DE3227108A1 - Process for the preparation of pivalolactone - Google Patents

Abstract

The invention relates to a process for the preparation of pivalolactone by reacting dimethyl ketene and formaldehyde in the presence of Lewis acid, iodine being added as co-catalyst.

Description

Process for the manufacture of pivalolactone

The invention relates to a method for the production of, also as 3.3-dimethyl-oxetanone-2 to be designated pivalolactone.

It is already known from US Pat. No. 3,221,028, for example dimethylketene and to convert formaldehyde in the presence of Lewis acids to pivalolactone. Unfortunately 2.2.4.4-Tetramethylcyclobutanedione (1.3) is produced as a by-product in this process, which interferes with the polymerization of the pivalolactone to form the corresponding polyester. That The by-product mentioned must therefore be removed, which is because of the similar boiling behavior requires complex fractionation steps.

According to US Pat. No. 3,000,906, it has therefore already been proposed that the aforesaid To hydrogenate dione selectively in the presence of ruthenium, with the corresponding diol which is relatively easy to separate.

As before, however, the fact remains that the procedure although it can be done from a cheap raw material base because of the by-product formation is uneconomical.

The object of the invention was to provide a process for the production of pivalolactone find in which the disadvantages described can be avoided without the cheap raw material base must be abandoned.

It has now been found that the reaction of dimethylketene with formaldehyde with excellent yields and with greatly reduced by-product formation in Presence of Lewis acids proceeds when iodine is used as a co-catalyst is introduced into the reaction mixture.

The invention relates to a process for the production of pivalolactone by reacting dimethylketene and formaldehyde in the presence of Lewis acid, the is characterized in that elemental iodine is added.

The catalyst system according to the invention Lewis acid / iodine is at einmolarem Approach of dimethylketene is preferably used in amounts of 0.001 to 0.01 mol.

The molar ratio of Lewis acid to iodine can be in the range of 1: 100 vary up to 100: 1. It is particularly preferably 1: 1.

Examples of Lewis acids which can be used according to the invention are the halides of boron, --- zinc, aluminum, tin, titanium, iron as well as organic Complexes of the halides mentioned, such as, for example, dietherates. In particular, come Zinc chloride and aluminum chloride are used.

Specific examples of the catalyst system of the present invention are Mixtures of 0.005 moles of aluminum chloride and 0.005 moles of iodine and 0.005 moles of zinc chloride and 0.005 mol of iodine, the amounts mentioned in each case being based on a one-molar approach are obtained from dimethylketene.

The inventive method is preferred in the area of the surrounding Atmosphere, i.e. at 1 bar or about 1 bar and at temperatures of 40 to 70 "C, in particular 50 to 60 "C carried out.

Dimethyl ketene can be in gaseous form, in liquid state or diluted in inert solvents are used.

Suitable solvents for this include non-polar solvents, such as n-hexane and cyclohexane, less polar solvents such as toluene, xylene, tetrachlorethylene and especially polar solvents, e.g. ethers such as dioxane and diethyl ether, Esters, such as ethyl acetate, nitriles, such as acetonitrile, and mixtures thereof.

Formaldehyde can be used both in polymeric form, e.g. as paraformaldehyde or can also be used in monomeric form.

Preference is given to using an excess of formaldehyde. Appropriately 1.1 to 1.5 moles of formaldehyde are used per 1 mole of dimethylketene.

Usually formaldehyde is in solution along with the catalyst system submitted and metered in dimethylketene with stirring.

As a solvent, they already serve as a diluent for diketene mentioned solvents, in particular ether / dioxane mixtures, acetonitrile and ethyl acetate.

If formaldehyde is used in gaseous form, it is advisable to use it at the same time Metering of formaldehyde and dimethylketene in a template of solvent and Catalyst system, the dosage is preferably controlled so that formaldehyde is always present in excess in the reaction mixture.

According to the process according to the invention, it is possible to obtain pivalolactone in high levels Produce yields. Under the reaction conditions according to the invention, the Dimerization of dimethylketene to 2.2.4.4-tetramethylcyclobutanedione occurring as a side reaction suppressed so far that the pure distillation of the target product without difficulty can be carried out.

The invention will now be explained by means of examples and comparative examples explained in more detail: Example 1 100 g (3.3 moles) paraformaldehyde, 0.68 g (0.005 mol) of zinc chloride and 1.27 g (0.005 mol) of iodine were suspended in 2 liters of ethyl acetate and heated to 55 ° C. In the course of 2 hours were added to this mixture under a nitrogen blanket 210 g (3.0 mol) of liquid diketene cooled to -60 ° C. are metered in.

Then the excess paraformaldehyde was filtered off and that Washed the filtrate with water and sodium hydrogen carbonate solution. After distilling off of the solvent in vacuo, the residue was fractionally distilled.

270 g of pivalolactone corresponding to 90% of theory were obtained.

Example 2 100 g (3.3 mol) of paraformaldehyde, 1.36 g (0.01 mol) of zinc chloride, 0.67 g (0.005 mol) of aluminum chloride and 0.76 g (0.0.3 mol) of iodine were dissolved in 2 l of diethylene glycol dimethyl ether suspended and heated to 50 OC. Over 2 hours were with good stirring 190 g of dimethylketene introduced in gaseous form. Thereafter, the reaction mixture was like described in Example 1, worked up.

241 g of pivalolactone, corresponding to 89% of theory, were obtained.

Example 3 A catalyst mixture of 1.36 g (0.01 mol) of zinc chloride and 0.254 g (0.001 mol) of iodine in 2 liters of xylene was heated to 50 "C. Into this mixture simultaneously 100 g (3.3 mol) of gaseous formaldehyde and 190 g (2.71 mol) gaseous dimethyl ketene initiated within 6 hours. The work-up the reaction mixture was carried out as described in Example 1.

The yield was 233 g of pivalolactone, corresponding to 86% of theory.

Comparative Example 1 The procedure according to Example 1 was repeated, with the modification that the work was carried out without the addition of iodine.

It was pivalolactone in a yield of only 70% of theory obtain. The proportion of 2.2.4.4-tetramethylcyclobutanedione (1.3) in the reaction mixture was 26%.

In contrast, the proportion of 2.2.4.4-tetramethylcyclobutanedione (1.3) in the reaction mixture in the procedure according to the invention, as in the examples 1 to 3 was described, only 1%. This proportion was so small that the distillative Work-up of the reaction mixture could be carried out without difficulty.

Claims (3)

Claims process for the production of pivalolactone by Reaction of dimethylketene and formaldehyde in the presence of Lewis acids, d a d u r e k e k e n n n e i n e t that elemental iodine is added. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the amount of Lewis acid and iodine, based on a one-molar approach of dimethylketene, 0.001 to 0.01 mol. 3. The method according to claim 1 and 2, d a d u r c h g e -k e n n z e i c h n e t that the molar ratio of Lewis acid to iodine is 1: 100 to 100 : 1 is.