Au(i)-mediated N2-elimination from triazaphospholes: a one-pot synthesis of novel N2P2-heterocycles

Novel tosyl- and mesitylsulfonyl-substituted triazaphospholes were synthesized and structurally characterized. In an attempt to prepare the corresponding Au(I)-complexes with stoichiometric amounts of AuCl·S(CH3)2, cyclo-1,3-diphospha(III)-2,4-diazane-AuCl-complexes were obtained instead. Our here presented results offer a new strategy for preparing such coordination compounds selectively in a one-pot approach

Phospholenes from Phosphabenzenes by Selective Ring Contraction

A 3-aminofunctionalized phosphabenzene (phosphinine) was synthesized and structurally characterized. The pyramidalized nitrogen atom of the dimethylamino substituent indicates only a weak interaction between the lone pair of the nitrogen atom and the aromatic phosphorus heterocycle, resulting in somewhat basic character. It turned out that the amino group can indeed be protonated by HCl. In contrast to pyridines, however, the phosphabenzene-ammonium salt undergoes a selective ring contraction to form a hydroxylphospholene oxide in the presence of additional water. Based on deuterium labelling experiments and quantum chemical calculations, a rational mechanism for this hitherto unknown conversion is proposed

Triple dehydrofluorination as a route to amidine-functionalized, aromatic phosphorus heterocycles

An unexpected route to hitherto unknown amidine-functionalized phosphinines has been developed that is rapid and simple. Starting from primary amines and CF3-substituted λ3,σ2-phosphinines, a cascade of dehydrofluorination reactions leads selectively to ortho-amidinephosphinines. DFT calculations reveal that this unusual transformation can take place via a series of nucleophilic attacks at the electrophilic, low-coordinate phosphorus atom

Phospholenes from Phosphabenzenes by Selective Ring Contraction

A 3-amino-functionalized phosphabenzene (phosphinine) has been synthesized and structurally characterized. The pyramidalized nitrogen atom of the dimethylamino substituent indicates only a weak interaction between the lone pair of the nitrogen atom and the aromatic phosphorus heterocycle, resulting in somewhat basic character. It turned out that the amino group can indeed be protonated by HCl. In contrast to pyridines, however, the phosphabenzene-ammonium salt undergoes a selective ring contraction to form a hydroxylphospholene oxide in the presence of additional water. Based on deuterium labeling experiments and quantum chemical calculations, a rational mechanism for this hitherto unknown conversion is proposed

Triple dehydrofluorination as a route to amidine-functionalized, aromatic phosphorus heterocycles

Hitherto unknown amidine-functionalized phosphabenzenes selectively form by a cascade of dehydrofluorination reactions

Phosphorus derivatives of mesoionic carbenes: synthesis and characterization of triazaphosphole-5-ylidene → BF3 adducts

Trimethylsilyl-substituted triazaphospholes were synthesized by a [3+2] cycloaddition reaction between organic azides and (CH3)3Si–C[triple bond, length as m-dash]P. In an attempt to isolate their N-alkylated products, the formation of BF3 adducts of unprecedented triazaphosphol-5-ylidenes was found. The nature of the carboncarbene–boron bond was investigated within the DFT framework, revealing a strong donation of electrons from the carbene carbon atom to the boron atom combined with weak back-bonding

A new access to diazaphospholes via cycloaddition–cycloreversion reactions on triazaphospholes

A novel bis-CF3-substituted diazaphosphole was synthesized selectively from hexafluoro-2-butyne and a 3H-1,2,3,4-triazaphosphole derivative. The [4+2] cycloaddition and subsequent cycloreversion reaction under elimination of pivaloyl nitrile affords the product in high yield. The heterocycle coordinates via the phosphorus atom to a W(CO)5-fragment and shows stronger π-accepting properties than the triazaphosphole

Highly flexible phosphabenzenes: a missing coordination mode of 2,4,6-triaryl-λ3-phosphinines

The reaction of 2,4,6-triaryl-λ3-phosphinine-Cr(CO)3-π-complexes with [Rh(COD)2]BF4 leads to unusual diamagnetic Rh0-dimers, which contain two phosphinine-π-complexes acting as a bridging 2e−-ligand towards the Rh2(CO)2 core. These compounds represent a missing coordination mode for the aromatic 6-membered phosphorus heterocycle