Kinetics and Mechanism of the Intramolecular Substitution of Acetate in 2′-Hydroxyphenacyl Acetate: 2′-Hydroxyphenacyl as a Potential Protective Group for Carboxylic Acids
2-Acetoxy-2′-hydroxyacetophenone (1c) undergoes cyclisation in water via its phenolate ion to release acetate and coumaran-3-one (2) at rates defined by the equation kobs = k1/[1+(10-pH)/Ka] where k1, the first order rate coefficient for the cyclisation of the phenolate ion, is 8.6 × 10−4 s−1 and Ka, the ionisation constant for 2′-OH is 2.0 × 10−9 (pKa 8.70) at 30°C.
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7.
LazarevicM., Glas. Hem. Tehnol. Makedonija1976, 3, 1. We consider that the reported product of m.p. 171 °C, identified by only elemental and IR analysis, is not 1c. It was prepared from the O-acetate of 1c using aqueous hydroxide solution in which, as shown in the present study, 1c would be unstable.
8.
Dictionary of Organic Compounds, 4th Edn, Eyre and Spottiswoode, London, 1965, Vol. 2, p. 1034.
