Tandem Construction of Indole-Fused Phthalazines from (2-Alkynylbenzylidene)hydrazines under Metal-Free Conditions

An efficient approach to invent diversely substituted indole-fused phthalazines from in situ formed (2-alkynylbenzylidene)­hydrazines under metal-free conditions via selective radical cyclization has been developed. Notably, this 6-exo-dig addition–cyclization tandem procedure proceeds under air atmosphere and shows a broad substrate suitability, as well as avoids harmful byproducts, which complies with the concept of green synthesis.