The [4+2] cycloaddition reaction between 2-pyrone and Me Si-C≡P gives the corresponding 2-(trimethylsilyl)-λ -phosphinine in good yields as a rather air and moisture stable, colorless oil. Insight into the regioselectivity of the pericyclic reaction was obtained with the help of deuterium-labeling experiments. The silyl-phosphinine acts as a ligand for the preparation of a Cu(I) and the first crystallographically characterized phosphinine-Ag(I) complex. The title compound was further used as a starting material for an alternative preparation of the parent phosphinine C H P by means of protodesilylation with HCl. C H P reacts with CuBr⋅S(CH ) to give an infinite Cu(I)Br coordination polymer. DFT calculations shed light on the influence of the -Si(CH ) group on the electronic properties of the aromatic phosphorus heterocycle.

The synthesis and isolation of a phosphinine selenide was achieved for the first time by reacting red selenium with 2,6-bis(trimethylsilyl)phosphinine. The rather large coupling constant of 1 J P,Se = 883 Hz is in line with a PÀ Se bond of high s-character. The σ-electron donating Me 3 Sisubstituents significantly increase the energy of the phosphorus lone pair and hence its basicity, making the heterocycle considerably more basic and nucleophilic than the unsubstituted phosphinine C 5 H 5 P, as confirmed by the calculated gas phase basicities. NBO calculations further reveal that the lone pairs of the selenium atom are stabilized through donor-acceptor interactions with antibonding orbitals of the aromatic ring. The novel phosphinine selenide shows a distinct reactivity towards hexafluoro-2-butyne, Au(I) Cl as well as i PrOH. Our results pave the way for new perspectives in the chemistry of phosphorus in low coordination.

The facile access to 3-bromo-2-pyrone allows the preparation of 6-bromo-2-trimethylsilyl-phosphinine by a [4+2] cycloaddition with Me3 Si-C≡P for the first time. The regioselectivity of this reaction could be verified by means of single crystal X-ray diffraction of the corresponding W(0) complex. In the presence of ZnBr2 and dppp (1,3-bis(diphenylphosphino)propane) as a bidentate ligand, the bromo-phosphinine quantitatively undergoes a Negishi cross-coupling reaction with PhLi that selectively leads to 6-phenyl-2-trimethylsilyl-phosphinine. This heterocycle could again be characterized by means of X-ray diffraction as a W(0) complex. These results describe a new and convenient route to 2,6-disubstituted phosphinines that makes use of readily available starting materials.

For the first time the direct synthesis of 1-methyl-phosphininium salts has been achieved by reacting aromatic λ3,σ2-phosphinines with the readily available dimethyl chloronium salt [(CH3)2Cl]+[Al(OTeF5)4]-. The remarkably high electrophilicity of...

The palladium-catalyzed directed C-H halogenation of bipyridine N-oxides was investigated. Using NCS or NBS (N-chloro- or N-bromosuccinimide) and 5 mol % Pd(OAc) in chlorobenzene (0.10 molar) at 110 °C, pyridine-directed functionalization took place and 3-chloro- or 3-bromobipyridine N-oxides were obtained in high yields. The reaction is sensitive to steric hindrance by 4- and 6'-substituents. Only in the latter case, where coordination of palladium by the pyridine is hindered, 3'-halogenation directed by the N-oxide function was observed. The halogenated products were deoxygenated by PCl or PBr.