title: The Selective Cross-Coupling of Secondary Alkyl Zinc Reagents to Five-Membered-Ring Heterocycles Using Pd-PEPPSI-IHept(Cl).
abstract: The ability to cross-couple secondary alkyl centers is fraught with a number of problems, including difficult reductive elimination, which often leads to β-hydride elimination. Whereas catalysts have been reported that provide decent selectivity for the expected (non-rearranged) cross-coupled product with aryl or heteroaryl oxidative-addition partners, none have shown reliable selectivity with five-membered-ring heterocycles. In this report, a new, rationally designed catalyst, Pd-PEPPSI-IHept(Cl), is demonstrated to be effective in selective cross-coupling reactions with secondary alkyl reagents across an impressive variety of furans, thiophenes, and benzo-fused derivatives (e.g., indoles, benzofurans), in most instances producing clean products with minimal, if any, migratory insertion for the first time.
authors.affiliation: Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, M3J1P3 (Canada).
authors.forename: Bruce
authors.initials: B
authors.lastname: Atwater
authors.affiliation: Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, M3J1P3 (Canada).
authors.forename: Nalin
authors.initials: N
authors.lastname: Chandrasoma
authors.affiliation: Lilly Research Laboratories, Indianapolis, IN 46285 (USA).
authors.forename: David
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: Lilly Research Laboratories, Indianapolis, IN 46285 (USA).
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rodriguez
authors.affiliation: Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, M3J1P3 (Canada).
authors.forename: Matthew
authors.initials: M
authors.lastname: Pompeo
authors.affiliation: The Dow Chemical Company, Midland, MI 48674 (USA).
authors.forename: Robert D J
authors.initials: RD
authors.lastname: Froese
authors.affiliation: Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, M3J1P3 (Canada). organ@yorku.ca.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Organ
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D000478:Alkylation; D001555:Benzene Derivatives / Q000737:chemistry*; D002384:Catalysis; D005663:Furans / Q000737:chemistry*; D007202:Indicators and Reagents / Q000737:chemistry; D010165:Palladium / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D000473:Alkanes; D001555:Benzene Derivatives; D005663:Furans; D007202:Indicators and Reagents; D013876:Thiophenes; D010165:Palladium; D015032:Zinc
keywords: N-heterocyclic carbenes; alkyl zinc reagents; cross-coupling; palladium; transition-metal catalysis