Patent GB-649028-A (GB)
Title: Improvements in or relating to beta-hydroxy-carboxylic acid lactones and process of preparing same
Filed: 1947-07-15
Abstract: Beta-lactones are obtained by reacting a ketene having the formula R1.R2.C : C : O, wherein R1 and R2 are hydrogen or aliphatic hydrocarbon groups, with a carbonyl compound having the formula R3.R4.C : O, wherein R3 and R4 are hydrogen or hydrocarbon groups free from olefinic and acetylenic bonds, in the presence of a Friedel-Crafts halide type catalyst.  Specified ketenes are ketene itself, its homologues including the aldo ketenes such as methyl (ethyl-, propyl- or butyl-) ketenes, and ketoketenes such as dimethyl (diethyl or dipropyl) ketene.  The carbonyl compound may be an aldehyde R3-CHO wherein R3 is hydrogen, an alkyl radical, an aryl radical or an aralkyl or cycloalkyl radical, or it may be a ketone R3.CO.R4, wherein R3 and R4 are alkyl, aryl, aralkyl or cycloalkyl radicals. Specified carbonyl compounds are formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, benzophenone and acetophenone.  The reaction is preferably carried out under mild conditions such as in the presence of a solvent or diluent, and at a low temperature, e.g. at below 25 DEG  C.  Specified catalysts are the halides of boron, zinc, aluminium, tin, titanium, and iron or complexes of these halides with organic compounds such as ethyl ether and ethyl chloride.  Specified solvents for the reaction are acetone, ether, methyl ethyl ether, ethyl chloride, isopropyl chloride, carbon disulphide and dioxane.  Acetone and methyl ethyl ketone may be employed as solvents for the ketene-formaldehyde reaction, since this reaction is much more rapid than that of ketene with the ketones. When acetone or methyl ethyl ketone are employed as reactants they may be added in excess quantities and thereby also serve as the solvent.  An excess of either reactant may be used, but the use of about equi-molecular proportions is preferred, especially when ketene is reacted with formaldehyde since an excess of ketene would form diketene.  Adding one of the reactants or a solution thereof to the other reactant or a solution thereof is the preferred way of conducting the reaction. In examples: (1) gaseous ketene and gaseous formaldehyde (prepared by heating a polymerized formaldehyde such as trioxymethylene or paraformaldehyde to 140-160 DEG  C.) are mixed and passed into a stirred solution of boron fluoride-ethyl ether complex in acetone at - 60 DEG  C.  A solution of sodium hydroxide in water is then added to decompose the catalyst and the reaction mixture distilled at reduced pressure to yield hydracrylic acid lactone; (2) a gaseous mixture of formaldehyde and ketene is reacted as in (1) except that the catalyst consists of zinc chloride in acetone and is maintained at 7-10 DEG  C.; (3) an ethereal solution of acetaldehyde and gaseous ketene are simultaneously added to a solution of boron fluoride-ethyl ether complex in ethyl ether at 10 DEG  to 15 DEG  C., beta-hydroxy butyric acid lactone being obtained; (4) boron fluoride ethyl ether complex is dissolved in liquid benzaldehyde and excess ketene then passed in at - 60 DEG  C.  The reaction mixture contains beta-phenyl beta-propiolactone.  When acetophenone is used instead of benzaldehyde, beta-phenyl beta - methyl beta - propiolactone is obtained.  The Specification as open to inspection under Sect. 91 is not restricted to the use of aliphatic ketenes but specifies also aromatic ketenes, e.g. phenyl ketene and diphenyl ketene.  This subject-matter does not appear in the Specification as accepted.