preparation method of 2,4,6-trimethylpyranium tetrafluoroborate_industrial additives

background and overview of the preparation method of 2,4,6-trimethylpyranium tetrafluoroborate

2,4,6-trimethylpyranium tetrafluoroborate can be used as a pharmaceutical synthesis intermediate.

preparation method of 2,4,6-trimethylpyranium tetrafluoroborate

method 1: add acetic anhydride (100ml, 1.06mol, 13.0 equivalent) and tert-butanol (8.00ml, 84.2mmol, 1.00 eq.) to a round-bottomed flask equipped with a condenser and dropping funnel. fluoboric acid (14 ml, 78 mmol, 0.95 equiv) was added dropwise. during its addition, the temperature increased to 80°c. after the exothermic reaction was completed, the mixture was cooled to 5°c and cold et2o was added, the precipitate was collected, washed with cold et2o and dried. 2,4,6-trimethylpyranium tetrafluoroborate was obtained as a colorless solid (11.6 g, 55.4 mmol, 71%). 1h nmr (300mhz, cd3od, 300k) δ = 7.87 (s, 2h, charopicoline m), 2.88 (s, 6h, 2×ch3), 2.72 (s, 3h, ch3). 13 c nmr (75mhz, cdcl 3, 300k) δ = 179.5 (cq), 134.1 (cq), 124.3 (ch), 21.1 (ch 3), 20.7 (ch 3). 19f nmr (282mhz, cd3od, 300k) δ = -154.7. hrms (esi) m/z = 123.0804 calculated value. ms (esi): c8h11o [m] +, found: 123.0762. the spectral data are consistent with previously reported data.

method 2: place acetic anhydride (1kg, 9.79mol, 10 equivalents) in a 2l double-neck round-bottomed flask. at room temperature, 4-hydroxy-4-methyl-2-pentanone (122 ml, 0.98 mol, 1 equiv) was added over 5 minutes using a pressure-equalizing dropping funnel, and the solution was stirred for 5 minutes. use a pressure-balanced dropping funnel to add hbf4 (127 ml, 48% aqueous solution, 0.97 mol, 1 equiv) dropwise in 1 hour of zinc borate. the temperature of the reaction mixture during the addition was approximately 90°c. the color of the solution gradually changes from colorless to light orange to dark brown. the reaction mixture was heated and stirred at 80°c for an additional hour and then cooled to room temperature. the light-colored precipitate was filtered off with suction and washed with a total of 1 l of diethyl ether to obtain 135 g (0.64 mol, 66%) of light yellow crystalline 2,4,6-trimethylpyridine tetrafluoroborate. yield 135g (0.64mol, 66%) melting point (uncalibrated): 219.6-220.3℃dec. 1h nmr (cd3cn, 300 mhz, 20°c): δ 7.72 (s, 2h, m-methyl), 2.80 (s, 6h, o-methyl), 2.65 (s, 3h, p-methyl) ppm.