| 摘要 |
1312193 Production of 6,6-alkylenedioxyheptan-2-ones F HOFFMANN-LA ROCHE & CO AG 7 July 1971 [8 July 1970] 31892/71 Heading C2C 6,6 - Alkylenedioxyheptan - 2 - ones are prepared by (a) reacting diketene with formaldehyde in an aqueous reaction medium to produce 2,6-heptanedione, (b) ketalizing the 2,6-heptanedione with C 2-4 alkylene glycol in the presence of a strong inorganic acid or Lewis acid, (c) removing the 6,6-alkylenedioxyheptan-2-one from the ketalization medium by extraction with sodium bisulphite, and (d) recovering the 6,6- alkylenedioxyheptan-2-one from the sodium bisulphite phase. In stage (a) two moles of diketene are preferably employed per mole of formaldehyde and the reaction is suitably effected at a temperature of 0-100‹ C.; in stage (B) the ketalizing agent employed is preferably ethylene glycol in a molar excess based on 2,6-heptanedione. 2,2,6,6-dialkylenedioxyheptane produced as a by-product in the ketalization step may be selectively hydrolysed with dilute aqueous mineral acid and the hydrolysis product may then be recycled to the sodium bisulphite extraction step. |
