Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-03-07
2001-11-13
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C562S504000, C568S354000
Reexamination Certificate
active
06316659
ABSTRACT:
The present invention relates to a process for preparing cyclopentanone and cyclopentene-1-carboxylic acid and an ester thereof by reacting 5-formylvaleric acid and an ester thereof and/or 6-hydroxycaproic acid and an ester thereof and/or a compound which is converted into 6-hydroxycaproic acid or an ester thereof by reaction of water and alcohols under the reaction conditions, alone or as a mixture with adipic esters, over oxidic catalysts at from 200 to 450° C. in the gas or liquid phase.
EP-A-251 111 discloses the preparation of cyclopentanone by reacting adipic diesters over oxidic catalysts at an elevated temperature in the gas or liquid phase. Furthermore, EP-A-266 687 discloses the use of zeolitic catalysts or phosphate catalysts for this reaction.
It is an object of the present invention to prepare cyclopentanone from starting materials which are even more easily obtainable than adipic diesters (readily obtainable by esterification of adipic acid), even at the cost of the coproduction of a further product of value.
This product of value is cyclopentene-1-carboxylic acid or its esters, which have previously been prepared in a rather complicated way by reduction of cyclopentanone-2-carboxylic esters to give cyclopentanol-2-carboxylic esters and subsequent elimination of water (Heterocycles 47 (1996), 423-425.
We have found that this object is achieved according to the invention by a process for preparing cyclopentanone and cyclopentene-1-carboxylic acid or an ester thereof of the formula I
where R is hydrogen or an aliphatic radical having 1-6 carbon atoms or a cycloaliphatic, araliphatic or aromatic radical having 6-12 carbon atoms, which comprises heating a compound of the formula II
X—(CH
2
)
4
—COOR II
where X is formyl or hydroxymethyl and R is defined as above, and/or a compound which is converted into a compound of the formula II by reaction with water or alcohols ROH under the reaction conditions to from 200 to 450° C. in the gas or liquid phase in the presence of a heterogeneous oxidic catalyst.
In a particular embodiment of the process, a mixture of a compound of the formula II and an adipic diester of the formula III
ROCO—(CH
2
)
4
—COOR III,
where R is defined as above, is reacted, in particular a mixture as obtained by the process according to DE-A 19 607 954.
The reaction according to the invention can be represented, for example for the conversion of methyl 5-formylvalerate to cyclopentanone and methyl cyclopentene-1-carboxylate, by the following reaction equation.
When 6-hydroxycaproic acid or an ester thereof or a compound which is converted into 6-hydroxycaproic acid or an ester thereof, e.g. &egr;-caprolactone, an additional simultaneous catalytic dehydrogenation is required.
In all cases it was surprising that this reaction proceeded in high yields, selectivities and space time yields.
Starting compounds of formula II are 5-formylvaleric acid and 6-hydroxycaproic acid and esters thereof, alone or as a mixture with adipic diesters, in which case the esters may contain aliphatic radicals having 1-6 carbon atoms or cycloaliphatic, aromatic radicals or araliphatic radicals having 5-12, preferably 6-8, carbon atoms. Examples of radicals R are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, hexyl, cyclopentyl, cyclohexyl, phenyl or benzyl radicals.
Examples of compounds of the formula II which may be used as starting materials include: 5-formylvaleric acid, 6-hydroxycaproic acid, methyl 5-formylvalerate, ethyl 5-formylvalerate, isobutyl 5-formylvalerate, cyclohexyl 5-formylvalerate, benzyl 5-formylvalerate, phenyl 5-formylvalerate, 6-hydroxycaproic acid, methyl 6-hydroxycaproate, propyl 6-hydroxycaproate, n-butyl 6-hydroxycaproate, cyclopentyl 6-hydroxycaproate, phenyl 6-hydroxycaproate, alone or as a mixture with dimethyl adipate, diethyl adipate or di-n-butyl adipate.
It is also possible to use mixtures of compounds of the formula II featuring both formyl and hydroxymethyl groups as starting compounds.
Further possible starting compounds are compounds which are converted into compounds of the formula II under the reaction conditions. For example, mixtures of caprolactone and water or alcohols may be used instead of 6-hydroxycaproic acid or 6-hydroxycaproic esters. If, for example in the reaction of 6-hydroxycaproic esters according to the invention, caprolactone is byproduced, it can be separated off and recycled.
5-Formylvaleric acid to be used as a starting compound may be obtained by hydroformylation of 3- and 4-pentenoic acid, for example as described in WO 97/08127. 5-Formylvaleric esters may be obtained by hydroformylation of 3- and 4-pentenoic esters, for example as described in EP-A 556 681.
6-Hydroxycaproic acid and 6-hydroxycaproic esters are formed, for example, by hydrolysis or alcoholysis of caprolactone.
In a particular embodiment, mixtures of 6-hydroxycaproic esters and adipic diesters are used as obtained, for example, by the processes described in DE-A 19 607 954, in which case further compounds may be present in addition to 6-hydroxycaproic esters and adipic diesters, such as caprolactone, 6-alkoxycaproic esters, glutaric diesters, 5-hydroxyvaleric esters, 2-oxocaproic esters, 1,2-cyclohexanediols, valerolactone, unsaturated adipic diesters, for example dihydromuconic diesters, 3-hydroxypentanoic esters, 4-oxopentanoic esters and 5-oxohexanoic esters. These compounds generally neither adversely affect the reaction according to the invention nor, surprisingly, give rise to a deterioration in product quality after purification by distillation.
The proportion of adipic diester in the mixture to be reacted is typically up to 95, preferably up to 90, % by weight.
Suitable catalysts are acidic or basic catalysts, but also catalysts having both acidic and basic properties. When 6-hydroxycaproic acid or an ester thereof is used as starting compound, the catalysts must also have dehydrogenating properties.
For the purposes of the present invention, oxidic catalysts are not only oxides in the narrow sense but also complex oxygen-containing compounds which have intrinsic acidic or basic properties or may be doped accordingly. Hence it is also possible to use heteropolyacids, for example applied to a carrier, zeolites, which are present in the H-form for acidic activity and which are doped with alkali for basic activity, metal phosphates or compounds such as carbonates or hydroxides which can be converted into oxides.
Examples of oxidic catalysts are oxides of elements of groups 1-14 of the Periodic Table of the Elements or rare earth metal oxides or mixtures thereof. For example, use may be made of alkali metal oxides such as sodium oxide, alkaline earth metal oxides, such as magnesium oxide, calcium oxide, barium oxide, furthermore boron trioxide, aluminum oxide, silicon dioxide, for example in the form of silica gel, fused silica, silicates or quartz, furthermore tin dioxide, bismuth oxide, copper oxide, zinc oxide, lanthanum oxide, titanium dioxide, zirconium dioxide, vanadium oxides, chromium oxides, molybdenum oxides, tungsten oxides, manganese oxides, iron oxides, cerium oxides, neodymium oxides or mixtures thereof. The catalysts may also be modified by applying additives, such as acids (for example phosphoric acids) or bases (for example sodium hydroxide).
Specific examples are La
2
O
3
, ZrO
2′
Cr
2
O
3
/ZrO
2
, CaO/ZnO, MgO/ZnO, K
2
O/TiO
2
, La
2
O
3
/Al
2
O
3
and ZrO
2
—SO
4
.
The heteropolyacids to be used according to the invention contain, as essential element, tungsten or preferably molybdenum, which may be partially replaced by vanadium. If vanadium is used, V:Mo atomic ratios of 1:6-1:12 are preferred. Examples of central atoms are phosphorus, silicon, arsenic, germanium, boron, titanium, cerium, thorium, manganese, nickel, tellurium, iodine, cobalt, chromium, iron, gallium, vanadium, platinum, beryllium and zinc. Phosphorus and silicon are preferred. A preferred ratio of molybdenum or tungsten atoms to the respective central atom is 2.5:1-12:1, preferably 11:1-12:1.
Specific examples
Fischer Rolf
Liang Shelue
Pinkos Rolf
Stein Frank
BASF - Aktiengesellschaft
Keil & Weinkauf
Killos Paul J.
LandOfFree
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