C-Trifluoromethyl-Substituted 1,2-Oxaphosphetane Complexes: Synthetic and Structural Study

Oxophosphonium-Alkyne Cycloaddition Reactions: Reversible Formation of 1,2-Oxaphosphetes and Six-membered Phosphorus Heterocycles

While the metathesis reaction between alkynes and carbonyl compounds is an important tool in organic synthesis, the reactivity of alkynes with isoelectronic main-group R₂E═O compounds is unexplored. Herein, we show that oxophosphonium ions, which are the isoelectronic phosphorus congeners to carbonyl compounds, undergo [2 + 2] cycloaddition reactions with different alkynes to generate 1,2-oxaphosphete ions, which were isolated and structurally characterized. The strained phosphorus-oxygen heterocycles open to the corresponding heterodiene structure at elevated temperature, which was used to generate six-membered phosphorus heterocycles via hetero Diels-Alder reactions. Insights into the influence of the substituents at the phosphorus center on the energy profile of the oxygen atom transfer reaction were obtained by quantum-chemical calculations.

Access and unprecedented reaction pathways of Li/Cl phosphinidenoid iron(0) complexes

Complexes [Fe(CO)₄(RPCl₂)] (2) (a: R = CPh₃, b: R = ^tBu) were used to generate the first examples of phosphinidenoid iron(0) complexes [Li(12-crown-4)(solv)_n][Fe(CO)₄(RPCl] (3a,b), characterized by NMR spectroscopy.

Addressing the Nature of Phosphinidene Sulfides via the Synthesis of P-S Heterocycles

The phosphorus-sulfur heterocycles 1,2-thiaphosphetenes and phosphirene sulfides have been prepared, and represent the first structurally characterized derivatives for either class of compound. These strained P-S ring systems are formed by the reaction of a phosphinidene sulfide and alkyne. Using an internal alkyne, only the 3-membered P^V , phosphirene sulfide was produced, whereas a terminal alkyne yielded a mixture of phosphirene sulfide and 1,2-thiaphosphetene (P^III ). Detailed computational analysis revealed that for numerous derivatives of alkynes, the corresponding 4-membered rings are always more stable than the 3-membered isomers. The electronic nature of "free" phosphinidene sulfides (R-P=S) is discussed based on computational results.

Ring opening of a sterically crowded 1,2-oxaphosphetane complex

The first example of a ring opening reaction of a 1,2-oxaphosphetane complex is reported, i.e., water in the presence of [Li(12-crown-4)]Cl furnished a C–OH functional phosphinito complex. Employment of the latter in ring forming reactions with Me₂ECl₂ (E = Si, Ge) using different nitrogen bases is also described.

A novel route to C-unsubstituted 1,2-oxaphosphetane and 1,2-oxaphospholane complexes

The synthesis of 1,2-oxaphosphetane complexes 7 and 1,2-oxaphospholane complex 12 bearing only substituents at phosphorus is reported using the reaction of Li/Cl phosphinidenoid complex 2 with 2-iodoethanol or 3-bromo-propane-1-ol and the subsequent dehydrohalogenation using KHMDS.