Synthesis of N‐Heteroaromatic Compounds through Cyclocarbonylative Sonogashira Reactions

Abstract

A protocol based on cyclocarbonylative Sonogashira reactions has been developed for the synthesis of nitrogen‐containing heterocycles. The process is carried out under CO pressure, in the presence of a small amount of PdCl 2 (PPh 3 ) 2 (0.2–0.4 mol‐%) as a catalytic precursor, and without the need for a copper salt as cocatalyst. Suitable tosylamides reacted successfully with iodoarenes bearing electron‐withdrawing and electron‐donating groups. In particular, N ‐(2‐ethynylbenzyl)‐4‐methylbenzenesulfonamide gave carbonylmethylene isoindolines with complete chemo‐ and stereoselectivity. On the other hand, the reaction between iodoarenes and N ‐(2‐ethynylphenethyl)‐4‐methylbenzenesulfonamide did not yield tetrahydroisoquinolines as expected, but dihydrobenzoazepines were obtained.