Palladium-Catalyzed Ullmann Cross-Coupling/Tandem Reductive Cyclization Route to Key Members of the Uleine Alkaloid Family

The trisubstituted cyclohexenone <b>12</b>, generated through a palladium-catalyzed Ullmann cross-coupling reaction between <i>o</i>-iodonitrobenzene and a 4,5-<i>trans</i>-disubstituted 2-iodo-2-cyclohexen-1-one, engaged in a tandem reductive cyclization process upon exposure to hydrogen gas in the presence of Raney cobalt. As a result, the 1,5-methanoazocino­[4,3-<i>b</i>]­indole <b>13</b> was obtained and this could be readily elaborated to the racemic modifications of the alkaloids uleine, dasycarpidone, noruleine, and nordasycarpidone (<b>1</b>–<b>4</b>, respectively)