Pd- and Ni-Catalyzed Cross-Coupling Reactions of Functionalized Organozinc Reagents with Unsaturated Thioethers

A variety of unsaturated thioethers have been subjected to cross-coupling reactions with functionalized zinc reagents in the presence of a transition-metal catalyst. Three different catalytic systems based on Pd(OAc)(2) or [Ni(acac)(2)] and the ligands S-Phos or DPE-Phos gave the best results. N-Heterocyclic thioethers based on a pyridine, pyrimidine, pyrazine, pyridazine, triazine, benzothiazole, benzoxazole, pyrrole, or quinazoline ring, as well as thiomethylacetylenes, serve as electrophiles in this cross-coupling reaction. Aryl-, heteroaryl-, benzylic, and alkyl-zinc halides with sensitive functionalities, such as ester, nitrile, or ketone groups react at ambient temperature with unsaturated thioethers using a Ni catalyst. The corresponding Pd-catalyzed reactions require slightly higher temperatures. Large-scale cross-coupling experiments (10-20 mmol) with N-heterocycles are also reported.