Patent GB-602269-A (GB)
Title: Process for the preparation of hydroxy-stilbenes and related derivatives
IPC: C07C37/055
Filed: 1945-07-27
Abstract: Hydroxy stilbenes and related derivatives of the general formula <FORM:0602269/IV(b)/1> wherein R1 and R2 are phenyl radicals, one of which at least possesses one or more hydroxyl groups in the benzene ring, R2 and R4 represent hydrogen, an alkyl, alkylene, aralkyl or aryl radical such as phenyl or hydroxyphenyl and R3 and R4 may be the same or different, are prepared by reacting in the known manner an organo-magnesium, organo-zinc or organo-alkali metal compound with an aldehyde, ketone, ester, acid chloride or acid amide characterized by the feature that one or both of the reacting substances contains one or more phenolic hydroxy groups, the hydrogen of which is replaced by an alkyl group as defined below to form an ethylene derivative, and splitting off the alkyl group as defined below to restore the phenolic hydroxy group.  By alkyl group is meant any aralkyl, alkylene or cycloalkyl group or alkyl group higher than ethyl. Other substituents such as alkyl, alkoxy or halogen may be present in the benzene ring of any of the phenyl groups but p  excluding those groups such as nitro, amino or sulphonic acids groups which react with organo-metallic compounds.  Halogen derivatives of the above hydroxy-stilbenes, wherein R1, R2 and R3 have the above significance and R4 represents halogen, are prepared by reacting the intermediate ethylene derivative prepared as above with halogen or a halogenating agent in a solvent, e.g. carbon tetrachloride or acetic acid, and then dealkylating the brominated ethylene derivative as above.  The dealkylation process is effected with an acid substance such as a mixture of sulphuric or hydrobromic and acetic acids, or sulphuric acid, e.g. by heating under reduced pressure for a short while with a small quantity of 20 per cent sulphuric acid, or by means of an alkali such as potassium hydroxide in an organic solvent such as ethylene glycol or carbitol.  The hydroxy-stilbenes and their halogen derivatives prepared by the above methods may be esterified with acid halides or anhydrides of carboxylic acids, or the hydroxy-stilbenes prepared by the above method may be similarly esterified and then halogenated.  In examples: (1) a a  - di - (p - hydroxyphenyl) - b  - phenylethylene is prepared by reacting 4 : 41 - di - isopropoxybenzophenone with benzyl magnesium chloride to yield a a  - di - (p - isopropoxyphenyl)-b -phenylethylene which is dealkylated by heating with glacial acetic acid and concentrated sulphuric acid or by heating under vacuum with two drops of 20 per cent sulphuric acid; (2) a a -di-(p-hydroxy-phenyl)-b -phenylethylene is prepared by reacting 4 : 41 - di - benzyloxybenzophenone with benzyl magnesium chloride to yield di-(p-benzyloxy-phenyl)-benzyl carbinol which is first dehydrated and then dealkylated by heating with glacial acetic and concentrated sulphuric acids or by heating with glacial acetic and hydrobromic acids; (3) a a  - di - (p - acetoxyphenyl) - b  - phenylethylene is prepared by heating a a  - di - (p - hydroxyphenyl) - b  - phenylethylene, prepared as in (1) or (2), with acetic anhydride and is then brominated by heating with bromine in glacial acetic acid and acetic anhydride to yield a a  - di - (p - acetoxyphenyl)-b  - phenylbromoethylene; (4) similarly a a -di(p - propionoxyphenyl) - b  - phenylethylene is prepared using propionic anhydride; (5) a a -di-(p - hydroxyphenyl) - b  - phenylbromo-ethylene is prepared by adding bromine to a a -di-(p-isopropoxyphenyl) - b  - phenylethylene (prepared as in 1) dissolved in carbon tetrachloride to yield a a  - di - (p - isopropoxyphenyl) - b  - phenylbromoethylene, which is dealkylated by heating with glacial acetic and concentrated sulphuric acids; (6) a a - di - (p - hydroxyphenyl) - b  - phenylethylene is prepared by reacting 4 : 4'-diallyloxybenzophenone with benzyl magnesium chloride to yield a a -di-(p-allyloxyphenyl)-b -phenylethylene which is dealkylated by heating with potassium hydroxide in ethylene glycol; (7) 4-hydroxy-stilbene is prepared by reacting isopropoxybenzoldehyde and benzylmagnesium chloride and dealkylating the resulting cis or trans form of 4-isopropoxystilbene by heating with glacial acetic acid, water and concentrated sulphuric acid. Specifications 584,253 and 584,705 are referred to.