Application of Copper(I) Iodide/Diorganoyl Dichalcogenides to the Synthesis of 4-Organochalcogen Isoquinolines by Regioselective CN and CChalcogen Bond Formation

A copper‐catalyzed cyclization of (ortho‐alkynyl)benzaldimines with diorganoyl dichalcogenides allowed the synthesis of 4‐organochalcogen isoquinolines, whereas the presence of base in the reaction medium inhibited the product formation producing the undesirable isoquinoline without the organochalcogen atom at the 4‐position. The cyclization reaction was carried out by using CuI (20 %) as a catalyst with diorganoyl dichalcogenides (1.5 equiv) in the presence of DMF at 100 °C. Furthermore, the reaction did not require an argon atmosphere and was carried out in an open flask. The cyclization reaction tolerated a variety of functional groups both in ortho‐alkynylbenzaldimines and diorganoyl dichalcogenides, such as trifluoromethyl, chloro, fluorine, and methoxyl, to give the six‐membered heterocyclic ring exclusively through a 6‐endo‐dig cyclization process. The organochalcogen group present at the 4‐position of the isoquinoline ring was further subjected to a selective chalcogen–lithium exchange reaction followed by the addition of aldehydes to afford the desired secondary alcohols in good yields. The obtained isoquinolines also proved to be suitable substrates for the Suzuki and Sonogashira coupling conditions affording the corresponding products through CC bond formation. Copper‐catalyzed cyclization of (ortho‐alkynyl)benzaldimines with diorganoyl dichalcogenides enabled the synthesis of 4‐organochalcogen isoquinolines (see scheme). The cyclization reaction tolerated a variety of functional groups both in the (ortho‐alkynyl)benzaldimines and the diorganoyl dichalcogenides, such as trifluoromethyl, chloro, fluoro and methoxyl, to give the six‐membered heterocycle through a 6‐endo‐dig cyclization process.