Nitrogen-containing tricyclic and tetracyclic compounds by stereoselective samarium diiodide promoted cyclizations of quinolyl-substituted ketones -: A new access to azasteroids

In this report, we describe our experiments dealing with samarium 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. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).