title: Three-step synthesis of an annulated β-carboline via palladium catalysis.
abstract: The synthesis of β-carbolines is a mature field, yet new methods are desirable to introduce new functionality onto the core scaffold. We describe the incorporation of an additional fused ring onto the β-carboline via a novel palladium-catalyzed, one-pot Sonogashira coupling/intramolecular [2+2+2] cyclization. This method generates three rings in one flask and produces an annulated β-carboline in 80% yield. A preliminary mechanistic study into the sequence of events is described, which confirms an unprecedented catalytic role for palladium.
authors.affiliation: Providence College, Department of Chemistry and Biochemistry, 1 Cunningham Square, Providence, RI 02908, USA.
authors.forename: Seann P
authors.initials: SP
authors.lastname: Mulcahy
authors.affiliation: Providence College, Department of Chemistry and Biochemistry, 1 Cunningham Square, Providence, RI 02908, USA.
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Varelas
keywords: Sonogashira coupling; cyclotrimerization; heteroannulation; palladium catalysis; β-carboline