´
E.G. Narvaez O et al.
Journal of Fluorine Chemistry 242 (2021) 109717
TLC). The organic phase was separated, dried (over Na2SO4) and the
solvent removed with a rotary evaporator.
Compound 5 is a reaction side product, isolated by column chro-
matography (Hexane/EtOAc, 9:1) during the purification of 4. The
stoichiometric detail is described in Fig. S15 of the supplementary
material.
4.3.1. 3-bromomethyl-6-chloro-2-trifluoromethyl chromone (3)
White crystalline solid (250 mg, 80 %) m.p. 97ꢀ 99 ◦C; UV (MeOH):
202, 209, 237, 318 nm; IR (KBr): 1649, 1606, 1173, 1149, 1033, 731,
680, 633 cmꢀ 1; 1H NMR (CDCl3, 300 MHz): δ 8.19 (d, J =2.5 Hz, H-5),
7.72 (dd, J =9 Hz and J =2.5 Hz, H-7), 7.52 (d, J =9 Hz, H-8), 4.53 (br.
quint, 5JH,F =1 Hz, CH2Br); 13C NMR (63 MHz, CDCl3) δ 174.5 (C-4),
153.3 (C-8a), 150.1 (q, J =38 Hz, C-2), 135.7 (C-7), 132.9 (C-6), 125.9
(C-5), 123.6 (C-4a), 121.4 (br. q. J =1 Hz, C-3), 120.2 (C-8), 119.9 (q, J
=277 Hz, CF3), 18.8 (q, J =3 Hz, CH2Br); 19F NMR (282 MHz, CDCl3) δ
-65.5 (s, CF3); GC–MS, 70 eV, m/z, (rel. int.): 342, (15), [M + 2]+; 340,
(11), [M]+; 261, (100), [M-79Br]+.; 226, (4), [M-79Br35Cl]+.
4.3.2. 3-bromomethyl-2-difluoromethyl chromone (4)
White solid (345 mg, 84 %); m.p. 112ꢀ 114 ◦C; UV (MeOH): 205,
235, 250, 303 nm; IR (KBr): 3022, 2922, 1649, 1609, 1432, 1056, 609
cmꢀ 1; 1H NMR (600 MHz, CDCl3) δ 8.24 (ddd, J = 8, 1.8 and 0.4 Hz, H-
5), 7.75 (ddd, J = 8.5, 7 and 1.5 Hz, H-7), 7.52 (ddd, J = 8.5, 1 and 0.4
Hz, H-8), 7.48 (ddd, J = 8, 7 and 1 Hz, H-6), 6.78 (t, 2JH,F =52.4 Hz,
CF2H), 4.57 (t, 5JH,F =1 Hz, CH2Br); 13C NMR (151 MHz, CDCl3) δ 175.7
(C-4), 155.4 (C-8a), 154.6 (t, 2JC,F =25 Hz, C-2), 135.1 (C-7), 126.44 (C-
5 or C-6), 126.41 (C-5 or C-6), 123.1 (C-4a), 121.3 (t, 3JC,F =2.5 Hz, C-3),
Fig. 3. View of the π⋅⋅⋅π stacking, showing the intercentroids distances for 5.
Table 4
Geometrical parameters for the π-stacking moieties involved in the π⋅⋅⋅π in-
teractions for 5 (Å, o).
Rings I
Cg(I)
⋯Cg
(J)b
Cg(I)
Cg(J)
αe
β f
γg
symmetry
- Ja
⋯Perp c
⋯Perp d
1
4
118.5 (C-8), 109.6 (t, JC,F =244 Hz, CF2H), 18.9 (t, JC,F =1.5 Hz,
CH2Br); 19F NMR (565 MHz, CDCl3) δ -120.58 (CF2H); GC–MS, 70 eV,
m/z, (rel. int.): 290, (13), [M+H]+; 288, (13), [M]+.; 209, (100), [M-
Br]+.
Cg
3.6511
(3)
3.4790
3.4790
3.4790
0.00
17.7
17.7
-x,-1/
(1)⋯
Cg
2+y,2-z
(2)
Cg(2)
⋯Cg
(2)
3.7977
(3)
3.4790
0.00
23.6
23.6
-x,-1/
2+y,2-z
4.3.3. 3-dibromomethyl-2-difluoromethyl chromone (5)
White solid (30 mg, 6%): UV (MeOH): 201, 216, 276, 340 nm; IR
(KBr): 3010, 2922, 1650, 1637, 1068, 646, 600 cmꢀ 1. GC–MS, 70 eV, m/
z, (rel. int.): 366, (7), [M]+; 368, (14), [M + 2]+.; 370, (7), [M + 4]+;
287, (100), [M-Br]+.
a
Cg(1) and Cg(2) are the centroids of pyrane and benzene rings, respectively.
Centroid distance between ring i and ring J.
b
c
d
e
f
Perpendicular distance of Cg(I) on ring J (Å).
Perpendicular distance of Cg(J) on ring I (Å).
Dihedral angle between planes I and J (Degrees).
4.3.4. 3-dibromomethyl-2-dichloromethyl chromone (6)
Angle between the centroid vector Cg(i)⋅⋅ ⋅Cg(j) and the normal to the plane
Yellow solid (23 mg, 20 %); m.p. 229–232 ◦C; UV (MeOH): 202, 241,
252, 306 nm; IR (KBr): 3040, 3010, 1647, 1625, 763, 633, 587 cmꢀ 1; 1H
NMR (600 MHz, CDCl3) δ 8.22 (dd, J = 8, 1.5 Hz, H-5), 7.79 (ddd, J =
8.5, 7 and 1.5 Hz, H-7), 7.71 (br. s., CHBr2), 7.62 (d, J =8.5 Hz, H-8),
7.49 (ddd, J = 8, 7 and 1 Hz, H-6), 7.39 (s, CHCl2); 13C NMR (151 MHz,
CDCl3) δ 155,62 (C-2); 135,44 (C-7); 126,76 (C-5); 126,56 (C-6); 122,37
(C-4a); 118,50 (C-8); 63,36 (CCl2H); 25,07 (CHBr2). GC–MS, 70 eV, m/z,
(rel. int.): 398, (1), [M]+; 400, (4), [M + 2]+.; 402, (3), [M + 4]+; 404,
(1), [M + 6]+; 321, (100), [M-Br]+.
(i).
g
Angle between the centroid vector Cg(i)⋅⋅ ⋅Cg(j) and the normal to the plane
(j).
thoroughly with water and then dried to constant weight in vacuum
(Scheme 2). The crude product was purified by column chromatography
(Hexane/EtOAc, 7:3) to give 158.5 mg (40 %) of 2 as a white crystalline
solid. UV (MeOH): 205, 224, 246, 252, 309 nm; IR (KBr): 1657, 1613,
1177, 1157, 725, 663, 607 cmꢀ 1; 1H NMR (300 MHz, CDCl3): δ 8.38 (dd,
J = 2.5 and 0.4 Hz, H-5), 7.89 (dd, J = 9 and 2.5 Hz, H-7), 7.48 (dd, J = 9
and 0.4 Hz, H-8); 13C NMR (151 MHz, CDCl3) δ 171.1 (C-4), 153.5 (C-
8a), 150.0 (q, J =38 Hz, C-2), 138.6 (C-7), 129.3 (C-5), 122.9 (C-4a or C-
6), 120.7 (C-4a or C-6), 120.3 (C-8), 118.9 (q, J =277 Hz, CF3), 111.0 (d,
J =1 Hz, C-3); 19F NMR (282 MHz, CDCl3) δ -66.29 (s, CF3); GC–MS, 70
eV, m/z, (rel. int.): 374, (50), [M + 4]+; 372, (100), [M + 2]+; 370, (50),
[M]+; 291, (3), [M-79Br]+.
4.3.5. 3-bromomethyl-2-pentafluoroethyl chromone (7)
White solid (412 mg, 80 %); m.p. 83–85 ◦C; UV (MeOH): 205, 228,
249, 306 nm; IR (KBr): 2852, 1657, 1630, 1435, 1204, 1164, 607 cmꢀ 1
;
1H NMR (600 MHz, CDCl3) δ 8.26 (ddd, J = 8, 1.5 and 0.5 Hz, H-5), 7.79
(ddd, J = 8.5, 7 and 1.5 Hz, H-7), 7.52 (ddd, J = 8.5, 1 and 0.5 Hz, H-8),
7.51 (ddd, J = 8, 7 and 1 Hz, H-6), 4.58 (t, 5JH,F =2 Hz, CH2Br); 13C NMR
(151 MHz, CDCl3) δ 175.3 (C-4), 155.2 (C-8a), 149.4 (t, 2JC,F =28 Hz, C-
2), 135.5 (C-7), 126.8 (C-5 or C-6), 126.8 (C-5 or C-6), 124.0 (C-4a),
122.6 (C-3), 118.5 (qt, J = 287, 35.5 Hz, CF2CF3), 118.4 (C-8), 18.94 (t,
4JC,F =5.5 Hz, CH2Br); 19F NMR (565 MHz, CDCl3) δ -116.07 (CF2)
-82.86 (CF3); GC–MS, 70 eV, m/z, (rel. int.): 356, (19), [M]+; 358, (18),
[M + 2]+.; 277, (100), [M-Br]+.
4.3. General procedure for bromination of 3-methyl-2-polyhaloalkyl
chromone (synthesis of 3-7)
In a bottom flask with ground glass joint, 3-methyl-2-polyhaloalkyl
chromone (1.5 mmol) was dissolved in 10 mL of carbon tetrachloride.
Then, 10 mL of aqueous saturated bromine solution was added, the
mixture was sealed with a rubber stopper and kept with stirring at room
temperature under visible light irradiation for 1–6 days (monitored by
4.4. X ray diffraction data and structural refinement of 5
The measurements were performed on an Oxford Xcalibur Gemini,
8