title: Synthesis of a phosphapyracene via metal-mediated cyclization: structural and reactivity effects of acenaphthene precursors.
abstract: Metal-mediated synthesis of a new heterocycle, 1-phenyl-phosphapyracene (Ph-4, Ph-PyraPhos), by tandem phosphination/cyclization of peri-substituted 5-bromo-6-chloromethylacenaphthene (3) was investigated for comparison to Pt-catalyzed formation of 1-phosphaacenaphthenes (2, AcePhos) from the analogous naphthalene precursor (1). Reaction of PH2Ph with , NaOSiMe3 and a Cu catalyst gave ; a Pt catalyst yielded PHPh(CH2Ar) (Ph-11, Ar = 5-Br-acenaphthyl). Deprotonation of a complex of this secondary phosphine, [Pt((R,R)-Me-DuPhos)(Ph)(PHPh(CH2Ar))][PF6] (17), generated the phosphido intermediate Pt((R,R)-Me-DuPhos)(Ph)(PPhCH2Ar) (Ph-8), which cyclized to give [Pt((R,R)-Me-DuPhos)(Ph)(Ph-PyraPhos)][PF6] (18). Treatment of P-8 with silver triflate gave 18 and the cyclometalated phosphine complex [Pt((R,R)-Me-DuPhos)(κ(2)-(P,C)-5-Ph2PCH2-6-C12H8)][PF6] (21), which might form via Pt(iv) intermediates. The effects of the added "ace" bridge on structure and reactivity are discussed.
authors.affiliation: 6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA. glueck@dartmouth.edu.
authors.forename: Ge
authors.initials: G
authors.lastname: Wang
authors.forename: Marites A
authors.initials: MA
authors.lastname: Guino-o
authors.forename: David S
authors.initials: DS
authors.lastname: Glueck
authors.forename: James A
authors.initials: JA
authors.lastname: Golen
authors.forename: Christopher J A
authors.initials: CJ
authors.lastname: Daley
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold