Triphenylphosphaalkenes in Chemical Equilibria

Abstract

Triphenylphosphaalkenes 1a-c were prepared in good to excellent yields in a modified phospha-Peterson reaction between PhP(Li)TMS and benzophenones with different para-substituents at the C-phenyl groups (a: R = H, b: R = Ooctyl, c: R = F). Owing to the low kinetic stabilization that is provided by the P-phenyl group, compounds 1a-c engage in [a]

Isolable Phosphaalkenes Bearing 2,4,6-Trimethoxyphenyl and 2,6-Bis(trifluoromethyl)phenyl as P-Substituents

“…31 P NMR (162 MHz, CDCl 3 , δ): 156.5 (s); 1 H NMR (400 MHz, CDCl 3 , δ): 6.10 (s, 1H), 6.09 (s, 1H), 3.87 (s, 6H), 3.84 (s); 13 Synthesis of TMOP−P(SiMe 3 ) 2 (4a). Primary phosphine 3a (0.89 g, 4.46 mmol) was dissolved in THF (80 mL) and cooled to −78 °C.…”

“…Yield: 0.51 g (33%). 31 P NMR (121 MHz, CDCl 3 , δ): −179.4 (s); 1 H NMR (300 MHz, CDCl 3 , δ): 6.12 (s, 2H), 3.82 (s, 3H), 3.78 (s, 6H), 0.20 (s, 9H), 0.18 (s, 9H); 13 O (50 mL) and the mixture was stirred at room temperature for 24 h. An aliquot of the reaction mixture was taken and checked by 31 P NMR spectroscopy to confirm the formation of 3b′ (δ P = −134). Upon reaction completion, the lower layer (containing NEt 3 HOTf) was separated and removed.…”

“…We became intrigued by the isolable phosphaalkene E which appeared to lie at the interface of kinetic/thermodynamic stability given that o -Tol−PCPh 2 was not isolable as a monomer and reportedly gave only an ill-defined “polymeric material” . We later showed that o -Tol−PCPh 2 and Ph−PCPh 2 afford monomer–dimer equilibria in solution and Ott and coworkers have postulated that such equilibria may also consist of higher oligomers and/or polymers …”

“…8 We later showed that o-Tol−PCPh 2 and Ph−PCPh 2 afford monomer−dimer equilibria in solution 12 and Ott and coworkers have postulated that such equilibria may also consist of higher oligomers and/or polymers. 13 Monomer E and related P-Mes monomers may be polymerized to afford functional phosphine-containing polymers, poly(methylenephosphine)s, which have attractive chemical and physical properties. 2d,14,15 Of particular interest to us has been the mechanism of polymerization.…”

Metathesis of P=C Bonds Catalyzed by N‐Heterocyclic Carbenes

“…Remarkably, the aforementioned results suggest that Me 2 IMe can induce the unprecedented cleavage of a P=C bond. Although 1 Mes showed no reaction with more sterically hindered Me 2 I i Pr even after gentle heating (Figure 1c), both 1 o-Tol and 1 Ph [20,21] react cleanly with Me 2 IMe and Me 2 I i Pr. [16] In contrast to monomeric 1 Mes , THF solutions of 1 Ph and 1 o-Tol exist in equilibrium with their respective 1,2-dimers, , 1f, 1h, 1i).…”