Substituents Regulate the Cyclization of Conjugated Alkynes to Accurately Construct Cyclo-( E )-[3]dendralenes.

Substituent-regulated cyclization of conjugated alkynes with acid catalysis was developed in this paper, and it provides a straightforward synthesis of cyclic-( E )-[3]dendralenes. Depending on the electronic effect of the aromatic ring pairing, a variety of phosphinyl quintuplet/hexa cyclo-[3]dendralenes with diverse substitution patterns are accessible, with good efficiency and high stereoselectivity. This self-cyclization process achieves the first precise construction of a phosphinylcyclo-( E )-[3]dendralene from conjugated alkynes to aromatization.