Disconnection at e and d bonds

In Anderson’s biogenetic-type cyclization, formation of the six membered C ring was first realized. A six membered ring system also served as a key step for free radical cyclization reported by Hee-Yoon Lee. Tandem radical cyclization was their central theme. Such radical cyclizations have been reported for the synthesis of natural products. Hee-Yoon Lee reported application of this strategy to the synthesis of α-Cedrene (Ter. Lett., 7713 (1998)). The success of this scheme hinged on two factors.

1. Selective formation of a radical for formation of ‘d’ bond to accomplish the B ring
2. The acceptor carbon should generate a new free radical in the process to complete the A ring. The first task was achieved through incorporation of a xanthane unit and the second crucial task was accomplished via., N-aziridinylimine group. The synthetic scheme is shown in Figure 1.1.

Figure 1.1