Radical cyclisations to arenes for the synthesis of phenanthrenes

Total Syntheses of Telisatin A, Telisatin B and Lettowianthine

“…The antiplatelet activity of such 1-aryl-5,6-dihydropyrrolo[2,1-a]-isoquinoline-2,3-dione derivatives has been reported [ 9 ]. To overcome the limitations of photochemical cyclisation under extreme dilution and based on previous reports on the radical cyclisation of halostilbenes to phenanthrenes [ 10 , 11 , 12 , 13 , 14 ], solutions (0.025 M) of 1-(2-bromophenyl)-5,6-dihydropyrrolo[2,1-a]isoquinoline-2,3-dione derivatives 10a - 10c were treated with tributyltin hydride in the presence of 1,1ʹ-azobis(cyclohexanecarbonitrile) (ACCN) to give the corresponding telisatin-type alkaloids in 30-34% yields.…”

Total Synthesis of Cavicularin and Riccardin C: Addressing the Synthesis of an Arene That Adopts a Boat Configuration

“…In planning the synthesis of cavicularin, we identified two problems that required special consideration: one was the obvious kinetic barrier to closure of the strained macrocycle; the other was a thermodynamic constraint imposed by the need to distort arene A. We felt that both of these problems could be resolved by employing a radical‐induced, transannular ring‐contraction strategy, such as 2 → 3 (Scheme ) 2. In particular, by employing a larger and less‐strained macrocycle as a precursor the kinetic burden would be transferred to the ring‐contraction step, in which the close proximity of the aryl radical intermediate to arene D offered good prospects for a favorable outcome.…”

(Bu3Sn)2–TBAF: a new combination reagent for the reduction and deuteration of aryl bromides and iodides

“…The examples indicated in Table 1 are testament to the effectiveness of the new procedure. 8 With a free radical mechanism negated, we concluded that the likely course of the reduction was halogen to metal exchange followed by protonation. 7 At this juncture we decided to probe the mechanistic course of the reaction.…”