Journal of Organic Chemistry p. 2816 - 2821 (1980)
Update date:2022-08-10
Topics:
Perera, S. K.
Dunn, W. A.
Fedor, L. R.
Isomerization of androst-5-ene-3,17-dione (1) to androst-4-ene-3,17-dione (2) and of 17α-ethynyl-17β-hydroxy-5-estren-3-one (3) to 17α-ethynyl-17β-hydroxy-4-estren-3-one (4) is kinetically general acid-base catalyzed; 1 is more reactive than 3.Deuterium solvent kinetic isotope effects, k(H2O)/k(D2O), of ca.6 for tertiary amine catalyzed isomerization indicate rate-determining protonation of dienolate ions.The greater reactivity of 1 than 3, catalyzed by tertiary amines, is probably due to a greater concentration of the 1 dienolate ion than of the 3 dienolate ion.Ethanolamine, but not tris(hydroxymethyl)aminomethane, catalyzes isomerization of 1 and 3 via Schiff-base formation.Curvilinear pseudo-first-order plots for isomerization of 1 and 3 catalyzed by DCl/D2O indicate that partitioning of dienols is kinetically important.
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