DE1768306B1 - Process for the preparation of esters of 2-hydroxymethyl-norbornene- (5) - Google Patents

Description

The invention relates to a process for the preparation of esters of 2-hydroxymethyl-norbornene- (5) the general formula

R —CO-O —CH,

in which R denotes an alkyl radical having 1 to 4 carbon atoms, which is characterized in that a mixture of 2-aldehydo-norbornene- (5) and a lower aliphatic aldehyde of the formula R — CH O Subjected to a Tishchenko reaction in the presence of an aluminum alcoholate as a catalyst.

So far, such esters have been made by diene synthesis from cyclopentadiene and the corresponding allyl ester manufactured; their direct production from a lower aliphatic aldehyde and 2-aldehydo-norbornene- (5), this in turn is very easily accessible by diene synthesis from cyclopentadiene and acrolein is, was not known.

It has surprisingly been found that the implementation of a mixture of 2-aldehyde-norbornene- (5) and a lower aliphatic aldehyde in the presence of a catalytic amount of an aluminum alcoholate leads in a very selective manner to the desired asymmetric ester (I), while in fact four esters would be possible as reaction products, namely the two symmetrical esters, the by Tishchenko reaction of each of the aldehydes with itself result:

R-COO-CH ₂ -R and No2-COO-CH ₂ -No2

as well as the two asymmetric esters, which are formed by the mutual reaction of the two aldehydes:

No2-COO-CH ₂ -R and R-COO-CH ₂ -No2

where No 2 is the 2-norbornylene radical.

It has been shown that the selectivity is very much reduced when you are in the homologous Series of aliphatic aldehydes moves upwards and that therefore the practical value on the use limited to the low links defined according to the invention. The for the invention Process usable aldehydes are R — CHO Acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde and pivalaldehyde.

Both aldehydes are preferably reacted in a quantitative ratio which is the stoichiometric Quantity ratio comes close. However, it is also possible to use a slight excess of one of the aldehydes to be used, and in this case an excess of the aldehyde R — CHO of about 30 to 50% apply. The reaction is in the presence of an aluminum alcoholate, in particular of Aluminum ethylate or isopropylate, carried out, the catalyst in an amount of 0.1 to 5 g / mole of aldehyde is present.

The reaction can be carried out either without a solvent or in the presence of an inert solvent for example, in the presence of a saturated hydrocarbon such as η-hexane and cyclohexane or an aromatic hydrocarbon such as benzene or toluene. One can use as a solvent as well use a carboxylic acid ester produced by the reaction. It's also cheap to have one Ester of structure

R-COO-CH ₂ -R

to use which corresponds to the aliphatic aldehyde used, for example ethyl acetate Use of acetaldehyde. The reaction can also be carried out in the presence of a mixture of these various possible solvents.

It is preferred to work at a temperature between 0 and 70 ° C. and with gradual mixing the reactant to avoid runaway the reaction, which is exothermic. For example, a solution of the catalyst is added to the mixture of aldehydes or vice versa, adjusting the temperature by cooling the reaction vessel.

The esters prepared according to the invention can be used as monomers according to US Pat. No. 3,245,928 be used. Saponification gives the corresponding alcohol, 2-methyl-norbornene- (5), the itself is valuable as a monomer and is suitable for homopolymerization or copolymerization with ethylene suitable (U.S. Patent 3,277,036), as well as with numerous vinyl monomers, such as vinyl chloride or Vinyl acetate (U.S. Patent 3076793) or acrylic compounds (U.S. Patent 2,985,611) is copolymerizable.

example 1

2-Methylol Norbornene (5) Acetate

^{A solution of 4 g of aluminum isopropoxide in 100 cm 3 of} cyclohexane was placed in a round-bottom flask equipped with a stirrer and reflux condenser, and a solution of 122 g of 2-aldehyde-norbornene (5) (1 mol) and 55 g of acetaldehyde (1.25 mol ) added in 160 cm ^{3 of} cyclohexane. During the addition, the temperature was kept at 17-20 ° C by cooling with ice. It was on for 1 hour

4O ⁰ C heated, then cooled and 10 cm ³ of a lnormalen aqueous solution of sulfuric acid was added to neutralize the catalyst. The aqueous phase was decanted off, then was first distilled at atmospheric pressure in order to isolate the cyclohexane and the ethyl acetate (14 g) formed from part of the acetaldehyde, then the distillation was carried out at a pressure of 10 mm Hg, with a temperature of 80 to 83.5 ° C 141 g of a fraction were obtained, the 97 percent by weight of the acetate of 2-methylolnorbornene (5) and 2.3 percent by weight of 2-methylolnorbornene (5) and a trace of the unconverted 2-aldehyde-norbornene - (5) as analyzed by gas chromatography.

Based on the 2-aldehydo-norbornene- (5) used, the acetate of 2-methylol-norbornene- (5) was accordingly obtained in a yield of 82.5% of theory.
The distillation residue was 13 g and consisted mainly of the norbornene- (5) -2-carboxylic acid ester of 2-methylol-norbornene- (5), which was formed by the reaction of 2-aldehyde-donorbornene- (5) with itself (about 10% ).

Example 2
2-Methylol Norbornene (5) Acetate

A solution of 10 g of aluminum isopropoxide in 250 g of a mixture of 55 percent by weight ethyl acetate and 45 percent by weight cyclohexane was prepared. While maintaining a temperature of 2O ⁰ C was followed by a Gemicsh of 610 g 2-aldehydo-norbornene (5) (5 moles), 275 g of acetaldehyde (6.25 moles) and 500 g of a mixture of 55% ethyl acetate and 45 weight percent Cyclohexane introduced. After the addition, which took place during a time of 2 hours, 4 hours was heated to 40 ⁰ C, then cooled and 50 cm ³ trains give a lnormalen aqueous solution of sulfuric acid. The aqueous phase was decanted off and the solvents were removed by distillation at atmospheric pressure. Fractional distillation under a pressure of 10 mm Hg gave 676 g of a fraction boiling at 80 to 83.5 ° C with the following data: nf = 1.472, df = 1.031, analysis of which by gas chromatography showed that it contained 660 g (3, 97 mol) of the acetate of 2-methylol-norbornene- (5), that is 79.5% of theory, 6.8 g of 2-methylol-norbornene- (5), and 6.6 g of the ethyl ester of norbornene- ( 5) -2-carboxylic acid. The data given in the literature for the acetate of 2-methylol-norbornene- (5) are: Bp. ₇ = 83.5 to 84 ⁰ C, nl ° = 1.4754, df = 1.035 (Chem. Abstr. 52, 12775).

A residue remained which was composed of 69 g of the 2-methylol-norbornene (5) ester the norbornene (5) -2-carboxylic acid (11.3%, based on the amount used) Aldehyde).

Example 3
2-Methylol Norbornene (5) n-Butyrate

35

A solution of 2 g of aluminum isopropylate in 100 cm ^{3 of} cyclohexane was prepared and a mixture of 61 g (0.5 mol) of 2-aldehyde-norbornene-5 and 36 g (0.5 mol) of n- Butyraldehyde was introduced while adjusting the temperature to 6O ⁰ C. The addition took 1 hour and was then allowed to react for 2 hours at the same temperature. The mixture was then cooled to room temperature, 10 cm ^{3 of} a normal aqueous solution of sulfuric acid were added and the aqueous phase was separated off by decanting. Then the cyclohexane was distilled off at atmospheric pressure and the reaction product was analyzed by gas chromatography. It contained 56 g of the n-butyrate of 2-methylol-norbornene- (5) (0.29 mol), 21 g of n-butyl-n-butyrate (0.15 mol), 19 g of the norbornene- (5) - 2-carboxylic acid ester of 2-methylol-norbornene- (5) (0.08 mol), 1.1 g of the norbornene- (5) -2-carboxylic acid ester of n-butanol and 3.7 g of 2-methylol-norbornene- ( 5). The fractional distillation of the mixture was then carried out under a pressure of 10 mm Hg, 59 g of a fraction with the data bp. _Lo = 115.5 to 116 ° C., nl ° = 1.469, d% ° = 1.003 being obtained 95 to 96 percent by weight of the n-butyrate of 2-methylol-norbornene- (5) contained (57.5% of theory). The physical data given in the literature for this product are: bp _u = 114 to 115 ° C, nf = 1.4765, di ° = 1.016 (Chem. Abstr. 52, 12 775).

Claims (2)

Patent claims: 1. Process for the preparation of esters of 2-hydroxymethyl-norbornene- (5) of the general formula R - CO - O - CH, in which R denotes an alkyl radical with 1 to 4 carbon atoms, characterized in that that one is a mixture of 2-aldehyde-norbornene- (5) and a lower aliphatic aldehyde of the formula R — CHO in the presence of an aluminum alcoholate as a catalyst for a Tishchenko reaction subject. 2. The method according to claim 1, characterized in that one carries out the reaction at 0 to 70 ⁰ C.