It is well known that ester groups have a wide range of utilities. (See Kirk-Othmer Encyclopedia of Chemical Technology, 3rd. Ed. Vol. 9, John Wiley and Sons, NY, 1980, pp. 321-327.) Especially valuable are pharmaceutical esters (Ibid, "Medicinals" p. 327.) Further, a large number of acylated steroids have valuable therapeutic properties, and many possess, for example, antiinflammatory, anti-neoplastic, contraceptive or estrus regulatory properties.
There are various known processes for preparing acyl esters. More specifically, isopropenyl acetate is itself generally disclosed with acid catalysts in the preparation of acetate esters. See, for example, Hagemeyer, Jr., et al., "Reactions of Isopropenyl Acetate", Ind. Eng. Chem. Vol. 41, No. 12, pp. 2920-4 (1949) and U.S. Pat. No. 2,422,016 issued to Hull, et al. Additionally, Jeffrey, et al. reports in "Part VII The Kinetics and Mechanism of the Enol-Acetylation of Acetophenone by Isopropenyl Acetate Catalyzed by Toluene-p-sulphonic Acid." J. Chem. Soc. 1961, 1906 that the reaction is catalyzed by strong acids. This reference is cited by March, Advanced Organic Chemistry: Reactions, Mechanisms and Structure, 1968, McGraw-Hill Book Company p. 323 to generally support a disclosure of the ease with which enol esters undergo reaction with free alcohol.
A related reference is U.S. Pat. No. 2,482,066, to a method of acetylating keto-compounds and malonic acid esters using isopropenyl acetate and a catalyst which is limited to an acid or a tertiary nitrogenous material. The tertiary amines disclosed specifically in that patent do not act as catalysts in the present invention.
USPTO Backgrounds
USPTO Backgrounds