Synthesis of Polycyclic Fused Indoline Scaffolds through a Substrate-Guided Reactivity Switch

Zn­(II)-catalyzed
divergent synthesis of functionalized polycyclic
indolines through formal [3 + 2] and [4 + 2] cycloadditions of indoles
with 1,2-diaza-1,3-dienes (DDs) is reported. The nature and type of
substituents of substrates are found to act as a chemical switch to
trigger two distinct reaction pathways and to obtain two different
types of products upon the influence of the same catalyst. The mechanism
of both [4 + 2] and [3 + 2] cycloadditions was investigated and fully
rationalized by density functional theory (DFT) calculations.