title: Biphenyl-derived phosphepines as chiral nucleophilic catalysts: enantioselective [4+1] annulations to form functionalized cyclopentenes.
abstract: Because of the frequent occurrence of cyclopentane subunits in bioactive compounds, the development of efficient catalytic asymmetric methods for their synthesis is an important objective. Introduced herein is a new family of chiral nucleophilic catalysts, biphenyl-derived phosphepines, and we apply them to an enantioselective variant of a useful [4+1] annulation. A range of one-carbon coupling partners can be employed, thereby generating cyclopentenes which bear a fully substituted stereocenter [either all-carbon or heteroatom-substituted (sulfur and phosphorus)]. Stereocenters at the other four positions of the cyclopentane ring can also be introduced with good stereoselectivity. An initial mechanistic study indicates that phosphine addition to the electrophilic four-carbon coupling partner is not the turnover-limiting step of the catalytic cycle.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 (USA).
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Ziegler
authors.forename: Lorena
authors.initials: L
authors.lastname: Riesgo
authors.forename: Takuya
authors.initials: T
authors.lastname: Ikeda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Fu
mesh_terms: D002384:Catalysis; D003500:Cyclization; D003517:Cyclopentanes / Q000737:chemistry*; D008958:Models, Molecular; D010720:Phosphines / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D003517:Cyclopentanes; D010720:Phosphines
keywords: annulation; asymmetric catalysis; atropisomerism; organocatalysis; phosphane