Synthesis of tribenzo[b,e,g]phosphindole oxides via radical bicyclization cascades of o-arylalkynylanilines

Jie Li, Wen-Wen Zhang, Xiao-Jing Wei, Wen-Juan Hao,* Guigen Li, Shu-Jiang Tu,* and Bo Jiang*

A new DTBP/Mg(NO₃)₂-mediated bicyclization cascade of o-arylalkynylanilines with secondary arylphosphine oxides has been developed, enabling dual C(sp²)-H functionalization along with the cleavage of the C-N bond. The combination between regioselective P-centered radical-triggered [3 + 2] cyclization and C-centered radical-induced cross-coupling in a one-pot manner delivered 27 examples of tribenzo[b,e,g]phosphindole oxides with generally high regioselectivity. A reasonable mechanism for forming such products involving radical addition-cyclization cascade is proposed.

Org. Lett. 2017, 19, 4512-4515