Mixed Phosphonium Iodonium Ylide Research Articles

Phenoxaphosphonium Mixed Ylides in Ring Expansion Reaction.

Treatment of mixed phosphonium-iodonium ylides featuring a six-membered phenoxaphosphonium fragment with aqueous tetrafluoroboronic acid induces a rearrangement, resulting in expansion of the phosphacycle and oxidation of the phosphorus atom. The target difficult-to-access dibenzo[b,f][1,4]oxaphosphepine oxides (3 examples) were isolated in excellent yields (up to 95%) as mixtures of stereoisomers. Hydrolysis of a five-membered mixed ylide, a dibenzophosphole derivative, predominantly preserves the phosphole system with cycle expansion occurring as a side process.

Regioselective heterocyclization of mixed phosphonium-iodonium ylides with acetylenes involving dimethyl acetylenedicarboxylate

Regioselective heterocyclization of mixed phosphonium-iodonium ylides with acetylenes involving dimethyl acetylenedicarboxylate

A new P-heterocyclic type of phosphonium–iodonium ylides based on dibenzophosphole

A novel mixed phosphonium–iodonium ylide was synthesized by alkylation of 5-phenyl-5H-dibenzophosphole with phenacyl bromide followed by deprotonation and oxidation of the resulting phosphonium ylide with (diacetoxyiodo)- benzene. The influence of the cyclic nature of the phosphonium moiety on the dynamic E/Z isomerism in the mixed ylide is discussed.

A novel structural type of conformationally fixed, mixed phosphonium-iodonium ylides based on phenoxaphosphinine

A synthetic approach to a novel type of phosphonium and mixed phosphonium-iodonium ylides containing a conformationally fixed phosphonium fragment is developed. New representatives of these families of chemical compounds based on cyclic phenoxaphosphinine were synthesized. One compound was structurally characterized by single-crystal X-ray diffraction. Based on the 1H NMR data, one can state that phosphonium ylide exists in solution in the form of two geometric isomers even at room temperature. This is indicative of pronounced double-bond character of the bond between the ylide carbon atom and the stabilizing carbomethoxy group.

Photosensitization of the Reaction of Mixed Phosphonium–Iodonium Ylide with 9-Ethynylphenanthrene

Photosensitization of the Reaction of Mixed Phosphonium–Iodonium Ylide with 9-Ethynylphenanthrene

Remarkable Mechanism of the Reaction between Mixed Phosphonium-Iodonium Ylides and Acetylenes

Reactions of mixed phosphonium-iodonium ylides with nitriles and acetylenes allow for the synthesis of not easily accessible and novel heterocyclic compounds in a simple, one-pot, metal-free system. The results of the mechanistic investigation of the reaction of the phosphonium-iodonium ylides with acetylenes by means of spectrophotometry, EPR and NMR spectroscopy are discussed in this review. This investigation allows to account for unusual regularities of these reactions: induction time, acid catalysis, chemically induced dynamic nuclear polarization effect (CIDNP) observed in several systems, and others. The radical character of the initiation of the reaction as a result of acid catalysis of the ylides decomposition on radicals and the participation of radical intermediates in the formation of all target products have been unambiguously established. The mechanism of generation of radical pairs in CIDNP was suggested, and the role of microheterogeniety of the ylide solutions in methylene chloride was substantiated. On the basis of the study of the reaction mechanism, the conditions for the increase in the yields of new heterocyclic compounds can be optimized.

Radical Intermediates in Reactions of Mixed Phosphonium–Iodonium Ylides

The active intermediates generated in the photolysis of phosphonium–iodonium ylides and their reaction with acetylenes have been studied with electron and nuclear magnetic resonance spectroscopy. The radical mechanism of the ylides decomposition and of the interaction with acetylenes has been established using a stable nitroxyl radical. The radical products of these reactions have been monitored for the first time by EPR, and their spectroscopic parameters were determined. The chemical structure of the active intermediates of the reactions under study has been proposed.

CIDNP as a tool to unveil the reaction mechanism: interaction of mixed phosphonium-iodonium ylide with p-methoxyphenylacetylene.

In situ acquisition of the reaction between benzoyl phosphonium–iodonium ylide and p-methoxyphenylacetylene in an NMR spectrometer reveals the CIDNP effect in 31P and 1H NMR spectra of major products, substituted furan (emission) and phosphonium salt (enhanced absorption). The mechanism of products formation via radical pairs is discussed.

The Role of an Acid in the Decomposition of Mixed Benzoyl-Substituted Phosphonium–Iodonium Ylide

Abstract—Mixed phosphonium–iodonium ylides allow the synthesis of not easily accessible and novel heterocyclic compounds. Photoinitiated reactions of phosphonium–iodonium ylides with acetylenes proceed with induction time and are catalyzed by acids, the acids formed in the reaction among them. The kinetic peculiarities of the reaction between the benzoyl-substituted phosphonium–iodonium ylide and trifluoroacetic acid were studied by UV-visible spectrophotometry. The kinetic parameters of the reaction were determined. The mechanism of the autocatalysis by acids has been proposed, which involves the formation of a protonated form of the ylide active in the decomposition into radical cations. The more active decomposition of the protonated ylide is confirmed by theoretical thermochemical calculations.

Free radicals in photolysis of mixed phosphonium–iodonium ylides and in their reactions with acetylenes

UV irradiation of mixed phosphonium–iodonium ylide in CH2Cl2 leads to formation of free radicals with lifetimes of a few minutes detected by EPR. In mixtures of ylides with acetylenes, the structure of radicals changes, and their concentration and stability increase. In the presence of acetylenes, the radicals contain ylide and acetylene residues, and their EPR spectra have hyperfine coupling constants typical for 31P nuclei in C-radicals and for 1H nuclei, depending on the acetylene structure. It has been demonstrated that the observed radical products are formed from short-lived primary radicals.

Furyl‐Substituted Mixed Phosphonium–Iodonium Ylides in the Synthesis of Annelated P‐Containing Heterocyclic Compounds

AbstractPhotochemical reactions between stabilized furyl‐substituted phosphonium–iodonium ylides and terminal acetylenes led to the formation of new P‐containing heterocyclic compounds. For the heterocyclization of 2‐furyl‐substituted ylides, we observed an unprecedented electrophilic ipso attack onto the α position of the furan ring in a carbocationic intermediate, leading – via a spiro intermediate – to the rearranged product with a 2,3‐shift in the furan ring.

Photocyclization of a mixed phosphonium-iodonium ylide with phenylacetylene: A formal kinetic approach to the mechanistic study

The recently discovered photoheterocyclization of a mixture of mixed phosphonium-iodonium ylides and acetylene compounds to give λ5-phosphinoline, a new phosphorus-containing heterocycle, occurs with self-acceleration and an induction period at relatively high concentrations of the reactants. The reaction was found to be catalyzed by the acid formed during photolysis. We developed a spectrophotometric method to study the kinetics of photocyclization between phenylacetylene and a phosphonium-iodonium ylide in the presence of trifluoroacetic acid and studied how the yield of target λ5-phosphinoline and kinetic parameters of the reaction, such as the induction period and maximum rate of product formation, depend on the initial concentrations of the starting compounds and catalyst. It was shown that the addition of the acid has no effect on the critical character of the dependence of the reaction on the concentration of the starting compound: the reaction proceeds only at an ylide concentration of >0.02 mol/L in a microheterogeneous suspension and the self-accelerating character of λ5-phosphinoline formation is preserved. The optimum reagent ratios maximizing the yield of the target product were determined. The acid was found to play a dual role: it catalyzes the reaction only at concentrations not higher than the initial ylide concentration. At higher acid concentrations, no formation of λ5-phosphinoline was observed.

Mechanism and remarkable features of photoinduced cycloaddition of phenylacetylene to mixed phosphonium-iodonium ylide

Mechanism and remarkable features of photoinduced cycloaddition of phenylacetylene to mixed phosphonium-iodonium ylide

Hetaryl-Substituted Phosphonium-Iodonium Ylides in Synthesis of Heterocycles

A series of hitherto unknown hetaryl-substituted (in phosphonium part) phosphonium-iodonium ylides were synthesized. The reaction of these mixed phosphonium-iodonium ylides with acetylenes opens a way to new furyl annelated phosphinolines or unusually substituted phosphininofurans.

On the mechanism of photoinduced addition of acetonitrile to phosphonium–iodonium ylides

Recently, a novel photochemical reaction of pseudocycloaddition of nitriles to mixed phosphonium–iodonium ylides 1 was found. Nitriles R1CN give corresponding oxazoles (2) with a high yield, with PhI (3) being a leaving group. The mechanism of the photoinduced cycloaddition of acetonitrile to mixed phosphonium–iodonium ylide 1 was studied by steady‐state and time‐resolved methods with resolution from 10 ns to 20 µs. The formation of photolysis products, substituted oxazole 2, and phosphonium salt 4, occurs in parallel reactions. The primary photochemical processes for the formation of 2 and 4 are the heterolytic and homolytic C–I+Ph bond cleavage in the excited singlet state of 1, respectively. Three transient species with lifetimes on microsecond and millisecond time scales were observed. The mechanism of the formation of major and minor products of the photolysis was suggested. Addition of water to the reaction mixture in acetonitrile changes the ratio of the products in favor of the phosphonium salt formation. The effect of water was accounted for by the acid catalysis of the homolytic C–I+Ph bond cleavage and the acceleration of the salt formation. Copyright © 2012 John Wiley & Sons, Ltd.

ChemInform Abstract: A Novel Photochemical Reaction of a Mixed Phosphonium Iodonium Ylide with Phenylacetylene as a Route to Diphenyl‐1λ5‐phosphinoline.(III).

ChemInform Abstract: A Novel Photochemical Reaction of a Mixed Phosphonium Iodonium Ylide with Phenylacetylene as a Route to Diphenyl‐1λ⁵‐phosphinoline.(III).

A novel photochemical reaction of a mixed phosphonium iodonium ylide with phenylacetylene as a route to diphenyl-1λ5-phosphinoline

A novel photochemical reaction of a mixed phosphonium iodonium ylide with phenylacetylene as a route to diphenyl-1λ5-phosphinoline

Heterocycles from Phosphonium−Iodonium Ylides. Photochemical Synthesis of λ5-Phosphinolines

A photochemical reaction of mixed phosphonium-iodonium ylides with acetylenes yielding lambda(5)-phosphinolines, a rare class of phosphorus heterocycles hardly accessible by other methods, was found. The yields of lambda(5)-phosphinolines vary from 35% to 80%. The structures of two phosphinolines were established by single-crystal X-ray diffraction. The X-ray diffraction and NMR spectra data indicate the superposition of ylidic and aromatic structures for phosphinolines.

Initiated pseudo-[3+2] cycloaddition of mixed phosphonium-iodonium ylides to acetonitrile

The oxazole fragment is involved as a structural unit in some biologically active compounds. A large number of oxazole containing compounds were isolated from vari ous natural sources, particularly, of the sea origin. Many of these compounds exhibit different activities, for example, antiviral, antifungal, and antibacterial activities.1,2 An analysis of the published data shows that there are no general approaches to the synthesis of 2,4 and 2,4,5 substituted oxazoles.3—5 Iodonium ylides hold prom ise as reagents for the synthesis of oxazoles.6,7 Recently, we have found that mixed phosphonium iodonium ylides 1 have different reactivities associated primarily with the existence of the enolate resonance form.8—10 An analysis of the structural features of ylide suggests that this compound can be used as a 1,3 dipole in the synthesis of furans 2 according to Scheme 1.

One-pot process in phosphonium-iodonium ylides: nucleophilic substitution and the Wittig reaction

The nucleophilic substitution in mixed phosphonium-iodonium ylides was investigated. The iodonium group is replaced by such S-containing nucleophiles as the thiocyanate anion or thiourea, as well as by halide ions. The structure of the reaction product with the thiocyanate ion was established by X-ray diffraction. A one-pot process involving the nucleophilic substitution and the Wittig reaction was developed.