Synthesis of bis(ether nitrile)s and bis(ether acid)s from simple aromatic diols bymeta-fluoro displacement from 3-fluorobenzonitrile

Geoffrey C. Eastmond, Jerzy Paprotny
1997 Journal of Materials Chemistry  
There is interest in synthesizing bis(ether acid)s and related compounds to use as monomers in order to prepare processable aromatic polymers, such as poly(ether amide)s and poly(ether ester)s. We have now found that it is possible to prepare eÃciently bis(3-cyanophenoxy)phenylenes by fluoro displacement from 3-fluorobenzonitrile and phenylene diols or their derivatives, such as substituted catechols, and to convert those bis(ether nitrile)s to bis(3-carboxyphenoxy)phenylenes which can be used
more » ... which can be used in the synthesis of poly(ether amide)s and poly(ether ester)s. The meta-fluoro displacement is performed at elevated temperatures in N-methylpyrrolidinone. Following the development of processable poly(ether imide)s the same substitution pattern, there are nine possible isomers: , opo(X) 2 , etc. I,1 we recently demonstrated that major enhancement in processability can be achieved by modifying the substitution Where substitution patterns of the terminal rings are para or ortho, formation of the ether linkages by aromatic nucleo-pattern of the aromatic unit Ar between the ether linkages in I, especially by inclusion of 1,2-linked units derived from philic displacement (S N Ar) reactions between a diol (to form the central ring) and a suitably activated nitro-or halo-benzene catechol or substituted catechols.2 It is logical to extend these concepts to the synthesis of poly(ether amide)s and poly(ether (Scheme 1) is easily achieved; Evers et al.5 used chloro displacement reactions while we used fluoro displacement.3 In these ester)s to achieve similar improvements in processability over conventional aromatic polyamides.3 reactions an activating group X may be a precursor of a desired X in structures II. Thus, MCN or MNO 2 groups are activating groups and are also precursors to MCOOH and MNH 2 , respectively. The leaving group Y is preferably NO 2 or F and is strongly activated if it is ortho-or para-to X. In this way we have prepared a variety of popX 2 and oooX 2 bis(ether acid)s and bis(ether amine)s from catechol and substituted catechols and have used these in the synthesis of poly(ether amide)s and poly(ether ester)s.3 These syntheses are relatively trivial. pop(CN) 2 and pop(COOH) 2 have also recently been prepared by others and used in the synthesis of poly(ether amide)s.7,8 A problem has been to prepare such materials in which the substitution pattern in the outer rings is meta, e.g. as mpmX 2 , mmmX 2 or momX 2 , eÃciently because, according to the rules of S N Ar reactions, if Y is meta to X it is not suÃciently activated to leave. Evers et al. recognised this problem and synthesized mpm(COOH) 2 by a two-stage process, reacting the sodium salt of meta-cresol with dibromobenzenes in pyridine To achieve this end, poly(ether amide)s can be prepared in the presence of copper() chloride and oxidizing the resulting from either/or both bis(ether acid)s or bis(ether amine)s of dialkyl species with potassium permanganate in pyridine to structure II, with diÂerent substitution patterns at each aroobtain the diacid in 38% overall yield.5 Synthesis of the matic residue. Thus, the synthesis of substances with structure mpm(CN) 2 was a five-stage synthesis with a yield of 8.5%. II is of interest. A number of bis(ether nitrile)s IIa, used in We have now demonstrated that, when X is MCN, metapoly( benzoxazole) synthesis,4 bis(ether acid)s IIb, a bis(ether fluoro displacement is easily achieved in high yield according acid chloride) IIc5 and a bis(ether amine) IIc6 have long been to Scheme 2 at elevated temperatures when fluorobenzonitrile known. Evers et al.5 used an aromatic nucleophilic displace-III is reacted, under suitable conditions, with a diol IV ment reaction between p-chlorobenzonitrile and various diols (Table 1) . Thus, mom(CN) 2 -type bis(ether nitrile)s become to prepare bis(ether nitrile)s directly, some of which were immediately available and, after hydrolysis, bis(ether acid)s of hydrolysed to the bis(ether acid)s. Thus, Evers et al. prepared bis(ether nitrile)s and bis(ether acid)s and devised a nomenclature based on the substitution patterns of the rings, e.g. ppp(COOH) 2 , pop(COOH) 2 .5 We have adapted this system to allow for substituents on the rings, thus we have, for example, p(3Me)op(COOH) 2 for the diacid in which the terminal rings are para-linked and unsubstituted while the central ring is ortho-linked and carries a 3-methyl substituent. For unsubstituted species II which are symmetrical, i.e. the outer rings have
doi:10.1039/a701127j fatcat:nhsfvc3uvrasjcj7km6jz2f4gy