Steroids, .45. Neighboring Group Participation .12. Decomposition Of (Z)-16-Amidomethylene-17-Beta-Hydroxysteroids Mediated By Neighboring Group Participation

The sodium tetrahydroborate reduction of 16-[[acetyl(alkyl)amino]methylene]-17-ketosteroids 1aa, 2aa and 2ba affords (Z)-16- and (E)-16-[[acetyl(alkyl)amino]methylene]-17-beta-hydroxysteroids (Z)-3, (E)-3, (Z)-4b, (Z)-4a, (Z)-5c and (E)-5a. The N-acetyl group of the (Z) isomers (Z)-3, (Z)-4b, and (Z)-5c migrates to the 17-beta-hydroxyl in inert solvents, and the products suffer secondary transformation into unsaturated aldehydes 6 and 9a; intermediate 8 has been isolated. The (E) isomers (E)-3, and (E)-5a do not change, even not under more drastic conditions.