Patent GB-807907-A (GB)
Title: Aldehyde diacylates and process for producing the same
Filed: 1957-03-21
Abstract: Mixtures of boric acid and oxalic acid containing not less than 0.01 mol. per cent of either acid are used as catalysts in the preparation of aldehyde diacylates from saturated or unsaturated aliphatic aldehydes and saturated or unsaturated aliphatic carboxylic acid anhydrides (see Group IV (b)).  The catalyst mixture may be prepared in its preferred form by dissolving equimolar amounts of the acids in water to form a 30 per cent solution at 60 DEG  C. and then evaporating to dryness under reduced pressure.  In use the catalyst may first be dissolved in either reagent or in an inert solvent such as isopropyl ether, heptane, benzene, cyclohexane or dioxane.ALSO:Resins are prepared by copolymerizing 1:1-diacetoxy-2-butene, 1:1-diacetoxy-2-propene, 1:1 - diacetoxy - 2 - methyl - 2 - propene, 1:1-diacetoxy - 2:4 - hexadiene, 1:1 - diacetoxy-2 - ethyl - 2 - hexene, 1:1 - dicrotonoxy - 2-butene or 1:1-dicrotonoxybutane with a monomer such as vinyl chloride.  The preparation of the diacylates is described (see Group IV (b)).ALSO:The invention comprises 1 : 1-diacetoxy-2 : 4-hexadiene, 1 : 1 - diacetoxy - 2 - ethyl - 2-hexene, 1 : 1 - dicrotonoxy - 2 - butene and 1 : 1-dicrotonoxybutane and a method for the preparation of these and other aliphatic saturated or unsaturated aldehyde diacylates which comprises reacting an aliphatic aldehyde with an aliphatic carboxylic acid anhydride at a temperature between - 20 DEG and 100 DEG  C. in the presence of a mixture of boric and oxalic acids as catalyst, the catalyst mixture containing not less than 0.01 mol. per cent of either acid.  The preferred catalyst is obtained by dissolving equimolar amounts of the two acids in water to form a 30 per cent solution at 60 DEG  C. and then evaporating to dryness under reduced pressure.  In use, the catalyst may first be dissolved in either reagent or in an inert diluent; a concentration of about 0.02-0.5 weight per cent is preferably used.  The mol. ratio of carboxylic acid anhydride to aldehyde may vary from 0.2 : 1 to 10 : 1 preferably from 1 : 1 to 1.25 : 1.  The reaction may be effected batchwise or continuously, using saturated or unsaturated aldehydes including octatrienal and propargyl aldehyde and saturated or unsaturated anhydrides including mixed anhydrides of saturated and/or unsaturated acids.  In examples: (1) the boric acid-oxalic acid catalyst described above is dissolved in a portion of acetic anhydride and mixed with benzene; some 2 : 4-hexadienal is added and then a mixture of additional aldehyde and anhydride is run in at 25-30 DEG  C.; thereafter, the catalyst is neutralized and the mixture distilled to recover 1 : 1-diacetoxy-2 : 4-hexadiene; (2) the catalyst of (1) is dissolved in crotonic anhydride and then butyraldehyde is slowly added at 25-50 DEG  C. and the reacted mixture is worked up as before to recover 1 : 1-dicrotonoxybutane; (3) the catalyst of (1) is dissolved in crotonaldehyde and then crotonic anhydride is added slowly at 30-40 DEG  C. and the reacted mixture is worked up to recover 1 : 1-dicrotonoxy-2-butene which is identified by complete bromination of the double bonds; (4) acetic anhydride is reacted with 2-ethyl-3-propyl acrolein by the method of (2) to yield 1 : 1-diacetoxy-2-ethyl-2-hexene and some 1 - acetoxy - 2 - ethyl - 1 : 3 - hexadiene formed as a by-product by cleavage from the diacetoxy compound; (5) acetic anhydride and crotonaldehyde are reacted by the method (1) yielding 1 : 1-diacetoxy-2-butene; (6) 1 : 1-diacetoxy propene is obtained by the method of (2) from acetic anhydride and acrolein, some of the 1 : 1-compound being isomerized to the 1 : 3-derivative; and (7) 1 : 1-diacetoxy-2-methyl-2-propene is similarly prepared from acetic anhydride and methacrolein.  The named 1 : 1-diacylates may be copolymerized with monomers such as vinyl chloride to produce resins.