Stereo‐ and Regiospecific 6‐ endo ‐ trig ‐Cyclization of Aryl Radicals, an Entry to Novel Progesterone‐Antagonists of the Androstane Series

The phenyl radicals 1 undergo 6‐ endo‐trig cyclization instead of the 5‐ exo‐trig cyclization observed for simple alkenylphenyl radicals. The cyclization products 2 are key compounds for the synthesis of 3 (e.g., XOH, YCCCH 3 ), the first competitive progesterone antagonists in the androstane series. The formation of 2 by a neophyl rearrangement can be excluded for steric reasons. RH, OCH 3 , N(CH 3 )2.