Unexpected reaction between benzaldehyde and 2,4,4,5,5-pentamethyl-1,3,2-dioxaphospholane leading to a phospha(V)oxirane dimer

Abstract

Benzaldehyde reacts with 2,4,4,5,5-pentamethyl-l,3,2-dioxaphospholane (1) to afford an oxaphosphirane (2) and its dimeric form dioxadiphosphorinane (3) in equilibrium.It is known that benzaldehyde reacts with tricovalent phosphorus derivatives leading to either a 2 : 1 adduct (Scheme 1)1,2 or a 1 : 1 adduct when it is stabilized as a zwitterionic species(I).3 With a-ethylenic ketones, ylides or phosphoranes were obtained4 (Scheme 2).We report here the reaction between benzaldehyde and 2,4,4,5,5-pentamethyl-l,3,2-dioxaphospholane (1) in dichloromethane at room temperature, resulting in a white solid after addition of hexane [m.p. 184°C (decomp.), 60%]. The remaining solution still contains a small amount of (4) and, when the solvent is not well degassed, the oxidation product of (1) (6 31P 40 p.p.m.). The elemental analyses of the new compound correspond to a 1 : 1 adduct.This compound could be oxaphosphirane (2a) or one of its zwitterionic forms (2b) (-'P+-C-Oor (2c) (:P+-0-C-.31P-{lH} n.m.r. spectra show a singlet near -25 p:p.m.,

The Quest for Ring Opening of Oxaphosphirane Complexes: A Coupled‐Cluster and Density Functional Study of CH3PO Isomers and Their Cr(CO)5 Complexes

“…In 1978, σ 4 λ 5 ‐oxaphosphiranes IV (E=NR) were first synthesized by a [2+1] cycloaddition reaction of an iminophosphine derivative and hexafluoroacetone 5. Transient σ 5 λ 5 ‐oxaphosphiranes were claimed already in 1982,6a but until 1988, when Boisdon and Barrans reported a monomer–dimer equilibrium,6b their existence was not firmly established. In 1996, a new kind of ring enlargement was proposed: a vinylcyclopropane cyclopentene‐type rearrangement of a transiently formed 3‐vinyl‐substituted oxaphosphirane; however, no strong evidence was provided for the existence of the latter 7.…”

Computational Studies on Azaphosphiridines, or How to Effect Ring‐Opening Processes through Selective Bond Activation

“…[1,2] Although some reports on related Pheterocycles (III, IV) have appeared, their "research map" still contains mostly "white spots", especially regarding structure/reactivity relationships and applications. Among these are the azaphosphiridines [3,4] III and oxaphosphiranes [5][6][7] IV, which received early attention in the late 1970s and early 1980s, concerning derivatives having four-and/or five-coordinate phosphorus centers. Reports on derivatives of III [4] with a three-coordinate phosphorus center are still scarce or even unknown, as in the case of IV.…”

“…The aforementioned weak and flexible character of the CÀN bond in 6 prompted us to study the possibility of a P V !P V isomerization at phosphorus (keeping the oxidation state the same) in a series of azaphosphiridene P-chalco-A C H T U N G T R E N N U N G genides (6)(7)(8)(9). This isomerization could take place through initial C À N bond elongation and formal insertion of the exocyclic P=Y group combined with simultaneous formation of the (exocyclic) P=NH group.…”

Protonation‐Induced Rearrangement of an Oxaphosphirane Complex

“…[1,2] Despite numerous experimental [3][4][5][6] and theoretical investigations, [7][8][9] oxiranium cations II have remained especially elusive proposed intermediates of acid-catalyzed ring-opening reactions. By comparison, protonation of s 3 l 3oxaphosphiranes [10][11][12][13][14] would presumably [15] yield P-protonated oxaphosphiranium species III, which are also unknown. In principle, kP metal coordination of a s 3 l 3 -oxaphosphirane complex should divert protonation to yield oxaphosphiranium complexes IV, and kinetic stabilization with a bulky substituent at phosphorus might allow observation of a closed-ring cation.Although oxaphosphirane complexes were first described by Mathey and co-workers almost 20 years ago, [16] and new synthetic methods, such as phosphinidene complex transfer to carbonyls [17,18] and reaction of phosphinidenoid complexes [19,20] with aldehydes, [19,21] have since been developed, the chemistry of oxaphosphiranes remains relatively undeveloped.…”

“…[1,2] Despite numerous experimental [3][4][5][6] and theoretical investigations, [7][8][9] oxiranium cations II have remained especially elusive proposed intermediates of acid-catalyzed ring-opening reactions. By comparison, protonation of s 3 l 3oxaphosphiranes [10][11][12][13][14] would presumably [15] yield P-protonated oxaphosphiranium species III, which are also unknown. In principle, kP metal coordination of a s 3 l 3 -oxaphosphirane complex should divert protonation to yield oxaphosphiranium complexes IV, and kinetic stabilization with a bulky substituent at phosphorus might allow observation of a closed-ring cation.…”