 (m, J = 8, 2.5 &1 Hz, 5H), 1.63 (s, 3H),
3.05 (s, 2H), 3.75 (s, 3H), 6.70 (d, J = 2.5 Hz, 1H), 6.76 (dd, J
= 8, 2.5 Hz, 1H), 7.01 (d, J = 8 Hz, 1H), 13C NMR (125 MHz,
CDCl3) δ ppm: 55.46, 157.55, 114.60, 117.36, 148.83, 134.22,
111.36, 37.44, 43.82, 168.14, 148.15, 127.02, 128.62, 126.90.
Anal. calcd. (found) %: C, 76.10 (76.12), H, 6.01 (6.00), O,
17.89 (17.88).
6-Methoxy-4-(pyridin-2-yl)-4-(trifluoromethyl)-3,4-
dihydro-2H-chromen-2-one (2j): Yellow liquid, m.f.
C16H12NO3F3, IR (KBr, νmax, cm-1): 1745, 1600, 1100, 1660,
950, 2900, 1H NMR (500 MHz, CDCl3) δ ppm:, 7.41 (m, J=
8.5, 2.7 & 1.2 Hz, 1 H), 7.54 (m, J = 8.5 & 2.7 Hz, 1H), 7.10
(m, J = 8.5 & 2.7 Hz, 1H), 8.51 (m, J = 8.5, 2.7 & 1.2 Hz, 1H),
3.04 (s, 2H) , 3.75 (s, 3H), 6.70 (d, J = 8 Hz, 1H), 6.76 (dd, J
13
= 8 & 2.5 Hz, 1H), 7.01 (d, J = 8 Hz, 1H), C NMR (125
MHz, CDCl3) δ ppm: 55.46, 157.46, 117.12, 118.68, 149.18,
128.64, 114.13, 45.49, 123.39, 39.86, 168.11, 160.12, 124.17,
137.11, 122.07, 147.88. Anal. calcd. (found) %: C, 59.45
(59.44), H, 3.74 (3.75), O, 14.85 (14.84), F, 17.63 (17.64).
4-(Furan-3-yl)-6-methoxy-4-(trifluoromethyl)-3,4-
dihydro-2H-chromen-2-one (2k): Yellow liquid, m.f.:
C15H11O4F3, IR IR (KBr, νmax, cm-1): 1745, 1100, 950, 2900,
1H NMR (500 MHz, CDCl3) δ ppm: 7.43 (dd, J= 7.5 & 1.5
Hz, 1H), 6.39 (dd, J= 7.5 & 1.5 Hz, 1H), 7.39 (dd, J = 7.5 &
1.5 Hz, 1H), 3.75 (s, 3H), 6.70 (d, J = 8 Hz, 1H), 6.76 (dd, J =
8 & 2.5 Hz, 1H), 7.01 (d, J = 8 Hz, 1H), 3.05 (s, 2H), 13C NMR
(125 MHz, CDCl3) δ ppm: 55.46, 156.91, 116.07, 118.78,
149.51, 123.19, 114.75, 125.55, 54.84, 37.08, 167.63, 90,
114.85, 144.35, 136.Anal. calcd. (found) %: C, 57.70 (57.71),
H, 3.55 (3.54) O, 20.50 (20.51), F, 18.25 (18.24).
6-Methoxy-4-(prop-2-en-1-yl)-4-(trifluoromethyl)-3,4-
dihydro-2H-chromen-2-one (2l) Pale yellow liquid, m.f.:
C14H13O3F3, IR (KBr, νmax, cm-1): 1745, 1600, 1100, 3100, 950,
1H NMR (500 MHz, CDCl3) δ ppm: 3.75 (s, 3H), 6.89 (d, J =
2 Hz, 1H), 6.66 (dd, J = 8 & 2 Hz, 1H), 6.94 (d, J = 8 Hz, 1H),
2.65 (s, 2H), 2.16 (d, J = 7 Hz, 2H), 5.75 (m, J = 15 & 9 Hz,
1H), 4.99 (d, J = 9, 15 & 2.5 Hz, 2H), 13C NMR (125 MHz,
CDCl3) δ ppm: 55.46, 156.54, 114.82, 118.53, 150.82, 123.30,
41.83, 113.39, 37.55, 169.44, 37.99, 134.09, 118.60, 121.86.
Anal. calcd. (found) %: C, 58.74 (58.75), H, 4.58 (4.57), O,
16.77 (16.78), F, 19.91 (19.90).
6-Methoxy-4-methyl-4-(pyridin-2-yl)-3,4-dihydro-2H-
chromen-2-one (2f): Yellow liquid, m.f.: C16H15NO3, IR (KBr,
ν
max, cm-1): 1745, 1600, 1100, 2900, 1660, 1H NMR (500 MHz,
CDCl3) δ ppm: 7.41 (m, J = 8.5, 2.7 & 1.2 Hz, 1H), 7.54 (m, J
= 8.5 & 2.7 Hz, 1H), 7.10 (m, J = 8.5 & 2.7 Hz, 1H), 8.51 (m,
J = 8.5, 2.7 & 1.2 Hz, 1H), 1.63 (s, J = 7 Hz, 3H), 3.04 (s, 2H),
3.75 (s, 3H), 6.70 (d, J = 8 Hz, 1H), 6.76 (dd, J = 8 & 2.5 Hz,
1H), 7.01 (d, J = 8 Hz, 1H), 13C NMR (125 MHz, CDCl3) δ
ppm: 55.46, 157.46, 113.42, 118.0, 149.85, 137.50, 111.35,
25.04, 37.55, 46.86, 168.14, 169.21, 120.18, 138.36, 121.67,
149.04. Anal. calcd. (found) %: C, 71.36 (71.37), H, 5.61
(5.60), N, 5.20 (5.19), O, 17.82 (17.83).
4-(Furan-3-yl)-6-methoxy-4-methyl-3,4-dihydro-2H-
chromen-2-one (2g): Yellow liquid, m.f.: C15H14O4, IR (KBr,
1
ν
max, cm-1): 1745, 1600, 1100, 2900, H NMR (500 MHz,
CDCl3) δ ppm: 7.43 (dd, J = 7.5 & 1.5 Hz, 1H), 6.39 (dd, J=
7.5 & 1.5 Hz, 1H), 7.39 (dd, J = 7.5 & 1.5 Hz, 1H), 3.75 (s,
3H), 6.70 (d, J = 8 Hz, 1H), 6.76 (dd, J = 8 & 2.5 Hz, 1H),
7.01 (d, J = 8 Hz, 1H), 1.63 (s, 3H), 3.05 (s, 2H), 13C NMR
(125 MHz, CDCl3) δ ppm: 55.46, 157.44, 113.75, 117.77,
148.84, 132.15, 111.67, 25.63, 35.74, 42.89, 167.47, 140.56,
110.66, 141.91, 136.92. Anal. calcd. (found) %: C, 69.76
(69.74), H, 5.46 (5.47), O, 24.78 (24.79).
RESULTS AND DISCUSSION
To account for the significance of solvent in this process,
the reactions were carried out in the absence of Li2MnCl4 in
which reaction requires a longer time and lower yields. How-
ever, the reaction was carried out in the presence of Li2MnCl4
and different solvents like THF, diethyl ether, and 1,4-dioxane
wherein the reaction it gives different yields and high regio-
selectivity (Table-1). Table-2 shows the results obtained from
using different reaction parameters for the synthesis of
compounds 2a to 2l. It has also been observed that substituted
coumarin gives results with Grignard reagents in the presence
6-Methoxy-4-methyl-4-(prop-2-en-1-yl)-3,4-dihydro-
2H-chromen-2-one (2h): Colourless liquid, m.f.: C14H16O3,
IR (KBr, νmax, cm-1): 1745, 1600, 1100, 3100, 1H NMR (500
MHz, CDCl3) δ ppm: 3.75 (s, 3H), 6.89 (d, J = 2 Hz, 1H), 6.66
(dd, J = 8 & 2 Hz, 1H), 6.94 (d, J = 8 Hz, 1H), 3.05 (s, 2H),
1.49 (s, 3H), 2.16 (d, 2H), 5.75 (m, J = 15 & 9 Hz, 1H), 4.99
13
(d, J= 9, 15 & 2.5 Hz, 2H), C NMR (125 MHz, CDCl3) δ
ppm: 55.46, 157.88, 115.82, 118.53, 147.82, 133.80, 109.48,
37.55, 43.63, 167.88, 45.77, 133.59, 118.89, 25.8.Anal. calcd.