Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-12-20
2004-05-11
Lambkin, Deborah C. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C548S453000
Reexamination Certificate
active
06734312
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for preparing a heteroaromatic compound having a heteroaromatic nucleus substituted with one or more ether groups.
BACKGROUND OF THE INVENTION.
Polythiophenes and polypyrroles have been studied extensively due to their interesting electrical and/or optical properties (see Handbook of Conducting Polymers, Eds. Skotheim, T. A.; Elsenbaumer, R. L.; Reynolds, J. R., Marcel Dekker, New York, 1998, 2nd edition). Within these classes of electroconductive polymers, poly(3,4-alkylenedioxythiophenes) and poly(3,4-alkylenedioxypyrroles) have particularly useful electrical and/or optical properties. Poly(3,4-ethylenedioxythiophene) [PEDOT] in association with the polyanion poly(styrene sulfonic acid) [PSS] is one of the most commercially successful conductive polymers in the world. It is being used in a wide variety of applications as described by L. Groenendaal et al. in 2000 in Advanced Materials, volume 12, pages 481-494.
Two routes for preparing the monomers from which poly(3,4-alkylenedioxythiophenes) and poly(3,4-alkylenedioxypyrroles) are prepared, 3,4-alkylenedioxythiophenes, such as 2,3-dihydro-thieno [3,4-b][1,4]dioxine [also known as 3,4-ethylenedioxythiophene (EDOT)], and 3,4-alkylenedioxypyrroles have been disclosed: via a double Williamsson synthesis [see Pei et al. in 1994 in Polymer, volume 35, pages 1347-1351, for thiophene derivatives, and J. R. Reynolds et al. in 2001 in Journal of Organic Chemistry, volume 66, pages 6873-6882, and A. Merz et al. in 1995 in Synthesis, pages 795-800, for pyrrole derivatives], via the alkylation procedure reported by Halfpenny et al. in 2001 in Journal Chemistry Society, Perkins Transaction I, pages 2595-2603 who modified the alkylation procedure reported by Dallacker and Mues in 1975 in Chemische Berichte, volume 108, page 576 by using 1,2-bromoethane instead of bromochloromethane, and via transetherification of 3,4-dimethoxythiophene (see Reynolds et al in 1999 in Advanced Materials, volume 11, pages 1379-1382).
The double Williamson route and the alkylation procedure suffers from the disadvantages that it mostly uses &agr;,&ohgr;-dichloro- or &agr;,&ohgr;-dibromo-alkanes, which with short chain alkanes such as ethane or propane are extremely toxic, for the ring closure and that substituted derivatives (at the 2-position of the dioxine ring) are, if obtainable, only obtainable in low to very low yields.
The transetherification route has the disadvantages of involving the difficult and expensive synthesis of 3,4-dimethoxy-derivatives (not commercially available) and the low yields for reactions involving secondary alcohol groups. Furthermore, it is not possible to use this reaction for the preparation of pyrrole derivatives.
There is therefore a need for an alternative process for preparing 3,4-alkylenedioxythiophenes and 3,4-alkylenedioxypyrroles avoiding the above-mentioned problems.
OBJECTS OF THE INVENTION
It is therefore an aspect of the present invention to provide a process for preparing 3,4-alkylenedioxythiophenes and 3,4-alkylenedioxypyrroles in high yields, avoiding expensive and toxic intermediates.
Further aspects and advantages of the invention will become apparent from the description hereinafter.
SUMMARY OF THE INVENTION
It has been surprisingly found that the Mitsunobu reaction can be used to prepare a heteroaromatic compound having a heteroaromatic nucleus substituted with one or more ether groups at &agr;- or &bgr;-positions with respect to a heteroatom of the heteroaromatic nucleus, whereas the Mitsunobu reaction is typically used for condensing alcohols with an acidic compound (H—Nu) such as oxygen nucleophiles for example carboxylic acids and phenols; nitrogen nucleophiles for example imides, hydroxamates, and heterocycles; sulfur nucleophiles for example thiols and thioamides; and carbon nucleophiles for example &bgr;-ketoesters.
Aspects of the present invention have been realized by a process for preparing a heteroaromatic compound having a heteroaromatic nucleus substituted with one or more ether groups comprising the step of: condensing at least one hydroxy-group of a compound having the heteroaromatic nucleus, the at least one hydroxy group (—OH) being substituted at &agr;- or &bgr;-positions with respect to a heteroatom of the heteroaromatic nucleus, with an alcohol containing one or more primary or secondary alcohol groups, optionally substituted with nitro, amide, ester, halogen, cyano or (hetero)aromatic groups using the redox couple of a triaryl- or trialkylphosphine and an azodioxo-compound at a temperature between −40° C. and 160° C. The heteroaromatic nucleus for the above-disclosed heteroaromatic compound and the above-disclosed compound are identical.
Further advantages and embodiments of the present invention will become apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
By a heteroaromatic nucleus is meant a heteroaromatic ring comprising carbon and non-carbon atoms with no substituents other than hydrogen atoms.
Substituted at the _&agr;-position relative to a heteroatom of a heteroaromatic nucleus means substituted at a carbon atom directly adjacent to a heteroatom of a heteroaromatic nucleus. There are two &agr;-positions relative to a heteroatom of a heteroaromatic nucleus either side of the heteroatom.
&bgr;-position relative to a heteroatom of a heteroaromatic nucleus means substituted at a carbon atom directly adjacent to the &agr;-position relative to a heteroatom in a heteroaromatic nucleus. There are two &bgr;-positions relative to a heteroatom of a heteroaromatic nucleus on the non-heteroatom side of each of the two &agr;-positions relative to a heteroatom in the heteroaromatic nucleus.
The Mitsunobu reaction is the condensation reaction of alcohols with an acidic compound (H—Nu) using the redox couple of a triaryl- or trialkylphosphine and an azodioxo-compound in which the triaryl- or trialkylphosphine is oxidised to the corresponding phosphine oxide and the azodioxo-compound is reduced to the corresponding hydrazine, as described in Organic Reactions 1992, Vol. 42, 335-656 (Chapter 2 entitled “The Mitsunobu reaction” by D. L. Hughes), and Organic Preparations and Procedures International, 1996, Vol. 28(2), 127-164 (“Progress in the Mitsunobu Reaction. A Review” by D. L. Hughes).
The term alkyl means all variants possible for each number of carbon atoms in the alkyl group i.e. for three carbon atoms: n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl and t-butyl; for five carbon atoms: n-pentyl, 1,1-dimethyl-propyl, 2,2-dimethylpropyl and 2-methyl-butyl etc.
A chiral compound is a compound containing a chiral centre. A chiral centre is an atom, e.g. a carbon atom, that is attached to four different groups. A compound containing a chiral centre is not superimposable upon its mirror image and will exhibit chirality, chirality being the handedness of an asymmetric molecule. Such compounds, if isolated in a pure state, will generally exhibit rotation of polarized light detectable with a polarimeter.
Bu represents an n-butyl group.
Ph represents a phenyl group.
Process for Preparing a Compound Containing a Heteroaromatic Nucleus Substituted With one or More Ether Groups
According to the present invention, a process for preparing a heteroaromatic compound having a heteroaromatic nucleus substituted with one or more ether groups comprising the step of: condensing at least one hydroxy-group of a compound having said heteroaromatic nucleus, said at least one hydroxy group (—OH) being substituted at &agr;- or &bgr;-positions with respect to a heteroatom of said heteroaromatic nucleus, with an alcohol containing one or more primary or secondary alcohol groups, optionally substituted with nitro, amide, ester, halogen, cyano or (hetero)aromatic groups, using the redox couple of a triaryl- or trialkylphosphine and an azodioxo-compound at a temperature between −40° C. and 160° C.
According to a first aspect of the
Groenendaal Bert
Madrigal Luis
Reynolds John R.
Zong Kyukwan
Agfa-Gevaert
Lambkin Deborah C.
Leydig , Voit & Mayer, Ltd.
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