Palladium-catalyzed synthesis of 3-arylsteroids (original) (raw)

2007, Russian Journal of Organic Chemistry

Application of classical methods of organic chemistry to syntheses of aryl-and hetaryl-substituted steroids implies the necessity of using a large number of protecting groups. New synthetic approaches to arylsteroids, based on catalytic formation of CC bonds (cross coupling reactions), involve as a rule enol triflluoromethanesulfonates derived from keto steroids as initial compounds [1]. Reactions with iodosteroids are generally characterized by poor yields of arylsteroids, considerable amounts of by-products, and prolonged reaction times [2, 3]. We have recently shown that palladium-catalyzed cross coupling of 4-and 6-bromo-and-chlorosteroids with arylboronic acids provides a convenient synthetic route to arylsteroids [4, 5]. The developed procedure can be extended to 3-iodosteroids. Initial 3-iodoandrosta-3,5dien-17-ol (I) was synthesized in a moderate yield by oxidation of testosterone hydrazone with iodine [6], followed by isomerization of steroid diene mixture by the action of trifluoromethanesulfonic acid. As a result, more stable isomer I was obtained (Scheme 1).

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