Preparation of Hetero‐π‐Conjugated Compounds by Double Nucleophilic Addition to Haloalkynes and C−H Cyclization

Abstract

When a mixture containing 1‐halo‐1‐alkyne, a dinucleophilic agent, and a base (Cs<sub>2</sub>CO<sub>3</sub> or K<sub>3</sub>PO<sub>4</sub>) was heated in DMF, regio‐ and stereo‐selective nucleophilic addition of the dinucleophilic agent to the acetylenes occurred. This reaction yielded (<i>Z</i>,<i>Z</i>)‐bis(haloalkene), which subsequently underwent Pd‐catalyzed cyclization through C–H bond activation, resulting in the formation of two‐oxygen‐ or ‐nitrogen‐containing hetero‐π‐conjugated compounds. <i>N</i>‐(5‐Hydroxynaphthalen‐1‐yl)methanesulfonamide was treated with 2‐phenyl‐1‐chloroethyne followed by 1‐chloro‐1‐hexadecyne. After these reactions, Pd‐catalyzed double C–H cyclization was employed to produce 1<i>H</i>‐2‐phenyl‐7‐tetradecylbenzofuro[7,6‐<i>g</i>]indole. Notably, this compound transformed into a fan‐shaped structure at 86 °C and transitioned into a smectic A phase characterized by a layered structure.