IL32433A - Octahydro-1,2,4-methenopentalene-5-carboxylic acid alkoxyalkyl esters and process for their production - Google Patents

Description

32435/3 New octahydro-1, 2,4-methenopentalanes-*5- carboxylic acid alkoxyalkyl esters and process for their production J. R. G E I G Y A. G. BAS EL 21 - 2848 * New octahydro-1, 2 , 4-methenopentalene-5-carboxylic acid alkoxy- alkyl esters and process for their production The present invention concerns new alkoxyalkyl ' esters' of octahydro-1 , 2 , 4-methenopentalene-5-carboxylic acid, as well as a continuous process for the production thereof.

The designation "Octahydro-1 , 2 , 4-methenopentalene" is taken from "The Ring Index" [A.M. Patterson, Suppl. I, Am. Chem. Soc. 1963] and denotes the ring, system This reference also gives the following designations for the same compound: Tetra.cyclo[_ .3.0.0.2> and quadricycloL 2.2.1.0 2 * 6.2 , 3 ' 5] nonane .

Quite a number of octahydro-1 ,2, -methenopentalene-5-carboxylic acid derivatives, such as esters, nitriles, amides, substituted amides, etc. are known. " Thus, for example, in the U.S. patent No. 3,271,433 a discontinual process is described according to which 2 , 5-norbornadi ene is heated in the presence of a nickel(O) catalyst with acrylic acid-alkyl esters at temperatures between 80 and 300°C under a pressure of from 1 to 100 atmospheres. The' German specification open process for the production of the ethyl ester by reacting 2 , 5-norbornadiene with acrylic acid ethyl ester in the presence of nickel tri carbonyl-triphenyl phosphine at temperatures of 80 to 90°C. The compounds obtained according to these processes are not only important intermediate products in the production of pesticides and pharmaceuticals, but they themselves possess biocidal activity.

The octahydro-1 , 2 , 4-methenopentalen e-5-derivatives obtained according to the processes described above are isomeric mixtures. The separation of such mixtures - if at all possible - is technically very uneconomical. For the production of pharmaceuticals j however, isomerically pure intermediate products are desired. Moreover, the esters of octahydro-1 , 2 , - methenopentalene-5-carboxylic acid which have been hitherto known have such an unpleasant intrinsic smell, that they could not be used as biocidal substances or intermediate products [G.N. Schrauzer et al , Ber. 95, pg. 2768 (1962)].

It was therefore important to develop an economical process which yields practically only a single isomer of octahydro-1 , 2 , -methenopentalene-5-carboxylic acid esters.

The very strong unpleasant smell of the known esters made it urgent to seek a process for the production of new, practically odorless esters, suitable for further reactions.

Lower alkoxyalkyl esters of octahydro-1 , 2 , 4-rnetheno-■ pentalene-5-carboxylic acid have not been hitherto known.

These esters are reactive, practically odorless and are therefore especially suited as intermediate products for the production of pharmaceuticals and biocidal substances.

The new octahydro-1 ,2,4 -methenoper:talene-5-carboxylic acid alkoxyalkyl esters of the formula wherein R represents an alkoxyalkyl radical with 2 or 3 carbon atoms in the alkylene moiety and from 1 to 4 carbon atoms in the alkoxy moiety, are produced according to the invention by continously reacting a mixture of 2 , 5-norbornadiene , an acrylic acid alkoxyalkyl ester of the formula CE = CH - COOR . . II wherein R has the meaning given above, and a nickel(O) catalyst at temperatures between 150 and 200° C, preferably under normal pressure and with a continual supply of the starting materials adapted to the rate of the reaction. According to this continual process, to be sure, a mixture of the endo and exo isomers of \ the corresponding esters are obtained, but the mixture contains % or more of the. exo isomer.

The amount of the individual isomers was determined by the nuclear resonance spectra. The yields range between 85 and 95%. As impurities, polymerization products are obtained which can easily be removed by distillation.

Acrylic acid alkoxyalkyl esters of the formula II which are particularly suitable for the process are the following: acrylic acid- -ethoxy-ethyl ester, acrylic acid-P-rnethoxyethyl ester, acrylic acid^-n-propoxy- , isopropoxyethyl ester, acrylic acid- -n-butoxy-ethyl ester, also the γ-methoxy-, γ-ethoxy-, γ-propoxy- and γ -butoxypropyl esters of acrylic acid. In order advantageous..to use the appropriate acrylic acid ester together with a stabilizer. The stabilizer must be inert towards the nickel catalyst. Suitable ones are, e.g., hydroquinone-alkyl ethers, dialkyl and trialkyl phenols. The acrylic acid ester should contain from 0.001 to 0.4% of stabilizer.

Suitable nickel(O) catalysts are nickel carbonyls, nickel phosphines and, in particular, partially carbonyl-substituted nickel phosphine derivatives such as nickel tricarbonyl-tri- phenyl phosphine, nickel dicarbonyl-di- ( triphenyl phosphine), as well as other nickel(O) compounds corresponding to the formula iLPCOR)^]^ in which R represents an aliphatic or aromatic hydrocarbon radical. For the process according to the invention, nickel tricarbonyl-triphenyl phosphine is especially suitable as catalyst.

Norbornaaiene and acrylic acid ester are used in the reaction in a molar ratio in the range of from 1:1.15 to 1:4. The amount of catalyst added is preferably from.1 to 15 per cent by weight, calculated on the diene. It is advisable to work under an atmosphere of nitrogen, since the nickel catalysts mentioned are very sensitive to oxygen. .

In the continual process according to the invention, the . reaction components are first combined. A small part of this mixture is then, heated until the reaction commences. For the . production of the β-ethoxyethyl ester of octahydro-1 , 2 , 4-methenopentalene-5-carboxylic acid,. it must be heated to 170-180°C. As soon as the reaction subsides, the bulk of the reaction product is added. Simultaneously, the reaction product is removed from the reaction vessel. The addition of the reaction mixture and the removal of the reaction product must be so regulated ' tha t the temperature in the reaction vessel remains constant, in the case of the β-ethoxy-ethyl ester at 170-180° The reaction takes place immediately. When the temperature sinks a fev; degrees, the reaction may stop without the possibility of being started again. It is also necessary to as sure that the mixture of the reaction components has been freshly prepared; mixtures which are several hours old cannot be completely reacted under the described conditions.

The following example illustrates the process according to the invention. The temperatures are given in degre Centigrade. Unless stated otherwise percentages are by weight J Example 3312 g of acrylic acid^-ethoxy-ethyl ester, stabilized with 0.2% of hydroquinone-monomethyl ether, 1852 g of 2,5-norbornadiene and 148 g of nickel- tricarbonyl-triphenyl phos-phine are combined. 500 ml of this mixture are heated to 170° in a flask equipped with a discharge until the strongly exothermic reaction commences. As soon as the reaction subsides (lowering of the inner temperature from 180 to 170°C) the ester/diene/catalyst mixture is added in such a manner that the inner temperature is 17CP-1800. Simultaneously the reaction product, namely the octahydro-1 , 2 , -methenopentalene-5-carboxylic acid-p-ethoxy-ethyl ester, is removed through the discharge. Addition and removal are so regulated that there are constantly 1500 ml of the reaction mixture in the reation vessel. After 2.5 to 3 hours the reaction of the batch is completed. For purification, the ester is fractionated in vacuo; its boiling point is 115° at 0.5 Torr (uncorrected), and 100° at 0.005 Torr. The refractive index njuis: 1.4833$ the yield is 88 of the theoretical.

The ester obtained is an isomeric mixture. Using the nuclear resonance spectra and gas chromatograms , it was determined that the ratio of the exo isomer to the endo isomer v/as practically 9:1.

The following compounds are obtained in the same manner as described in the foregoing example: Octahydro-1, 2 , 4 -meth nopentalene-5-carboxylic acid- -methoxy-ethyl' ester, B.P. 100-102° / 0.15 Torr; Octahydro-1 ,2, -methenopentalene-5-ca'rboxylic acid-P-propoxy-ethyl ester; Octahydro-1 , 2 , 4-methenopen.talene-5-carboxylic acid-p-isopro-poxy-ethyl ester, B.P. 113-115° / 0.8 Torr; Octahydro-1 , 2 , 4-methenopentalene-5-carboxylic acid-p-n-butoxy-ethyl ester, B.P. 113-115° / 0.001 Torr; Octahydro-l , 2 , 4-methenopentalene-5-carboxylic acid-y-methoxy-propyl ester; Octahydro-1, 2, -methenopentalene-5-carboxylic acid-γ -ethoxy-propyl ester, Octahydro-1, 2, 4-methenopentalene-5-carboxylic acid-γ -n-propoxy-propyl ester; Octahydro-1, 2, -methenopentalene-5-carboxylic acid-γ -n-butoxy-propyl ester.

Claims (5)

What- we claim is:

1. Octahydro-1, 2, 4-methenopentalene--5-carboxylic acid-alkoxyalkyl ester of formula I wherein R represents an alkoxyalkyl radical with 2 or 3 carbon .atoms in the alkylene moiety and from 1 to 4 carbon atoms in the alkoxy moiety..

2. Octahydro-1 , 2 , 4 -methenopentalene-5-carboxylic acid-β-ethoxy-ethyl ester.

3. Process for the production of octahydro-1, 2, 4 -metheno-pentalene-5-carboxylic acid alkoxyalkyl esters of formula I wherein R represents an' alkoxyalkyl radical with 2 or 3 carbon atoms in the alkylene moiety and from 1 to 4 carbon atoms in the alkoxy moiety, characterized by continually reacting a mixture of 2,5-norborn-adiene, an acrylic acid alkoxyalkyl ester of the formula II CH2 - CH-COOR II wherein R has the meaning given above, and a nickel(O) catalyst at temperatures between 150 and 200°C and with a continual supply of the starting materials adapted to the rate of the reaction.

4. Process according to Claim 3, characterized b Nusing acrylic acid-B-ethoxyethyl ester as the acrylic acid alkoxy-alkyl ester of formula II and performing the reaction at temperatures between 170 and 180°C.

5. Process according to Claims 3 and 4, characterized by using nickel-tricarbonyl-triphenyl phosphine as nickel(O) catalyst.