Patent GB-427498-A (GB)
Title: Manufacture of pyridine compounds
IPC: C07D213/50
Filed: 1933-10-26
Abstract: Quaternary salts of compounds containing a pyridine nucleus, substituted in o- or p-position to the nuclear nitrogen atom with halogen or a group by which halogen may be replaced by known methods, are condensed with aliphatic or isocyclic aromatic compounds containing a methyl, methylene or methine group which is reactive in the sense that it is capable of condensing with aldehydes or alkyl halides.  Substituents which may replace halogen in the pyridine nucleus are the hydroxy, mercapto or sulphonic groups, or an alkoxy group.  Specified compounds containing a reactive methyl, methylene or methine group are diethyl malonate, acetoacetic esters, acetophenone, acetone, and fluorene.  The reaction is effected in the presence of a basic condensing agent, such as an alkali or alkaline earth alcoholate, hydroxide or carbonate, a metal compound of the reagent undergoing condensation, or a tertiary base.  The effect of the reaction is to replace the substituent originally present in the pyridine nucleus by a residue of the second reagent, the substituent combining with a hydrogen atom from the second reagent; if the residue thus introduced into the pyridine nucleus still contains a reactive hydrogen atom, this may combine with the acid residue linked to the quaternary nitrogen atom.  In examples 1--4, condensation is effected between (a) 2-chloropyridine dimethyl sulphate and diethyl malonate; (b) 2-ethoxypyridine dimethyl sulphate and diethyl malonate; (c) 2-oxypyridine dimethyl sulphate and diethyl malonate; (d) diethyl malonate and the reaction product of 2-chloropyridine dimethyl sulphate and sodium sulphite, the same product being obtained in each case; in examples 5 and 6, condensation is effected between (a) 2-chloropyridine dimethyl sulphate and ethyl acetoacetate; (b) 2-ethoxypyridine dimethyl sulphate and ethyl acetoacetate, the same product being obtained in each case; in other examples, products are obtained from (7) 2-ethoxypyridine dimethyl sulphate and acetophenone; (8) 2-ethoxypyridine dimethyl sulphate and fluorene.  Quaternary salts prepared from methyl iodide and like halides instead of from dimethyl sulphate may also be used.  Samples have been filed under Sect. 2 (5) of products prepared from (1) N-methyl-a -pyridone dimethyl sulphate and diethyl malonate; (2) N - methyl - a  - thiopyridone dimethyl sulphate and diethyl malonate; (3) N-methyl-a -quinolone dimethyl sulphate and diethyl malonate; (4) 4-bromopyridine dimethyl sulphate and diethyl malonate.  Samples 1 and 2 are identical with the product of examples 1--4.  The Specification as open to inspection under Sect. 91 includes examples in which N-methyl-a -pyridone dimethyl sulphate is condensed (a) with a -picoline dimethyl sulphate and (b) with quinaldine dimethyl sulphate; the products of these examples are stated to be cyanine dyes useful as photographic sensitizers.  The Specification further indicates that quaternary a -and g -alkylquinolines and their derivatives and quaternary a -alkylated indoles, oxazoles, thiazoles and selenazoles may be used as second reagents, except in cases where the first reagent is a quaternary a - or g -iodopyridine or iodoquinoline derivative.  The use of a -picoline methiodide or ethiodide as the second reagent also is referred to.  This subject-matter does not appear in the Specification as accepted.