Patent GB-611072-A (GB)
Title: Improvements in or relating to a process for the manufacture of 2:5-dimethylfuran and acetonylacetone
IPC: C07D307/36
Filed: 1946-01-28
Abstract: A mercuric oxide-boron trifluoride catalyst may be used in the conversion of hex-3-en-5-yn-2-ol to 2 : 5-dimethyl furam (see Group IV (b)).  In an example, the catalyst is prepared by heating a mixture of mercuric oxide, boron trifluoride-ether complex, methyl alcohol and a few crystals of trichloro acetic acid.ALSO:2,5-Dimethyl furan is obtained by heating hex-3-en-5-yn-2-ol in the presence of a mercuric catalyst and preferably in the presence of dilute acids. Acetonylacetone may be produced by heating the 2.5-dimethyl furan with a dilute aqueous acid with or without a mercuric catalyst or may be obtained directly by prolonged heating of hex-3-en-5-yn-2-ol in a dilute aqueous acid medium, preferably in the presence of a mercuric catalyst.  The hex-3-en-5-yn-2-ol may be obtained by the isomerisation of propenylethynyl carbinol by heating the latter in the presence of a dilute acid and on continuing to heat the reaction mixture the hexenynol is converted to either 2 : 5-dimethyl furan, provided a mercuric catalyst is present, or directly to acetonylacetone. The reaction is preferably conducted at 50 to 100 DEG  C. and may be effected in an inert atmosphere, e.g. of nitrogen and in the presence of an inert organic diluent, preferably an aliphatic alcohol having not more than three carbon atoms such as methyl alcohol, or in the presence of an aqueous alcohol, e.g. aqueous ethyl alcohol.  As mercuric catalysts mercuric salts, e.g. mercuric sulphate may be used and these may be formed in situ, e.g. by the action of sulphuric acid on mercuric oxide, or a mercuric salt, e.g. mercuric chloride.  A mercuric oxide-boron trifluoride catalyst may also be used in which case the reaction is advantageously effected in the absence of water.  In examples: (1) and (2) acetonylacetone is obtained by heating hex-3-en-5-yn-2-ol, and propenylethynyl carbinol respectively with aqueous sulphuric acid and mercuric sulphate in an atmosphere of nitrogen, in (2) the mercuric sulphate is added after the mixture has first been heated and vigorously stirred; (3) steam is passed into a mixture of hex-3-en-5-yn-2-ol, mercuric sulphate and aqueous sulphuric acid until the distillate no longer separates into two layers, 2 : 5-dimethylfuran is obtained from the upper layer and may be hydrolysed to acetonyl acetone as above; (4) hex-3-en-5-yn-2-ol, mercuric chloride, water and ethyl alcohol are heated to maintain a slow rate of distillation, more mercuric chloride is added and the distillation continued until the distillate no longer separates into two layers on dilution with water.  The distillate is poured into brine and the upper layer separated and distilled to form 2 : 5-dimethylfuran; (5) a catalyst prepared by heating a mixture of mercuric oxide, boron trifluorideether complex, methyl alcohol and a few crystals of trichloracetic acid is dissolved in methyl-alcohol and a solution of hex-3-en-5-yn-2-ol in methyl alcohol added, the mixture is maintained at 50-55 DEG  C. and powdered potassium carbonate then added, 2 : 5-dimethylfuran is obtained from the decanted solution; (6) acetonylacetone is obtained by direct heating of hex-3-en-5-yn-2-ol with aqueous sulphuric acid.