Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Reexamination Certificate
2001-03-30
2003-04-08
Wong, Edna (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
Reexamination Certificate
active
06544390
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to “microwave assisted rapid and economical process for the preparation of substituted phenylaldehydes from trans and toxic cis-phenylpropenes: a commercial utilization of toxic cis-isomer” in which industrially important phenylaldehydes (e.g. asaronaldehyde where R
1
is CHO, R
2
═R
4
═R
5
is —OMe and R
3
═R
6
is H; p-anisaldehyde where, R
1
is —CHO, R
2
═R
3
═R
5
═R
6
is H and R
4
is —OMe and vetralaldehyde where R
1
is —CHO, R
2
═R
5
═R
6
is H; R
3
═R
4
is —OMe or the like) of the formula I
are obtained via oxidation of easily available isomeric forms (trans and cis-isomer) of (R
2
—R
3
—R
4
—R
5
—R
6
)phenylpropene bearing essential oils (i.e. &bgr;-asarone, anethole, and methyl isoeugenol or the like) wherein R
2
to R
6
equal or different, being hydrogen or hydroxy or acyl or alkyl or methylenedioxy or alkoxy groups or the like, under microwave irradiation using meta-periodate/osmium tetraoxide (catalytic amount) for a reaction time less than 20 minutes in biphasic system comprising a solvent and aqueous phase containing a catalyst (such as quaternary ammonium salt and amberlite IRA-410 etc) with high yield varying from 71-82% depending upon the reagent, reaction time, condition and the phenylpropene used. In addition crude
Acorus calamus
oil (rich in &bgr;-asarone present in 70-94%) used directly for microwave assisted oxidation is an added benefit as remaining constituents of
calamus
oil do not interfere for the preparation of asaronaldehyde (yield just less by 5-10% depending upon asarone percentage in
calamus
oil) which makes the above process further cost effective since tetraploid and hexaploid varieties of
Acorus calamus
has been internationally banned for their use in human consumption. Moreover, we have observed that the preparation of asaronaldehyde (a versatile drugs precursor) requires lesser time (2-20 minutes) under microwave irradiation while oxidation takes 2-6 hours when conducted at room temperature (conventional method).
BACKGROUND OF THE INVENTION
Naturally occurring substituted phenylaldehydes (Harborne, J. B. and Baxter, H., In: Phytochemical Dictionary, A Handbook of Bioactive Compounds from Plants, Taylor & Francis Ltd., London WC1N 2ET, 472-488 (1993)) e.g. vanillin, p-anisaldehyde, p-hydroxybenzaldehyde, asaronaldehyde, heliotropin and vetralaldehyde etc possess in common an aromatic ring bearing one or more hydroxy or dioxymethylene or alkoxy groups or the like, attached to a aldehyde group (CHO) contribute significantly to the taste and flavour of many foods, drinks, perfumery and serve as a pharmaceutical aid. In addition, phenylaldehyde derivatives serve as a raw material for the preparation of a large number of aromatic compounds useful in the perfume industry e.g. treatment of phenylaldehyde with alkali alcoholate results in the formation of phenyl benzoate and condensation of phenylaldehyde derivative with acetaldehyde gives cinnamic aldehyde which are useful in both the perfume and pharmaceutical industries. In addition, large quantities of phenylaldehydes are used in the manufacture of dyes, medicines (Patel, P. J.; Messer Jr., W. S. and Hudson, R. A., J. Med. Chem., 36, 1893-1901 (1993)), photographic films, cosmetics, dyes, agrochemicals etc.
The widespread aromatic aldehydes such as vanillin is obtained from the pods of
Vanilla planifolia
(family: Orchidaceae), the bulbs of Dahlia spp. (Compositae), the sprouts of Asparagus spp. (Liliaceae), the beats of Beta spp. (Chenopodiaceae) and also from the essential oils of
Syzygium aromaticum
(Myrtaceae), Ruta spp. (Rutaceae), Spiraea spp. (Rosaceae) and Gymnadenia spp. (Orchidaceae), while 3,4-methylenedioxybenzaldehyde (heliotropin) is obtained from the essential oils of the flowers and leaves of
Robinia pseudacacia
(Legumminosae),
Doryphora sassafras, Eryngium potericum
(Umbelliferae), Heliotropium spp. (Boraginaceae), Vanilla spp. (Orchidaceae) and from extracts of Viola spp. (Violaceae) and
Baccharis rosmarinifolia
(Compositae). Other phenylaldehydes are restricted to a few families such as p-anisaldehyde occurs in the fruits of
Pelea madagascariensis
(Rutaceae),
Agastache rugosa
(Labiatae), leaves of
Magnolia salicifolia
(Magnoliaceae) and also in the essential oils of Vanilla spp. (Orchidaceae), Acacia spp. (Leguminosae), Cassia spp. (Leguminosae), Pinus spp. (Pinaceae),
Pimpinella anisum
(Umbelliferae),
Illicium verum
(Illiciaceae), whereas p-hydroxybenzaldehyde occurs in traces in
Plocama pendula
(Rubiaceae),
Pterocarpus marsupium
(Leguminosae), and asaronaldehyde in the essential oils of Acorus spp. (Motley, T. J., Economic Botany, 48: 397-412, (1994) and Piper spp. (Koul, S. K., Taneja, S. C., Malhotra, S. and Dhar, K. L., Phytochemistry, 32(2): 478-480, (1993)). However, the limited percentage of these substituted phenylaldehydes present in the plant kingdom is not sufficient to fulfill the world demand and as a result, the major amounts of phenylaldehydes are made synthetically.
A number of processes have been proposed to prepare substituted phenylaldehydes such as p-anisaldehyde, dimethoxybenzaldehyde, vanillin, heliotropin, asaronaldehyde etc. For the most part, these methods involves reacting the substituted benzene, such as p-methoxybenzene, 1,2,4-trimethoxybenzene with freshly distilled phosphorus oxychloride (POCl
3
) in the presence of anhydrous N,N-dimethylformamide (DMF). However, while this Vilsmeier-Haack method has been proven to be useful, they suffer from one or more process deficiencies. For example, some processes of this type necessarily involve resort to sub ambient temperatures, which, of course, involves some considerable process control. In addition, large excesses of DMF and POCl
3
must necessarily be employed to carry out the synthesis to obtain appreciable yields and moreover, POCl
3
give rise to a violent exothermic reaction leading to obvious problems. Lastly, in some cases, the reaction is effected by the formation of some side reaction products (Toril, S., Uneyama, K. and Ueda, K., J. Org. Chem., 49, 1830-1832 (1984).
Typical prior art refrences include U.S. Pat. Nos. 2,794,813; 5,358,861; 3,799,940; European Patent No. EP-A 405,197; Japanese Pat. Nos. 10,754,442A2; 55,87, 739; British Pat. Nos. 417,072; 774,608; 1,092,615; U.S.S.R. Pat. No. 490,793 and German Pat. Nos. 57,808; 207,702.
It therefore becomes an object of the invention to provide rapid and economical process for the preparation of substituted phenylaldehydes from trans and cis-phenylpropenes which further provide commercial utilization of toxic cis-isomer as well as eliminate the above discussed disadvantages and others.
OBJECTIVES OF THE INVENTION
The main object of the present invention is to develop a rapid and economical process for the preparation of useful phenylaldehydes (such as p-methoxybenzaldehyde, vetralaldehyde, asaronaldehyde etc) in one step.
Another object of the invention is to develop a simple process for the preparation of phenylaldehyde in high purity.
Another object of the invention is to develop a simple process for the preparation of phenylaldehyde with minimum or no side product formation such as corresponding acid.
Yet another object of the invention is to develop an easy work-up of the reaction product.
Yet another object of the invention is to develop a simple process for high degree of conversion.
Yet another object of the invention is to develop a process, which does not require anhydrous reaction medium, a condition preferred by industries.
Yet another object of the invention is to develop a simple process which does not require explosive and expensive reagents, hence, capable of undergoing commercial scale production.
Yet another object of the invention is to develop a simple and quick process for the preparation of substituted phenylaldehydes in a short time ranging from 2 to 20 minutes under microwave irradiation.
Yet another object of the invention is to develop a process for the preparation of value added produ
Dogra Ruchi
Joshi Bhupendra Prasad
Sinha Arun Kumar
Council of Scientific & Industrial Research
Jordan and Hamburg LLP
Wong Edna
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