Pyrimidine compounds

Details Pyrimidine compounds Pyrimidine compounds

1997-09-25

1999-11-16

Ford, John M.

Organic compounds -- part of the class 532-570 series

Organic compounds

Nitrogen attached directly or indirectly to the purine ring...

544335, 25229962, C07D23940, C09K 1932

Patent

active

059860960

DESCRIPTION:

BRIEF SUMMARY
This invention relates to pyrimidine containing compounds.
Pyrimidine is generally referred to as a heterocycle and has the following structure: ##STR1##
Pyrimidine occurs in a large number of natural products.
Pyrimidine containing compounds and derivatives of pyrimidine containing compounds are used in a broad range of applications throughout the chemical and other industries. There are various synthetic methods which are used in order to incorporate pyrimidine into target molecules.
The synthesis of many chemical compounds is a long and arduous business. Research chemists are continually looking for ways in which to improve the ease of synthesis and subsequent yields and to synthesise new compounds.
One area in particular in which the incorporation of a pyrimidine ring into a target molecule has received much attention is in liquid crystal chemistry.
There are a number of known liquid crystal systems which contain one or more pyrimidine rings.
Some of the many examples include the phenyl-pyrimidines described in WO 86/00083, which describes a series of optically active liquid crystal compounds that contain the chiral group: ##STR2## where X represents Cl, CN or CH.sub.3 and R.sub.1 and R.sub.2 represent the residue of the molecule. All of the compounds described necessarily contain the phenyl-pyrimidine group on the mesogenic unit.
The difluoro-phenyl pyrimidines described in European Patent Application EP 0 332 024 A1: ##STR3## including those compounds where R.sub.1 and R.sub.2 are independently C.sub.3 -C.sub.9 alkyl. There are numerous other pyrimidine compounds described in EP 0 332 024 A1.
It is known to incorporate pyrimidine into liquid crystal molecules. For example in Molecular Crystals and Liquid Crystals, 1971, vol. 15 pp161-74, and references therein, Demus et al describe a cyclization process for the incorporation of a pyrimidine into a target molecule. Similarly Zaschke in Journal f. prakt. Chemie, vol 317, part 4, 1975, S, 617-630 describe the synthesis of pyrimidine containing compounds via cyclization reactions. Typically an amidine ##STR4## is reacted with a diester or diacetal. This method is still used for synthesising pyrimidine containing compounds, for example see the article by Kelly and Funfschilling in J. Mater. Chem., 1993, 3(9), 953-63.
The following compounds are well known to those skilled in the field as liquid crystal compounds: ##STR5## for the above compounds the following terminology is generally used: ##STR6## are referred to as molecular cores wherein COO is a linking group and R.sub.1 and R.sub.2 are generally referred to as terminal groups. Generally a pyrimidine ring would be incorporated into the core of the molecule.
In order to incorporate a pyrimidine in to the core of a molecule then a so-called coupling reaction may be carried out. Generally the connection of two alkyl or two aryl groups is called a coupling reaction. There are both symmetrical and unsymmetrical coupling reactions. Unsymmetrical coupling reactions are also called cross-coupling reactions.
In Liquid Crystals 1993, 14, 741-61 comments on the use of ##STR7## are provided as well as details of its synthesis. This compound is also discussed in
Mol. Cryst. Liq. Cryst., 1991, 206, 187-204 and Mol. Cryst. Liq. Cryst., 1991, 204, 91-110.
There are limitations associated with the use of ##STR8##
The groups Br and Cl may be referred to as leaving groups. It is important in many chemical reactions that potential leaving groups are of different reactivity. One of the problems associated with the compound above is that the Br is more likely to act as a leaving group than is the Cl. This means that it is impossible to attach a group to the chlorine end of the pyrimidine ring first thus limiting the use of such a compound for the incorporation of a pyrimidine ring into target molecules.
It is also difficult to prepare the following compound in a pure form: ##STR9##
Typically this is prepared as follows: ##STR10##
The final compound tends to be a mixture of bromo and chloro containing compounds.
The current

REFERENCES:
The Merk Index, tenth edition, p. 692, entry 4678, 1983.
Liquid Crystals, 1993, vol. 14, No. 3, 741-761 Hird et al Palladium-catalysed cross-coupling reactions in the synthesis of some high polarizability materials.
Mol. Cryst. Liq. Cryst. 1991, vol. 206, pp. 187-204 Hird et al Cross-Coupling Reactions in the Synthesis of Liquid Crystals.
Mol. Cryst. Liq. Cryst. 1991, vol. 104, pp. 91-110 Gray et al Some Developments in the Synthesis of Liquid Crystals.

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