title: Scope and limitations of the base-catalyzed phospha-peterson P=C bond-forming reaction.
abstract: Phosphaalkenes (MesP=CRR': R = R' = Ph (1a); R = R' = 4-FC6H4 (1b); R = Ph, R' = 4-FC6H4 (1c); R = R' = 4-OMeC6H4 (1d); R = Ph, R' = 4-OMeC6H4 (1e); R = Ph, R' = 2-pyridyl (1f)) are prepared from the reaction of MesP(SiMe3)2 and O=CRR' in the presence of a trace of KOH or NaOH. The base-catalyzed phospha-Peterson reaction is quantitated by NMR spectroscopy, and isolated yields of phosphaalkene between 40 and 70% are obtained after vacuum distillation and/or recrystallization. The asymmetrically substituted phosphaalkenes (1c, 1e, 1f) form as 1:1 mixtures of E and Z isomers; however, X-ray crystallography reveals that the E isomers crystallize preferentially. Interestingly, E-1e and E-1f readily isomerize in solution in the dark, although the rate of isomerization is much faster when samples are exposed to light. X-ray crystal structures of 1b, E-1e, and E-1f reveal that the P=C bond lengths (average of 1.70 A) are in the long end of the range typically found in phosphaalkenes (1.61-1.71 A). Attempts to prepare isolable P-adamantyl phosphaalkenes following this route were unsuccessful. Although AdP=CPh2 (2a) is detected by 31P NMR spectroscopy, attempts to isolate this species afforded the 1,2-diphosphetane (AdPCPh2)2 (3a), which was characterized by X-ray crystallography.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1.
authors.forename: Mandy
authors.initials: M
authors.lastname: Yam
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Chong
authors.forename: Chi-Wing
authors.initials: CW
authors.lastname: Tsang
authors.forename: Brian O
authors.initials: BO
authors.lastname: Patrick
authors.forename: Anita E
authors.initials: AE
authors.lastname: Lam
authors.forename: Derek P
authors.initials: DP
authors.lastname: Gates