Vinylphosphine Oxides Research Articles

Photocatalytic C(sp3)-P and C(sp2)-P Bond Formation via a Phosphorus Radical Cation.

A straightforward method for the phosphorylation of electron-deficient alkenes and aryl alkynes has been developed, leading to C(sp3)-P and C(sp2)-P bond formation. This process involves the generation of phosphorus radical cation intermediates through the photocatalyzed oxidation of ethyl diarylphosphinites. The coupling with electron-deficient alkenes encompasses a variety of heteroaromatics, including pyridine, (benzo)thiazole, and benzoxazole, as well as α,β-unsaturated esters and amides. Impressively, the coupling of radical cations with aryl alkynes demonstrated remarkable regioselectivity, thereby facilitating the synthesis of rare α-aryl vinyl phosphine oxides.

Regio- and stereoselective access to highly substituted vinylphosphine oxides via metal-free electrophilic phosphonoiodination of alkynes

In general, the P-centered ring-opening of quaternary phosphirenium salts (QPrS) predominantly leads to hydrophosphorylated products, while the C-centered ring-opening is primarily confined to intramolecular nucleophilic reactions, resulting in the formation of phosphorus-containing cyclization products instead of difunctionalized products generated through intermolecular nucleophilic processes. Here, through the promotion of ring-opening of three-member rings by iodine anions and the quenching of electronegative carbon atoms by iodine cations, we successfully synthesize β-functionalized vinylphosphine oxides by the P-addition of QPrS intermediates generated in situ. Multiple β-iodo-substituted vinylphosphine oxides can be obtained with exceptional regio- and stereo-selectivity by reacting secondary phosphine oxides with unactivated alkynes. In addition, a variety of β-functionalized vinylphosphine oxides converted from C-I bonds, especially the rapid construction of benzo[b]phospholes oxides, demonstrates the significance of this strategy.

Photoredox-catalyzed C(sp3)─H radical functionalization to enable asymmetric synthesis of α-chiral alkyl phosphine.

α-Chiral alkyl phosphines are privileged structural motifs with a wide application in organic and medical synthesis. It is highly desirable to develop stereoselective methods to prepare these enantioenriched molecules. The incorporation of C(sp3)─H functionalization and chiral phosphine chemistry is much less explored, probably because of the weak reactivity of C(sp3)─H bonds and/or the challenging site- and stereoselectivity issues. Herein, we disclose a synergistic catalysis system to enable an enantioselective radical addition process of α-substituted vinylphosphine oxides. An array of diverse α-chiral alkyl phosphors compounds is smoothly accessed by using the readily available chemicals as the inert C(sp3)─H bond reagent, such as sulfides, amines, alkenes, and toluene derivatives, exerting remarkable chemo-, site-, and enantioselectivity. On the basis of the mechanistic studies, both the C(sp3)─H bond activation and the stereochemistry-determining step are proposed to involve a single-electron transfer/proton transfer process.

Tandem addition of nucleophilic and electrophilic reagents to vinyl phosphinates: the stereoselective formation of organophosphorus compounds with congested tertiary carbons.

Carbon anions formed via the addition of Grignard reagents to SP-vinyl phosphinates were modified with electrophilic reagents to afford organophosphorus compounds with diverse carbon skeletons. The electrophiles included acids, aldehydes, epoxy groups, chalcogens and alkyl halides. When alkyl halides were used, bis-alkylated products were afforded. Substitution reactions or polymerization occurred when the reaction was applied to vinyl phosphine oxides.

Regioselective Synthesis of β-Silyl-Substituted Vinylphosphine Oxides via Copper-Catalyzed Protosilylation of Dialkynylphosphine Oxides

Regioselective Synthesis of <i>β</i>-Silyl-Substituted Vinylphosphine Oxides via Copper-Catalyzed Protosilylation of Dialkynylphosphine Oxides

Knoevenagel Condensation of Phosphinoylacetic Acids with Aldehydes: An Efficient One-Pot Strategy for the Synthesis of P-Functionalized Alkenyl Compounds

AbstractA wide range of commercially available aldehydes have been applied to Knoevenagel condensation reaction to give E-alkenylphosphine oxides and vinylphosphine oxides. The readily available phosphinoylacetic acids derived from P(O)–H compounds were used as the starting materials in the reaction, providing a highly stereoselective and efficient method for constructing α,β-unsaturated phosphine oxides. Moreover, this simple and practical procedure provides an alternative and more environmentally friendly synthesis strategy for this type of P-functionalized alkenyl compounds.

Cobaloxime Catalysis: Selective Synthesis of Alkenylphosphine Oxides under Visible Light.

Direct activation of H-phosphine oxide to react with an unsaturated carbon-carbon bond is a straightforward approach for accessing alkenylphosphine oxides, which shows significant applications in both synthetic and material fields. However, expensive metals and strong oxidants are typically required to realize the transformation. Here, we demonstrate the utility of earth-abundant cobaloxime to convert H-phosphine oxide into its reactive radical species under visible light irradiation. The radical species thus generated can be utilized to functionalize alkenes and alkynes without any external photosensitizer and oxidant. The coupling with terminal alkene generates E-alkenylphosphine oxide with excellent chemo- and stereoselectivity. The reaction with terminal alkyne yields linear E-alkenylphosphine oxide via neutral radical addition, while addition with internal ones generates cyclic benzophosphine oxides and hydrogen. Mechanistic studies on radical trapping experiments, electron spin resonance studies, and spectroscopic measurements confirm the formation of phosphinoyl radical and cobalt intermediates that are from capturing the electron and proton eliminated from H-phosphine oxide. The highlight of our mechanistic investigation is the dual role played by cobaloxime, viz., both as the visible light absorber to activate the P(O)-H bond as well as a hydrogen transfer agent to influence the reaction pathway. This synergetic feature of the cobaloxime catalyst preforming multiple functions under ambient condition provides a convergent synthetic approach to vinylphosphine oxides directly from H-phosphine oxides and alkenes (or alkynes).

4 + 2] Cycloaddition of Vinylphosphine Oxides to α-Oxy-o-xylylene as a route to Phosphorylated Naphthyl and Biaryl Scaffolds

α-Oxy- o-xylylene, a highly reactive diene readily accessible from benzocyclobutenol, undergoes Diels-Alder reaction with vinylphosphine oxides, yielding the corresponding 2-phosphorylated 1-hydroxy-1,2,3,4-tetrahydronaphthalenes in excellent yields. Use of unsubstituted and trans-2-aryl-substituted vinylphosphine oxides leads to cycloadducts with complete regioselectivity and with cis/trans selectivity up to 19:1 in the most favorable case. In the case of P-stereogenic trans-2-aryl-substituted vinylphosphine oxides, a virtually complete chirality transfer from P to C can be achieved. Dehydration and aromatization of the obtained cycloadducts bearing the resolved P-stereogenic phosphinoyl groups can be carried out to afford the valuable P-stereogenic and axially chiral phosphorylated 1,2'-binaphthyl ring system. Cases of restricted rotation around Csp3-Csp2 single bond in some tetrahydronaphthalene cycloadducts have also been revealed.

Reactivity of allenylphosphonates/allenylphosphine oxides – some new addition/cycloaddition and cyclization pathways

Abstract In this paper, we highlight some addition/cycloaddition reactions of allenylphosphonates and allenylphosphine oxides, mostly based on the work done in our laboratory. Thus the electrophilic addition of iodine monochloride (ICl) with allenylphosphine oxides affords cyclic phosphonium salts rather than γ-chloro-β-iodovinylphosphine oxides (NMR, HRMS, X-ray) that exhibit rather unusual downfield shifts in the 31P NMR spectra. These compounds undergo hydrolysis to afford γ-hydroxy-β-iodovinylphosphine oxides; the hydroxymethyl group in these compounds can be oxidized by Dess-Martin periodinane to afford the corresponding aldehyde-substituted vinylphosphine oxides. A [2+2] cycloaddition product of an allenylphosphonate has also been structurally characterized. Other reactions that are highlighted include those leading to (Z)/(E)-β-aminovinylphosphonates, β-ketophosphonates (and their utility in Horner-Wadsworth-Emmons reaction), indolyl/furanyl/isocoumaranyl/naphthyl phosphine oxides, thiophosphorylated phosphonates and azo-substituted coumarin phosphonates.

New reactions of allenes, alkynes, ynamides, enynones and isothiocyanates

This perspective article is related to transformations (both catalytic and non-catalytic) involving allenes, alkynes/enynones/ynamides and isothiocyanates. Part of the work from the author’s group has been reviewed along with some new reactions of (i) allenylphosphonate/allenylphosphine oxide and (ii) a P(III) isothiocyanate. Thus, the allenylphosphine oxide $$\hbox {Ph}_{2}\hbox {P(O)C(Ph)=C=CH}_{2}$$ undergoes base (DBU) catalyzed addition to the $$\beta $$ -ketophosphonate $$\hbox {(OCH}_{2}\hbox {CMe}_{2}\hbox {CH}_{2}\hbox {O)P(O)CH}_{2}\hbox {C(O)CH}_{3}$$ at $$90\,{^{\circ }}\hbox {C}$$ to afford the addition product $$\hbox {Ph}_{2}\hbox {P(O)C(Ph)=C(Me)CH[C(O)Me][P(O)(OCH}_{2}\hbox {CMe}_{2}\hbox {CH}_{2}\hbox {O)]}$$ . In an analogous reaction, with DBU as the base at $$140\;{^{\circ }}\hbox {C}$$ , isomeric vinylphosphine oxides (Z)- $$\hbox {Ph}_{2}\hbox {P(O)C(Ph)=C(Me)CH}_{2}\hbox {[C(O)Me]}$$ and (E)- $$\hbox {Ph}_{2}\hbox {P(O)C(Ph)=C(Me)CH}_{2}\hbox {[C(O)Me]}$$ were isolated. The E-isomer has been characterized by single crystal X-ray structure determination. In another set of studies, the reaction of P(III) isothiocyanate $$\hbox {(OCH}_{2}\hbox {CMe}_{2}\hbox {CH}_{2}\hbox {O)P(NCS)}$$ with N-(2-bromomethyl)sulfonamide afforded an unusual product with the formula $$\hbox {(OCH}_{2}\hbox {CMe}_{2}\hbox {CH}_{2}\hbox {O)P(O)SCH}_{2}\hbox {CH}_{2}\hbox {NHS(O)}_{2}$$ - $$(\hbox {C}_{6}\hbox {H}_{4}$$ -4- $$\hbox {Me)}$$ as shown by X-ray structure determination. This result is different from that obtained in the recently reported analogous reaction using phenyl isothiocyanate. Synopsis. Base-catalyzed the addition of $$\beta $$ -ketophosphonate or ethyl acetoacetate to allenylphosphine oxide affords vinylphosphine oxides; in the latter case, elimination of the ester group also takes place. It is also shown that reactivity of a P(III) isothiocyanate is different from that of organic isothiocyanates.

Synthesis of 2,3-dihydro-1H-phosphindole-1-oxides via the t-BuLi-mediated rearrangement of vinyl bromides and phosphine oxides

We report an intramolecular vinyllithium addition to phosphine oxides, and discovered an unexpected rearrangement to form unique cyclic phosphine oxides.

Reaction of vinyl- and allenylphosphorylated compounds with cytisine in aqueous medium

We have shown for the first time that the alkaloid cytisine can be easily involved in the reaction of nucleophilic addition with certain unsaturated phosphoryl compounds including vinylphosphonate, vinyl phosphine oxide, allenylphosphonates, and allenyl phosphine oxides in aqueous medium.

Unusual Course of the Reaction of Allyl Phosphine Oxides with the Grundmann Ketone

This article describes efficient preparation of isomeric allyl phosphine oxides possessing a protected cyclohexanediol fragment. Their base-catalyzed interconversions are examined and reactions with the Grundmann ketone provide an adduct containing the rearranged vinyl phosphine oxide moiety, instead of 19-norvitamin D3 analogs, the expected products of the Horner–Wittig process.

Fragmentation of Carbohydrate Anomeric Alkoxyl Radicals: Synthesis of Chiral Polyhydroxylated β‐Iodo‐ and Alkenylorganophosphorus(V) Compounds

AbstractA direct approach to β‐iodophosphonates and β‐iodophosphine oxides from 2,3‐dideoxy‐3‐phosphoryl carbohydrate derivatives has been achieved by using the anomeric alkoxyl radical 1,2‐fragmentation protocol. The reaction has been conducted on carbohydrate derivatives under mild conditions with (diacetoxyiodo)benzene and molecular iodine. Subsequent dehydroiodination afforded the corresponding vinylphosphonates and vinylphosphine oxides.

Reaction of Tri(2‐pyridyl)phosphine with Electron‐Deficient Alkynes in Water: Stereoselective Synthesis of Functionalized Pyridylvinylphosphine Oxides

AbstractThe reaction of tri(2‐pyridyl)phosphine with electron‐deficient alkynes in water proceeds under mild conditions (40–45 °C, without catalyst, 4–5 h) with liberation of pyridine to give (E)‐pyridylvinylphosphine oxides in 45–56 % yields, the only exception being the reaction with cyanophenylacetylene, which affords the corresponding vinylphosphine oxide of Z‐configuration in 40 % yield. The reaction is likely triggered by the zwitterion, the adduct of tri(2‐pyridyl)phosphine to the electrophilic acetylenes, the carbanionic center of which is then neutralized by a proton from water. The intermediate phosphonium hydroxide finally decomposes to the product.

Synthesis of Chiral β-Iodo- and Vinylorganophosphorus(V) Compounds by Fragmentation of Carbohydrate Anomeric Alkoxyl Radicals

A new general methodology for the synthesis of chiral vinylphosphonate and vinylphosphine oxide carbohydrate derivatives has been developed using the anomeric alkoxyl radical fragmentation reaction as the key step. The synthetic sequence proceeded via β-iodophosphonate and β-iodophosphine oxide intermediates, which may be interesting synthons for the introduction of phosphorus into organic molecules. These vinylphosphonates could be easily transformed into 2-methylene-1-phosphapentofuranoses (3-methylene-1,2-oxaphospholanes) and β-aminophosphonates, isosteres of biologically active α-methylene-γ-lactones and β-amino acids, respectively.

ChemInform Abstract: Reaction of Olefins with Dimethyl(methylthio)sulfonium Salts in the Presence of Triphenylphosphine. Preparation of Vinylphosphonium Salts.

Olefins were effectively converted into the corresponding (2-methylthioalkyl)triphenylphosphonium salts by the reaction with dimethyl(methylthio)sulfonium salts in the presence of triphenylphosphine. 2-Triphenylphosphonioalkyldimethylsulfonium salts, synthesized by alkylation of the corresponding methylthiophosphonium salts, react with 1,8-diazabicyclo[5.4.0]undec-7-ene or aq NaOH to afford the corresponding vinylphosphonium salts or vinylphosphine oxides in good yields.

ChemInform Abstract: Electronic Structure and Conformational Properties of Vinylphosphonic Acid and Some Related Derivatives

The electronic structure and conformational properties of vinylphosphonic acid, vinylphosphoryl dichloride, and vinylphosphine oxide have been studied by ab initio quantum mechanical methods. Furthermore, the vinylphosphonic acid has been studied experimentally by means of 13 C NMR and ultraviolet spectroscopy. This compound has been synthesized by a modification of the McKenna hydrolysis reaction, improving significantly the yield. The ab initio calculations have been performed with different basis sets, including correlation energy at the MP2/6-31G * level. Topological analysis of charge density has also been carried out. Two conformers, s-cis and s-trans-gauche, have been determined for the internal rotation around the C-P bond, with low rotational barriers

ChemInform Abstract: Synthesis of Vinylphosphine Oxides: Vinyl Selenides as Vinylating Agents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of vinylphosphine oxides: vinyl selenides as vinylating agents

2-(Alkylselanyl)ethyl(diorgano)phosphine selenides readily accessible from secondary phosphine selenides and alkyl vinyl selenides react with aqueous solution of hydrogen peroxide to form vinylphosphine oxides in high yields.