Patent GB-699042-A (GB)
Title: 4-nitro--a-methoxy styrene and a process for the preparation of -a-halo-p-nitroacetophenone
Filed: 1951-07-03
Abstract: The invention comprises 4-nitro-a -methoxystyrene, and a process for preparing a -bromo- or a  - chloro - p - nitroacetophenone by reacting styrene with methanol and chlorine in the proportion of 2.18 to 2.28 atoms of chlorine per mol. of styrene, at a temperature of -5 DEG  to 5 DEG  C., e.g. in the presence of an acid binding agent, nitrating the reaction product with a mixed acid consisting of approximately 30 per cent nitric acid, 60 per cent sulphuric acid and 10 per cent water by weight, at a temperature ranging from -5 DEG  to 5 DEG  C., dehydrohalogenating the mixture of mononitro isomers by heating in the presence of alcoholic sodium or potassium hydroxide, separating the 4-nitro-a -methoxy styrene by cooling and filtering after the sodium or potassium chloride is filtered off from the hot solution, and hydrolysing it to p-nitroacetophenone by heating with acetic acid containing water with or without a small amount of another acid, e.g. hydrochloric, sulphuric, phosphoric, hydrobromic, p-toluenesulphonic or trichloroacetic acid, and halogenating the hydrolysed product with bromine or chlorine.  The a -bromo- or a -chloro-p-nitroacetophenone may be prepared by nitrating a -(chloromethyl)-benzylmethyl ether to the mononitro isomers thereof with a mixed acid consisting of approximately 30 per cent nitric acid, 60 per cent sulphuric acid and 10 per cent water by weight at a temperature ranging from -5 DEG  to 5 DEG  C. and then following the subsequent reactions as above.  When a -bromo-p-nitroacetophenone is prepared, the nitration step may be carried out at a temperature ranging from 0 DEG  to -3 DEG  C., and the dehydrochlorination step may be carried out with methanol-sodium hydroxide solution.  The initial treatment of styrene with methanol and chlorine forms a mixture of a -(chloromethyl)-benzylmethyl ether and styrene dichloride which mixture on nitration gives a  - (chloromethyl) - p - nitrobenzylmethyl ether as well as the o- and m-isomers and nitration products of styrene dichloride, and on dehydrohalogenating the desired 4-nitro-a -methoxy styrene is formed together with the o- and m-isomers, the nitration products of styrene dichloride being also present.  One example is given. The Specification refers briefly to a number of prior art methods for the preparation of p-nitroacetophenone as follows: (a) the acylation of the sodium or the magnesium methoxy or ethoxy derivative of diethylmalonate with p-nitrobenzoyl chloride and the acyl derivative is then hydrolysed and decarboxylated; (b) the hydration of p-nitrophenyl propiolic acid followed by decarboxylation; (c) the condensation of p-nitrobenzoyl chloride with acetoacetic ester followed by hydrolysis and decarboxylation; (d) the air oxidation of p - nitro - ethylbenzene in the presence of chromium oxide; (e) the nitration and subsequent oxidation of methylphenyl carbinol; (f) the treatment of p-nitro-ethylbenzene with t.-butylnitrite and sodium t.-butoxide followed by hydrolysis of the resulting oxime; and (g) the nitration of a  - (chloromethyl)-benzylmethyl ether followed by dehydrohalogenation and hydrolysis.