Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1991-10-02
1993-05-25
Dees, Jose G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
560138, 560139, 560142, C07C 6700
Patent
active
052141926
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the preparation of iodo compounds and more specifically to the preparation of diacetoxyiodoarene compounds.
Diacetoxyiodoarene compounds are examples of polyvalent iodo compounds that have specific practical uses in organic syntheses, acting for example by way of ligand exchange or as specific oxidants.
When commercial scale activities are contemplated, it is generally recognised that in an ideal world, it would be advantageous to employ reactants, for example oxidising systems that were not only widely available, storage stable, easy to handle and relatively cheap, but would also perform the desired reaction under mild conditions.
It is an object of the present invention to provide a process for the preparation of diacetoxyiodoarene compounds that employs widely available and relatively cheap reagents and which can be carried out under relatively mild conditions.
According to the present invention, there is provided a process for the preparation of an diacetoxyiodoarene compound in which an iodoarene compound is brought into contact with an excess of alkali metal perborate and acetic acid at a mild temperature and permitted to react until at least a proportion of the iodoarene has been oxidised to the corresponding diacetoxyiodoarene.
The iodo arene can be otherwise unsubstituted or be substituted by one or more of a wide range of substituents, which can be either electron donating or electron withdrawing, provided that the latter is meta to the iodo group. It will be understood that electron-withdrawing substituents in either the ortho or para position significantly inhibit the instant invention process. When two or more substituents are present, they can be the same as each other or different. Provided that the foregoing constraint is taken into account, the or each substituent can be chosen from halo, nitro, carboxylic acid, nitrile, alkyl or alkoxy substituents. The halo group can be a fluoro, chloro, bromo or iodo group, and the alkyl substituent preferably contains only a small number of carbon atoms. It will be recognised that if certain other substituents are present, such as an aldehyde, they will also, possibly preferentially, be oxidised under the conditions of the present invention, so that the substrate is oxidised at two substituents. It will be recognised that where a substituent is oxidisable under the conditions of the present invention, the reaction will be influenced not only by the the electron-withdrawing or donating nature of the sutstituent itself, but also by that of the corresponding oxidised substituent. Thus, for example, the reaction product of an aldehyde substituent is a carboxylic acid substituent, and accordingly irrespective of whether there would be any constraints imposed by virtue of the aldehyde itself, the nature of its oxidation product means that it can be present only in the meta position to the iodo substituent.
In many instances the arene nucleus is benzene, although di or polycyclic nuclei are also suitable
It will also be understood from the foregoing since iodo is a halo group that it is possible for the arene nucleus to be substituted by two or more iodo groups, in any positions around the nucleus. Naturally, though, constraints applicable to the positioning of any substituent relative to an iodo group are applied in respect of each iodo group
Advantageously, provided that the substituents are suitably chosen position-wise in accordance with their electron donating or withdrawing nature, there appears to be no significant restriction on the number of substituents around the arene nucleus, other than the number of available carbon atoms in the nucleus. Thus, for example, up to four substituents in addition to the iodo substituent can easily be contemplated around a benzene nucleus, if desired
The alkali perborate is particularly conveniently a sodium perborate on account of its bulk availability and excellent storage and handling properties of the two industrially available products sodium perborate monohydrate and sodium perbo
REFERENCES:
patent: 3644486 (1972-02-01), Boldt et al.
patent: 3772383 (1973-11-01), Kominami et al.
patent: 3887608 (1975-06-01), Kominami et al.
Kemp Duncan
McKillop Alexander
Clarke Vera C.
Dees Jos,e G.
Interox Chemicals Limited
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