Phosphetene: Synthesis and reactivity

Abstract

Four-membered ring heterocycles are less studied than five or six-membered heterocycles. It is even more true for 4-membered P-rings and in particular their unsaturated congeners, namely phosphetenes. In this review, we report the main synthetic strategies developed to prepare such compounds. The study of their reactivity, either in organic transformations or coordination chemistry, illustrates that share both specific reactivities of unsaturated strained cycles and phosphanes making them versatile synthons for original organophosphorus derivatives. Contents 1. Introduction…………………………………………………………………………………………………2 2. Synthesis of phosphetenes……………………………………………………………………………… 4 2.1. via ring expansion…………………………………………………………………………………….4 2.2. via cyclisation of phosphabutadienes………………………………………………………………7 2.3. via [2+2] cycloaddition reactions……………………………………………………………………11 2.4. via intramolecular rearrangement…………………………………………………………………..13 2.5. via addition reaction………………………………………………………………………………….14 2.6. via organometallic intermediates……………………………………………………………………14 3. Reactivity of phosphetenes……………………………………………………………………………….18 3.1. P-reactivity…………………………………………………………………………………………….19 3.2. Ring opening followed by cycloaddition……………………………………………………………20 3.3. Ring expansion…………………………………………………………………………………….…22 4. Conclusion………………………………………………………………………………………………….24

Phosphetes via Transition Metal Free Ring Closure – Taking the Proper Turn at a Thermodynamic Crossing

“…[6] Their potential revolving around their optoelectronic properties has been discovered only recently. [ 6h , 7 ] A peculiar feature of such strained heterocycles is their structural flexibility in terms of ring opening and closure which led to the description of phosphetes as masked 1‐phosphabutadienes. [6b] Somewhat related is the addition of neutral phosphane units to an adjacent alkyne leading to phosphanylidene bridged stilbenes [4e] or cyclic P‐ylidic mesoionic carbenes, [8] which attracted attention as ligand system towards transition metal centers.…”

Transition Metal-Induced Cyclization of 1-Phosphabutadienes: Selective Formation of 1-Phosphet-2-ene or P═C-Substituted Phosphacyclohexene Ligands

“…Consistent with previous reports, the palladium-mediated nucleophilic substitution of E/Z-Mes*P�C(Me)Br by 2propenylmagnesium bromide proceeds stereoselectively to exclusively produce the E-configured P�C bond. Given the interest in developing 1-phosphet-2-ene scaffolds due to their desirable ligand properties and potential applications in optoelectronic materials, 6 the scope of this novel intramolecular cyclization was investigated. Given that there are no reported Pd II complexes of 1-phosphetenes and the role of Pd II in catalytic transformations, we targeted the readily available complexes [Pd(η 3 7) and R,exo and S,exo with occupancy 0.383( 7)].…”

“…Given the interest in developing 1-phosphet-2-ene scaffolds due to their desirable ligand properties and potential applications in optoelectronic materials, the scope of this novel intramolecular cyclization was investigated. Given that there are no reported Pd II complexes of 1-phosphetenes and the role of Pd II in catalytic transformations, we targeted the readily available complexes [Pd­(η 3 -C 3 H 5 )­(μ-Cl)] 2 and [Pd­(cod)­Cl 2 ].…”

“…5 As highly strained four-membered ring systems which possess both a reactive C�C bond and an sp 3 phosphine, 1phosphet-2-enes are of considerable interest as building blocks and ligands for transition metals. 6 Since Mathey and coworkers' discovery of the first 1-phosphet-2-ene-transition metal complexes in 1985, 7 a variety of synthetic routes have been established to access these novel four-membered rings. 8 These include the aforementioned intramolecular [2 + 2] cycloaddition route (type IV).…”

Synthesis of Phosphet-2-one Derivatives via Phosphinidene Transfer to Cyclopropenones

“…12−14 Despite the growing interest in this family of molecules, the unsaturated members remain considerably underexplored due to their challenging syntheses. 2 Phosphet-2-one, the phosphorus analogue of unsaturated βlactams (azetinone), is one of the first synthetically accessible unsaturated four-membered phosphacycles (Figure 1A). Mathey et al reported the synthesis of metal complexed phosphet-2-ones by CO insertion into phosphirene complexes.…”