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Example 1: Preparation of 3, 9-diethylidene-2,4, 8,10-tetraoxaspiro [5.5] undecane, DETOSU, 1. To a clean, dry 22 L photochemical reactor fitted with a thermowell, condenser, and mechanical stirrer, under nitrogen atmosphere was added 10 L pentane and 2072g (9.76 mol) <strong>[78-19-3]3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane</strong>, 2. The mixture was stirred at reflux for 40 minutes to degas the solvent, then 5.9 mL (8.79 g, 44.9 mmol, 0.45 mol%) iron pentacarbonyl was added, and the solution refluxed for an additional 15 minutes. The resulting solution was refluxed under irradiation with a 450 W medium pressure quartz mercury vapor UV lamp (Ace-Hanovia) in a reflector housing for 30 minutes, refluxed without irradiation for 90 minutes, refluxed under irradiation for 40 minutes, and refluxed without irradiation for 6 hours, by when GC showed that the starting material had been consumed and the amount of partially isomerized material was less than 5%. The reaction mixture was allowed to cool overnight while stirring, still under nitrogen atmosphere. About 10% (1 L) of the cooled reaction mixture was removed and used for in-process analysis. To the reactor containing the remaining 90% of the reaction mixture was added 50 mL triethylamine, and most of the pentane was removed by distillation under nitrogen atmosphere at atmospheric pressure with a pot temperature of 30-40C. The crude DETOSU, 1, wet with solvent, about 3.5 L, was dried (pressure 1-3 mbar, pot temperature 45-50 C) to give 1.9 Kg dried crude DETOSU (100% crude yield, 5% partially isomerized material by GC); and this was distilled in a short-path distillation apparatus with boiling chips (pressure-3 mbar, pot temperature 124-165C, head temperature 121-129C) to give 1762 g distilled crude DETOSU. To a clean, dry 22 L flask fitted with a thermowell, condenser, and mechanical stirrer, under a nitrogen atmosphere was added the distilled crude DETOSU from the previous paragraph, 10.6 L heptane, and 10 mL triethylamine. The mixture was heated to dissolution (~80C) with stirring, and allowed to cool to room temperature overnight, still under nitrogen atmosphere. Some gummy brown material was noticed adhering to the walls of the flask and thermowell; so the solution was decanted and the apparatus cleaned before returning the solution to the flask. The solution was reheated to 80C, resulting in a slightly cloudy solution, then cooled to -10C and crystallization started by scratching the inside of the flask walls with a glass rod. The solution warmed about 4C during crystallization before returning to -10C over about one hour. The mixture was held at -10C for an additional hour, then cooled to-20C and held for 15 minutes. The crystalline DETOSU was collected by cold centrifugation, using a Western States Model 1000-1476 perforated basket laboratory centrifuge fitted with a 60 um filter bag, under nitrogen atmosphere. The centrifuge was precooled with 4 L of -30C pentane while rotating, then the crystalline DETOSU slurry added under 100-160 xg, ensuring that excessive liquid did not accumulate in the basket. The centrifuge speed was increased to -1000 XG to dry the filter cake, which was then washed with 2.5 L of -30C pentane and centrifugation continued for an additional 30 minutes. A first crop of 927 g (54% yield, 2.8% partially isomerized material by GC) crystalline DETOSU was obtained. A second crop of 527 g was obtained from the mother liquor by a similar process, giving a total of 1513 g (82% yield) of crystalline DETOSU. The crystalline DETOSU was recrystallized using 8.5 L pentane and 8.5 mL triethylamine to give 982 g recrystallized DETOSU in the first crop; and this was distilled (pressure-3 mbar, pot temperature 129-145C, head temperature 121-129C) to give 879 g purified DETOSU, 1 (51% overall yield NMR consistent with structure of clean desired product, 1.7% partially isomerized material by GC). |
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With iron pentacarbonyl; for 8.25h;Inert atmosphere; Irradiation; |
DETOSU:In a 200 mL photochemical reactor with a thermowell and a condenser,It is also filled with nitrogen gas.100 mL of n-pentane and 20.72 g (97.6 mmol)3,9-divinyl-2,4,8,10-tetraoxanodecane is added to the reactor,The gas in the solvent was removed by stirring at reflux temperature for 40 min.Then 0.059 mL (87.9 mg) of iron pentacarbonyl was added to the mixture.Stirring was continued for 15 min at reflux temperature.The reaction solution is at reflux temperature,Irradiation with a 450W medium pressure quartz pump vapor arc lamp reflector for 30 minutes,Then remove the mask,The reaction was continued at reflux temperature for 90 min.Then the light reacted for 40 minutes.Remove the mask,Continue to react for 6h,When the raw material is shown to be consumed and the isomer material is less than 5%,The reaction solution was cooled and stirred overnight.Finally add 0.5mL of triethylamine,Remove n-pentane by distillation, obtained by vacuum drying to get rough3,9-diethylene-2,4,8,10-tetraoxa-[5.5]undecane(DETOSU) crude product,The pure DETOSU is then obtained by dissolving and distilling three times through n-heptane. |
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