Preparation of cyclic lactams

Details Preparation of cyclic lactams Preparation of cyclic lactams

2002-10-17

2004-01-27

Kifle, Bruck (Department: 1624)

Organic compounds -- part of the class 532-570 series

Organic compounds

Unsubstituted hydrocarbyl chain between the ring and the -c-...

Reexamination Certificate

active

06683178

ABSTRACT:

SUMMARY
A process for the preparation of cyclic lactams of formula (II)
in which n and m may individually have the value 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 and the sum of n and m is at least 3 and preferably at least 4 and R
1
and R
2
denote C
1
-C
6
alkyl, C
5
-C
7
cycloalkyl or C
6
-C
12
aryl groups
by the reaction of a compound (I) of the formula
in which R
1
, R
2
, m and n have the meanings stated above and R de-notes nitrile, carboxamide and carboxylic acid groups,
with water in the presence of an organic liquid diluent in the liquid phase, wherein
a) compound (I) is caused to react with water in the liquid phase in the presence of an organic liquid diluent (III) to form a mixture (IV) containing a lactam (II), the diluent (III) having a miscibility gap with water under certain conditions of concentration, pressure and temperature,
b) mixture (IV) is subjected, before or after separation of ammonia, to conditions of concentration, pressure and temperature under which diluent (III) and water are present in the liquid state and exhibit a miscibility gap, to give a two-phase system comprising a phase (V) in which the content of diluent (III) is higher than that of water and a phase (VI) in which the content of water is higher than that of diluent (III),
c) phase (V) is separated from phase (VI), and
d) from phase (V) diluent (III) and optionally by-products comprising low boilers, high boilers and/or unconverted compound (I) are separated, to give lactam (II).
DESCRIPTION
The present invention relates to a process for the preparation of cyclic lactams of formula (II)
in which n and m may individually have the value 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 and the sum of n+m is at least 3 and preferably at least 4, and R
1
and R
2
denote C
1
-C
6
alkyl, C
5
-C
7
cycloalkyl or C
6
-C
12
aryl,
by the reaction of a compound (I) of the formula
in which R
1
, R
2
, m and n have the meanings stated above and R denotes nitrile, carboxamide and carboxylic acid groups,
with water in the presence of an organic liquid diluent in the liquid phase, wherein
a) compound (I) is caused to react with water in the liquid phase in the presence of an organic liquid diluent (III) to form a mixture (IV) containing a lactam (II), the diluent (III) having a miscibility gap with water under certain conditions of concentration, pressure and temperature,
b) mixture (IV) is subjected, before or after separation of ammonia, to conditions of concentration, pressure and temperature under which diluent (III) and water are present in the liquid state and exhibit a miscibility gap, to give a two-phase system comprising a phase (V) in which the content of diluent (III) is higher than that of water and a phase (VI) in which the content of water is higher than that of diluent (III),
c) phase (V) is separated from phase (VI), and
d) from phase (V) diluent (III) and optionally by-products comprising low boilers, high boilers and/or unconverted compound (I) are separated, to give lactam (II).
Processes for the preparation of cyclic lactams by reaction of &ohgr;-aminocarboxylic derivatives with water in the presence of a heterogeneous catalyst and an organic liquid diluent in the liquid phase are well known, for example the preparation of caprolactam from 6-aminocarboxynitrile.
Thus WO 95/14665 and WO 95/14664 disclose that it is possible to cause 6-aminocapronitrile to react in the liquid phase with water in the presence of heterogeneous catalysts and a solvent to form caprolactam and ammonia. The highest caprolactam yields (from 86 to 94%) are attained using titanium(IV) oxide as catalyst and ethanol as solvent. The caprolactam yields were determined only by gas chromatography and workup of the effluents to produce crude and/or pure caprolactam is not described.
WO 97/23454 describes, in Example 1C), the reaction of 6-aminocapronitrile with water in the presence of titanium(IV) oxide and ethanol. Caprolactam was obtained from the effluent by fractional distillation in a yield of 80%.
A disadvantage of the said conversion of 6-aminocapronitrile to caprolactam in the presence of ethanol is that the caprolactam yields are low. The yield losses occurring during workup are not indicated.
It is thus an object of the present invention to provide a process which allows for the preparation of cyclic lactams (II) from compounds (I) in an industrially simple and economical manner to give high conversions of compound (I) and high lactam yields and minimizes yield losses during the purification stage.
Thus we have found the process defined above.
Suitable compounds (I) are amino acids and their derivatives, preferably those of the general formula I
in which R denotes a carboxylic acid group, a nitrile group and/ or a carboxamide group and n and m independently have a value of 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 and the sum of n+m is at least 3 and preferably at least 4.
R
1
and R
2
can be theoretically substituents of any type, the only proviso being that the desired cyclization reaction may not be influenced by the substituents. R
1
and R
2
are preferably independently C
1
-C
6
alkyl or C
5
-C
7
cycloalkyl or C
6
-C
12
aryl groups.
Particularly preferred starting compounds are aminocarboxynitriles, preferably of the general formula
H
2
N—(CH
2
)
m
—C≡N
in which m has a value of 3, 4, 5 or 6 and particularly 5. When m is 5, the starting compound is 6-aminocapronitrile.
The compound (I) used can be an individual compound (I) or a mixture of different compounds (I). Preferably compound (I) is used as an individual compound.
&ohgr;-Aminocarboxynitriles are obtained, for example, by partial hydrogenation of &agr;, &ohgr;-dinitriles in the vapor or liquid phase, eg as described in WO 96/20166, WO 96/20916 or WO 96/20165.
&ohgr;-Amino acids are obtained, for example, by hydroamination of &ohgr;-formylcarboxylic acids or by hydrolysis of &ohgr;-aminocarboxylates or &ohgr;-aminocarboxynitriles.
&ohgr;-Amino acids are obtained, for example, by hydroamination of &ohgr;-formylcarboxylic acids or hydrolysis of &ohgr;-aminocarboxylates or &ohgr;-aminocarboxynitriles.
In the process of the invention there are obtained, depending on compound (I), the corresponding cyclic lactams of formula (II)
in which n, m, R
1
and R
2
have the meanings stated above. Particularly preferred lactams are those in which n is equal to 0 and m has a value of 3, 4, 5 or 6. When m is 5, the product is caprolactam.
In the process of the invention the compound (I) described above is caused to react, in step a), with water in the liquid phase, preferably in a homogeneous liquid phase, advantageously in the presence of a heterogeneous catalyst and an organic liquid diluent (III), to form a mixture (IV) containing a lactam (II), the diluent (III) exhibiting a miscibility gap with water under certain conditions of concentration, pressure and temperature.
Suitable heterogeneous catalysts are acid, basic or amphoteric oxides of Group IIa, Group IIIa or Group IVa elements, such as calcium oxide, magnesium oxide, boron oxide, aluminum oxide, tin oxide or silicon dioxide as pyrogenically prepared silicon dioxide, as silica gel, kieselguhr, quartz or mixtures thereof, also oxides of Group IIb to Group VIb metals, such as amorphous titanium(IV) oxide as anatase or rutile, zirconium dioxide, manganese oxide or mixtures thereof. Also useful are oxides of the lanthanoids and actinides, such as cerium oxide, thorium oxide, praseodymium oxide, samarium oxide, rare-earth mixed oxide, or mixtures thereof with the above oxides. Examples of further catalysts are:
vanadium oxide, barium oxide, zinc oxide, niobium oxide, iron oxide, chromium oxide, molybdenum oxide, tungsten oxide or mixtures thereof.
Mixtures of said oxides with each other are likewise possible. In addition, some sulfides, selenides and tellurides such as zinc telluride, tin selenide, molybdenum sulfide, tungsten sulfide, and sulfides of nickel, zinc and chromium can be used.
The aforementioned compounds can be doped with, or contain, Group 1a compounds and Group 7a compounds.
Examples of other su

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