3.1.3. 6,8-Diiodo-2-(4-ethylphenyl)-4-oxochroman-3-yl *N*,*N*-diethyldithiocarbamate (**4b**)

Colourless crystals, 0.22 g, 68%. IR (ATR, cm<sup>−</sup>1) 2965, 1697, 1417, 1256, 1202, 825, 641, 474, 438. 1H NMR (CDCl3, selected data for the major isomer) δ 8.26 (d, *J* = 1.8 Hz, 1H), 8.13

(d, *J* = 1.8 Hz, 1H), 7.4 (d, *J* = 7.9 Hz, 2H), 7.19 (d, *J* = 7.9 Hz, 2H), 6.01 (d, *J* = 6.3 Hz, 1H), 5.76 (d, *J* = 6.3 Hz, 1H), 3.98 (m, 2H), 3.69 (m, 2H), 2.65 (q, *J* = 7.5 Hz, 2H), 1.25 (t, *J* = 7.5 Hz, 3H), 1.23 (t, *J* = 7.6 Hz, 6H). 13C NMR (CDCl3, selected data for the major isomer) δ 191.2, 186.3, 158.8, 152.6, 144.9, 136.3, 133.0, 128.1, 127.2, 122.9, 87.6, 84.7, 83.0, 57.8, 50.5, 47.3, 28.5, 15.3, 12.6, 11.4. UV–vis (λmax, nm) 313. MS (EI) *m*/*z*: 650.8 (M+, 27%) for C22H23I2NO2S2.

3.1.4. 6,8-Diiodo-2-(4-fluorophenyl)-4-oxochroman-3-yl *N*,*N*-diethyldithiocarbamate (**4c**)

Colourless crystals, 0.24 g, 75%. IR (ATR, cm<sup>−</sup>1) 2980, 1685, 1419, 1226, 1201, 974, 825, 537, 474. 1H NMR (CDCl3, selected data for the major isomer) δ 8.27 (d, *J* = 1.9 Hz, 1H), 8.16 (d, *J* = 1.9 Hz, 1H), 7.49 (m, 2H), 7.06 (m, 2H), 5.96 (d, *J* = 7.3 Hz, 1H), 5.79 (d, *J* = 7.3 Hz, 1H), 3.95 (m, 2H), 3.71 (m, 2H), 1.24 (t, *J* = 6.8 Hz, 6H). 13C NMR (CDCl3, selected data for the major isomer) δ 190.9, 186.1, 162.9, 158.7, 152.7, 136.4, 131.7, 129.4, 122.4, 115.5, 87.4, 84.9, 82.6, 58.4, 50.7, 47.3, 12.6, 11.4. UV–vis (λmax, nm) 308. MS (EI) *m*/*z*: 640.8 (M+, 24%) for C20H18FI2NO2S2.

3.1.5. 6,8-Diiodo-2-(4-bromophenyl)-4-oxochroman-3-yl *N*,*N*-diethyldithiocarbamate (**4d**)

Colourless crystals, 0.28 g, 80%. IR (ATR, cm<sup>−</sup>1) 2977, 1700, 1421, 1252, 1201, 817, 507, 433, 417. 1H NMR (CDCl3, selected data for the major isomer) δ 8.28 (d, *J* = 1.9 Hz, 1H), 8.16 (d, *J* = 1.9 Hz, 1H), 7.52 (d, *J* = 8.2 Hz, 2H), 7.41 (d, *J* = 8.2 Hz, 2H), 5.95 (d, *J* = 7.1 Hz, 1H), 5.74 (d, *J* = 7.1, 1H), 3.92 (m, 2H), 3.66 (m, 2H), 1.24 (t, *J* = 6.7 Hz, 6H). 13C NMR (CDCl3, selected data for the major isomer) δ 190.8, 185.9, 158.7, 152.7, 136.5, 134.8, 131.7, 129.1, 123.1, 122.1, 87.4, 85.1, 82.6, 58.2, 50.7, 47.4, 12.6, 11.4. UV–vis (λmax, nm) 311. MS (EI) *m*/*z*: 700.7 (M+, 296%) for C20H18BrI2NO2S2.

3.1.6. 6,8-Diiodo-2-(4-methoxyphenyl)-4-oxochroman-3-yl *N*,*N*-diethyldithiocarbamate (**4e**)

Colourless crystals, 0.25 g, 77%. IR (ATR, cm<sup>−</sup>1) 1699, 1496, 1420, 1246, 1180, 1032, 828, 663. 1H NMR (CDCl3, selected data for the major isomer) δ 8.26 (m, 1H), 8.14 (m, 1H), 7.42 (d, *J* = 8.2 Hz, 2H), 6.89 (d, *J* = 8.2 Hz, 2H), 5.96 (d, *J* = 6.7 Hz, 1H), 5.78 (d, *J* = 6.7 Hz, 1H), 3.97 (m, 2H), 3.81 (s, 3H), 3.65 (m, 2H), 1.25 (t, *J* = 6.7 Hz, 6H). 13C NMR (CDCl3, selected data for the major isomer) δ 191.2, 186.4, 159.9, 158.8, 152.6, 136.4, 128.7, 127.9, 122.8, 113.9, 87.7, 87.6, 84.7, 58.1, 55.3, 50.5, 47.3, 12.6, 11.4. UV–vis (λmax, nm) 315. MS (EI) *m*/*z*: 652.8 (M+, 37%) for C21H21I2NO3S2.

3.1.7. General Procedure for 2-*N*,*N*-diethylamino-6,8-diiodo-4-(4-methylphenyl)-*4H*-1,3 dithiol[4,5-*c*]chromen-2-ylium tetrafluoroborate (**5a**)

To a mixture of sulfuric acid (1 mL) and acetic acid (1 mL), flavanone **4a** (0.21 g, 0.33 mmol) was added and the resulting solution was heated to 40 ◦C for 30 min. The reaction mixture was then left to cool to room temperature and a solution of sodium tetrafluoroborate (0.2 g) in water (10 mL) was added dropwise, with vigorous stirring. The resulting precipitate was then filtered, washed thoroughly with water and recrystallized from ethanol, yielding the desired tetrafluoroborate **5a** in the form of colourless crystals (0.17 g, 85%). M.p. 260–261 ◦C. IR (ATR, cm−1) 1554, 1438, 1224, 1045, 729, 494, 458. 1H NMR (DMSO-*d*6) δ 8.04 (d, *J* = 1.8 Hz, 1H), 7.74 (d, *J* = 1.8 Hz, 1H), 7.37 (d, *J* = 8.0 Hz, 2H), 7.26 (d, *J* = 8.0 Hz, 2H), 6.89 (s, 1H), 3.89 (m, 4H), 2.31 (s, 3H), 1.40 (t, *J* = 7.1 Hz, 3H), 1.32 (t, *J* = 7.1 Hz, 3H). 13C NMR (DMSO-*d*6) δ 184.9, 150.7, 147.8, 140.2, 133.8, 130.0, 129.7, 127.8, 126.8, 119.1, 88.7, 87.6, 76.2, 54.7, 54.6, 21.3, 10.8, 10.5. UV–vis (λmax, nm) 343. MS (EI) *m*/*z*: 619.9 (M+-BF4, 7%) for C21H20I2NOS2] +.

3.1.8. 2-*N*,*N*-Diethylamino-6,8-diiodo-4-(4-ethylphenyl)-*4H*-1,3-dithiol[4,5-*c*]chromen-2-ylium tetrafluoroborate (**5b**)

Colourless crystals, M.p. 201–202 ◦C, (0.17 g, 81%). IR (ATR, cm−1) 1549, 1428, 1217, 1034, 719, 496, 448. 1H NMR (DMSO-*d*6) δ 8.06 (d, *J* = 1.8 Hz, 1H), 7.73 (d, *J* = 1.8 Hz, 1H), 7.35 (d, *J* = 8.1 Hz, 2H), 7.24 (d, *J* = 8.1 Hz, 2H), 6.87 (s, 1H), 3.87 (m, 4H), 2.35 (q, *J* = 7.3 Hz, 2H), 1.40 (t, *J* = 7.1 Hz, 3H), 1.32 (t, *J* = 7.1 Hz, 3H), 1.26 (t, *J* = 7.3 Hz, 3H). 13C NMR

(DMSO-*d*6) δ 185, 150.5, 147.7, 140.1, 133.5, 129.9, 129.6, 127.5, 126.7, 119.0, 88.8, 87.5, 76.1, 54.8, 54.6, 25.4, 12.3, 10.7, 10.4. UV–vis (λmax, nm) 344. MS (EI) *m*/*z*: 633.9 (M+-BF4, 5%) for C22H22I2NOS2] +.

3.1.9. 2-*N*,*N*-diethylamino-6,8-diiodo-4-(4-fluorophenyl)-*4H*-1,3-dithiol[4,5-*c*]chromen-2-ylium tetrafluoroborate (**5c**)

Colourless crystals, M.p. 237–238 ◦C (0.17 g, 83%). IR (ATR, cm−1) 1551, 1433, 1225, 1048, 685, 458, 409. 1H NMR (DMSO-*d*6) δ 8.09 (d, *J* = 1.8 Hz, 1H), 7.80 (d, *J* = 1.8 Hz, 1H), 7.55 (dd, <sup>3</sup>*J*H-H = 8.7 Hz, <sup>4</sup>*J*H-F = 5.3 Hz, 2H), 7.30 (dd, <sup>3</sup>*J*H-H = 8.8 Hz, <sup>3</sup>*J*H-F = 8.7 Hz, 2H), 6.96 (s, 1H), 3.90 (m, 4H), 1.40 (t, *J* = 7.1 Hz, 3H), 1.33 (t, *J* = 7.1 Hz, 3H). 13C NMR (DMSO-*d*6) δ 185.0, 164.2, 162.3, 150.4, 147.8, 133.0, 130.3, 129.2, 127.1, 119.0, 116.5, 88.7, 87.7, 75.5, 54.7, 54.6, 10.8, 10.5. UV–vis (λmax, nm) 339. MS (EI) *m*/*z*: 623.8 (M+-BF4, 8%) for C20H17FI2NOS2] +.

3.1.10. 2-*N*,*N*-diethylamino-6,8-diiodo-4-(4-bromophenyl)-*4H*-1,3-dithiol[4,5-*c*]chromen-2-ylium tetrafluoroborate (**5d**)

Colourless crystals, M.p. 219–220 ◦C (0.2 g, 88%). IR (ATR, cm−1) 1546, 1429, 1225, 1049, 737, 441, 428. 1H NMR (DMSO-*d*6) δ 8.09 (d, *J* = 1.7 Hz, 1H), 7.79 (d, *J* = 1.7 Hz, 1H), 7.66 (d, *J* = 8.4 Hz, 2H), 7.43 (d, *J* = 8.4 Hz, 2H), 6.92 (s, 1H), 3.87 (m, 4H), 1.39 (t, *J* = 7.1 Hz, 3H), 1.32 (t, *J* = 7.1 Hz, 3H). 13C NMR (DMSO-*d*6) δ 185.0, 150.4, 147.9, 136.0, 133.1, 132.5, 130.0, 128.7, 127.2, 123.9, 119.0, 88.6, 87.8, 75.5, 54.7, 54.6, 10.7, 10.5. UV–vis (λmax, nm) 341. MS (EI) *m*/*z*: 683.7 (M+-BF4, 5%) for C20H17BrI2NOS2] +.

3.1.11. 2-*N*,*N*-diethylamino-6,8-diiodo-4-(4-methoxyphenyl)-*4H*-1,3-dithiol chromen-2-ylium tetrafluoroborate (**5e**)

Colourless crystals, M.p. 235–236 ◦C (0.17 g, 80%). IR (ATR, cm−1) 1548, 1429, 1247, 1070, 851, 617. 1H NMR (DMSO-*d*6) δ 8.08 (d, *J* = 1.8 Hz, 1H), 7.78 (d, *J* = 1.8 Hz, 1H), 7.41 (d, *J* = 8.7 Hz, 2H), 6.99 (d, *J* = 8.7 Hz, 2H), 6.86 (s, 1H), 3.90 (m, 4H), 3.76 (s, 3H), 1.40 (t, *J* = 7.1 Hz, 3H), 1.32 (t, *J* = 7.1 Hz, 3H). 13C NMR (DMSO-*d*6) δ 184.9, 160.9, 150.7, 147.7, 132.9, 129.9, 129.6, 128.6, 126.7, 119.0, 114.8, 88.7, 87.4, 76.1, 55.7, 54.7, 54.6, 10.8, 10.5. UV–vis (λmax, nm) 342. MS (EI) *m*/*z*: 635.8 (M+-BF4, 9%) for C21H20I2NO2S2] +.
