Process for preparing 3-(4)-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-8

A process for preparing 3- or 4-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-8 which comprises contacting dicyclopentadiene with carbon monoxide and hydrogen in the presence of a rhodium catalyst at 110.degree. to 150.degree. C. and 50 to 400 atmospheres, said catalyst being present in an amount of 1 to 30 ppm of rhodium, based upon the amount of dicyclopentadiene employed, said rhodium being present in the form of an organic phosphine-carbon monoxide containing complex.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a process for preparing 3- and 
4-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-8 by hydroformylating 
dicyclopentadiene. By virtue of the presence of two double bonds, 
dicyclopentadiene can form both monoaldehydes and dialdehydes when reacted 
with carbon monoxide and hydrogen in the presence of carbonyl-forming 
metals of Group VIII of the Periodic System. 
2. Discussion of the Prior Art 
The preparation of the dialdehyde, namely, the chemical compound 
tricyclodecane-dialdehyde from dicyclopentadiene, is described in German 
Pat. No. 928,645. Cobalt compounds yielding cobalt carbonyl hydrogen are 
used as catalysts in this case, optionally in the presence of metallic 
cobalt or iron. The conversion is carried out at 140.degree. C. and at a 
synthesis gas pressure of 180 atmospheres. 
UK Pat. No. 801,734 describes the use of rhodium-containing catalysts, 
which are present dissolved in the reaction mixture under the process 
conditions, for the hydroformylation of dicyclopentadiene. An unsaturated 
tricyclodecene-monoaldehyde having a structure not described in more 
detail is obtained in a yield of 68 percent as reaction product under the 
reaction conditions employed, namely, a temperature of 100.degree. C. and 
a pressure of approximately 197 atmospheres. 
Of the two double bonds in the cyclopentadiene molecule, the double bond in 
the norbornene ring is generally the more reactive. It is therefore to be 
expected that hydroformylation will preferentially result in the formation 
of 8- and 9-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-3. 
It therefore became desirable to provide a process which yields the 
isomeric compounds 3- and 4-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-8 in 
good yields by hydroformylation of the cyclopentene ring. 
SUMMARY OF THE INVENTION 
Surprisingly, it was found that the hydroformylation of dicyclopentadiene 
at temperatures of 110.degree. to 150.degree. C. and pressures of 50 to 
400 atmospheres produces 3- and 4-formyltricyclo-[5,2,1,0.sup.2,6 
]-decene-8 in a high yield if the conversion is carried out in the 
presence of 1 to 30 ppm of rhodium, based on the amount of 
dicyclopentadiene employed, said rhodium being present in the form of an 
organic phosphine-carbon monoxide containing complex. 
By maintaining a very low concentration of rhodium, namely, 1 to 30 ppm of 
rhodium based upon the amount of dicyclopentadiene, the hydroformylation 
of dicyclopentadiene produces 3- and 4-formyltricyclo-[5,2,1,0.sup.2,6 
]-decene-8 in high yields. The rhodium complex compound is preferably used 
in an concentration of 10 to 20 ppm of metallic rhodium. The rhodium can 
be added to the reaction mixture in the form of rhodium sesquioxide. It 
is, however, also possible to add rhodium in another form, e.g., as 
rhodium trichloride, as the nitrate, sulfate, 2-ethylhexanoate (salt of 
2-ethylhexanoic acid), or also as the metal. Under the reaction conditions 
and in the presence of organic phosphines, a soluble, catalytically active 
rhodium complex compound is formed, which also contains carbon monoxide in 
addition to phosphine. Obviously, this compound can also be prepared 
separately before the actual hydroformylation and then subsequently added 
to the reaction mixture. Finally, one can add the rhodium in combination 
with a carrier, in which case it is expedient for the rhodium compound to 
be present in an amount of approximately 1 to 40 percent by weight 
referred to the carrier. 
The use of organic phosphines, e.g., triaryl, especially triphenyl, and in 
particular trialkyl, especially C.sub.1-8 alkyl, phosphines, in 
conjunction with the rhodium complex compounds as catalyst is particularly 
important. These phosphines can exist not only in the form of complexes 
but also as free compounds in the reaction mixture. Their concentration 
should be 50 to 1,000 ppm, based on the rhodium. Concentrations of 100 to 
600 have proven particularly suitable. Suitable triaryl phosphines are in 
particular triphenyl phosphine and tritolyl phosphine, and suitable 
trialkyl phosphines are in particular trioctyl phosphine. It is not 
necessary to use pure triaryl or trialkyl phosphines. Instead, mixtures of 
various triaryl or trialkyl phosphines can also be used. 
Temperatures of 110.degree. to 150.degree. C., and in particular 
120.degree. to 140.degree. C., have proven particularly suitable as the 
reaction temperature. Higher temperatures reduce the reaction time, but 
increase the formation of by-products such as aldols. The conversion is 
carried out at pressures of 50 to 400 atmospheres, advantageously in the 
range of from 200 to 300 atmospheres. 
According to a preferred embodiment of the process in accordance with the 
invention, the conversion is carried out in the presence of an inert 
solvent. Suitable solvents are, for example, aliphatic and aromatic 
hydrocarbons such as heptane, hexane, cyclopentane and toluene. One to 
three parts by volume of solvent are preferably used per one part by 
volume of dicyclopentadiene. 
Particularly contemplated types of phosphines include aliphatic straight or 
branched chained phosphines, cycloaliphatic phosphines, aromatic 
phosphines, arylaliphatic phosphines, phosphines with one or more 
substituted cyclic substituents and organic phosphines with two or more 
phosphorous atoms with from 1 to 30 carbon atoms. Examples of specific 
phosphines useful in the process of this invention are: 
tri-n-butylphosphine, tri-n-octylphosphine, tri-i-propylphosphine, 
dicyclohexylphosphine, tricyclohexylphosphine, diphenylphosphine, 
triphenylphosphine and 1,3-bis-(diphenylphosphino)-propane. 
After the end of the hydroformylation, the reaction mixture is worked up by 
cooling and lowering the pressure of the reactor contents. After 
decomposing the rhodium carbonyl compounds, e.g., by introducing nitrogen, 
the isomeric monoaldehydes are distilled off. Small amounts of catalyst 
remaining in the crude product are thereby decomposed. 
The process according to the invention can be carried out batchwise, as 
well as semi-continuously or fully continuously. 
The aldehydes obtained according to the new method are used as components 
in perfume and fragrance compositions, as well as intermediates in the 
manufacture of synthetic rubber.

In order to more fully illustrate the nature of the invention and the 
manner of practicing the same, the following example is presented: 
EXAMPLE 
Preparation of 3-(4)-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-8 
200 g of dicyclopentadiene, 200 ml of toluene, 5 mg of rhodium (=25 ppm) in 
the form of rhodium-2-ethylhexanoate and 1,27 g of triphenylphosphine are 
placed in a 1 liter volume autoclave. After flushing with nitrogen, a 
mixture of carbon monoxide and hydrogen (volume ratio 1:1) is added to the 
reactor to a pressure of 100 atmospheres. The reactor contents are then 
heated to 130.degree. C. and the pressure is raised to 270 atmospheres by 
pumping in CO/H.sub.2 and is maintained constant during the reaction by 
the continuous addition of the gas mixture. After two hours, the reaction 
is discontinued and the reaction mixture is analyzed by gas 
chromatography. At a 98 percent conversion, the crude product contains 88 
percent of 3-(4)-formyltricyclo-[5,2,1,0.sup.2,6 ]-decene-8.