Nitrogen‐Containing Tricyclic and Tetracyclic Compounds by Stereoselective Samarium Diiodide Promoted Cyclizations of Quinolyl‐Substituted Ketones – A New Access to Azasteroids

Abstract

AbstractIn this report, we describe our experiments dealing withsamarium diiodide promoted cyclizations of quinolyl‐substituted ketones 6–12 and also the attempted reductive cyclization of carbazole‐containing ketone 13. These precursors were prepared by Heck‐type coupling reactions of the corresponding hetaryl nonaflates with adequately substituted olefins as a key step. The cyclization of compounds 7–12 led to nitrogen‐containing tri‐ and tetracyclic compounds 23–28 in moderate to good yields and generally proceeded in a highly diastereoselective fashion. The azatetracycles present steroid‐like skeletons but with unnatural cis–cis annulation of rings B, C and D. We also describe the chemical modification of the styrene‐type double bond of these products, which provided highly functionalized steroid‐type compounds such as 29, 30 and 32.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)