Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-01-25
2002-02-05
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S403000, C562S405000, C562S428000
Reexamination Certificate
active
06344585
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to a process for the preparation of raw materials for various resins or intermediates for various chemical products, and more specifically to a process for the industrially advantageous high-yield production of fluorenes as raw materials for epoxy resins, raw materials for function resins such as polycarbonates or polyesters, or raw materials for pharmaceutical products such as anticancer agents from economical raw materials while producing at the same time other compounds useful as various chemical products. It is to be noted that the term “fluorenes” as used herein means fluorene itself and fluorene derivatives having substituent group(s) and position isomers (this definition equally applies to other compounds).
b) Description of the Related Art
Processes heretofore known for the provision of fluorenes include those relying upon their separation and purification from coal tar and those featuring their synthesis. Collection of these compounds, especially as high-purity products, from coal tar is not considered to be an advantageous approach in view of both of technical difficulties and cost, because basically, their contents in coal tar are extremely low.
On the other hand, the known processes for obtaining fluorenes by synthesis include a process involving dehydrocyclization of an alkylbiphenyl compound (U.S. Pat. No. 3,325,551), a process making use of dehydrogenation coupling of a diphenylmethane (PCT/WO 97/17311), and a process relying upon a Pschorr reaction of an o-(1-methylphenyl)aniline [(Ibuki et al., YAKUGAKU ZASSHI, 100(7), 718 (1980))].
Nonetheless, none of the raw material compounds employed in these processes are readily available at low price. Reasons for this problem are postulated to include inter alia: 1) these raw materials themselves are also obtained from coal tar components and hence, require separation and purification; 2) the purified products have to be incorporated in synthesis steps; and 3) the raw material compounds have to be obtained by synthesis. Irrespective of the process, many preparation steps are needed for the provision of a target fluorene. Accordingly, the industrially disadvantageous situation of these synthesis processes cannot be negated.
Incidentally, a process is widely known for the synthesis of a tetrahydrofluorene. According to this process, an indene is subjected as a dienophile together with a butadiene to a Diels-Alder reaction. This synthesis process can readily synthesize fluorenes, each of which contains one or more substituent(s) at particular position(s), by making combined use of dienes and dienophiles having various substituents, respectively, and is considered to be very useful process from the industrial standpoint. Further, dehydrogenation of such tetrahydrofluorenes in the presence of a catalyst can lead to their corresponding fluorenes.
The above-described dehydrogenation can synthesize fluorene with a yield of 90% by reacting tetrahydrofluorene at 250° C. for 5 hours in the presence of a dehydrogenation catalyst such as PD/C. Other tetrahydrofluorenes can also be synthesized into the corresponding fluorenes with yields around 90% under similar reaction conditions. This conventional process, however, requires concentration of a tetrahydrofluorene from a Diels-Alder reaction mixture of the corresponding indene and butadiene by a method such as distillation. Moreover, the dehydrogenation reaction has to be conducted for a time as long as 5 hours or more if one wants to increase the yield of the fluorene. This, however, has developed another problem that the raw materials are partially lost due to polymerization.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide a process capable of advantageously preparing a fluorene useful as an intermediate for various synthesized organic products and also as a raw material for various resins while preparing another useful compound at the same time.
The above-described object can be achieved by the present invention to be described hereinafter. Namely, the present invention provides a process for the preparation of a fluorene, which comprises subjecting a tetrahydrofluorene, which is represented by the following formula (I)
wherein R
1
to R
6
each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, or R
1
and R
2
are combined together to represent ═O, ═N or ═S, R
7
and R
8
each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a hydroxyl group or a carboxyl group, to a hydrogen transfer reaction in the presence of a hydrogen acceptor and a catalyst, whereby the fluorene and a hydride of the hydrogen acceptor are formed at the same time.
When a fluorene is formed in a hydrogen transfer reaction from a tetrahydrofluorene obtained, for example, by a Diels-Alder reaction, hydrogen is theoretically released from the tetrahydrofluorene. According to the present invention, the hydrogen transfer reaction is conducted in the presence of the hydrogen acceptor. The transfer of hydrogen from the tetrahydrofluorene to the hydrogen acceptor is allowed to proceed almost completely, so that the corresponding fluorene and the corresponding hydride of the hydrogen acceptor are formed with high yields. In addition, the process of the present invention can prepare the fluorene in a shorter time than the conventional dehydrogenation reactions.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The present invention will next be described more specifically based on preferred embodiments.
The tetrahydrofluorene of the formula (I) for use in the present invention may be collected or synthesized by any process known to date, and no particular limitation is imposed on the tetrahydrofluorene. It is, however, preferred to synthesize it by a Diels-Alder reaction which makes use of an indene of the following formula (I) and a butadiene of the following formula (III):
wherein R
1
to R
8
have the same meaning as defined above in connection with the formula (I).
In the present invention, it is preferred to obtain the tetrahydrofluorene by the Diels-Alder reaction. Examples of the indene for use in the reaction can include alkylindenes such as indene, methylindene and ethylindene; indanone; and thioindanone. Examples of the butadiene for use in the present invention, on the other hand, can include butadiene, isoprene, 2,3-dimethylbutadiene, chloroprene, 2-hydroxy-1,3-butadiene and 2-methoxy-1,3-butadiene.
The indene and butadiene, which are raw materials, are desirably free of chemical species detrimental to the Diels-Alder reaction, namely, other diene species and dienophiles. The purities of the raw materials are practically immaterial insofar as their impurities do not impair the Diels-Alder reaction. In this case, it is unnecessary to purify the raw materials in advance.
The butadiene for use in the Diels-Alder reaction is used in a smaller amount than the indene in terms of molar ratio. For example, it is preferred to use the butadiene in a proportion of from 0.1 to 0.5 moles per mole of the indene. Use of the butadiene in a proportion lower than the above-described range leads to a problem in that the productivity of the tetrahydrofluorene as the target compound will be unduly low although its yield will be good based on the used butadiene. Use of the butadiene in a proportion beyond the above-described range results in occurrence of many side reactions, leading to a problem in that the yield of the target product will be low based on the used butadiene.
In the Diels-Alder reaction, a catalyst may be added or may not be added. Usable examples of the catalyst can include metal halides such as aluminum chloride, boron trifluoride, titanium chloride, cobalt chloride, vanadium chloride, chromium chloride, manganese chloride, iron chloride, nickel chloride, copper chloride, zinc chloride and tin chloride; metal sulfides; metal su
Adchemco Corporation
Killos Paul J.
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