Insertion of Arynes into P-O Bonds: One-Step Simultaneous Construction of C-P and C-O Bonds

Aryne Chemistry: Generation Methods and Reactions Incorporating Multiple Arynes

Arynes hold significance for the efficient fusion of (hetero) arenes with diverse substrates, advancing the construction of complex molecular frameworks. Employing multiple equivalents of arynes is particularly effective in the rapid formation of polycyclic cores found in optoelectronic materials and bioactive compounds. However, the inherent reactivity of arynes often leads to side reactions, yielding unanticipated products and underlining the importance of a detailed investigation into the use of multiple arynes to fine-tune their reactivity. This review centers on methodologies and syntheses in organic reactions involving multiple arynes, categorizing based on mechanisms like cycloadditions, σ-bond insertions, nucleophilic additions, and ene reactions, and discusses aryne polymerization. The categorization based on these mechanisms includes two primary approaches: the first entails multiple aryne engagement within a single step while the second approach involves using a single equivalent of aryne sequentially across multiple steps, with both requiring strict reactivity control to ensure precise aryne participation in each respective step. Additionally, the review provides an in-depth analysis of the selection of aryne precursors, organized chronologically and by activation strategy, offering a comprehensive background that supports the main theme of multiple aryne utilization. The expectation remains that this comprehensive review will be invaluable in designing advanced syntheses engaging multiple arynes.

o-Hydroxyarylphosphanes: Strategies for Syntheses of Configurationally Stable, Electronically and Sterically Tunable Ambiphiles with Multiple Applications

o-Hydroxyarylphosphanes are fascinating compounds by their multiple-reactivity features, attributed to the ambident hard and soft Lewis- and also Brønstedt acid-base properties, wide tuning opportunities via backbone substituents with ±mesomeric and inductive, at P and in o-position to P and O also steric effects, and in addition, the configurational stability at three-valent phosphorus. Air sensitivity may be overcome by reversible protection with BH3 , but the easy oxidation to P(V)-compounds may also be used. Since the first reports on the title compounds ca. 50 years ago the multiple reactivity has led to versatile applications. This includes various P-E-O and P=C-O heterocycles, a multitude of O-substituted derivatives including acyl derivatives for traceless Staudinger couplings of biomolecules with labels or functional substituents, phosphane-phosphite ligands, which like the o-phosphanylphenols itself form a range of transition metal complexes and catalysts. Also main group metal complexes and (bi)arylphosphonium-organocatalysts are derived. Within this review the various strategies for the access of the starting materials are illuminated, including few hints to selected applications.

Non-Hydrolysable Analogues of Cyclic and Branched Condensed Phosphates: Chemistry and Chemical Proteomics

Studies into the biology of condensed phosphates almost exclusively cover linear polyphosphates. However, there is evidence for the presence of cyclic polyphosphates (metaphosphates) in organisms and for enzymatic digestion of branched phosphates (ultraphosphates) with alkaline phosphatase. Further research of non-linear condensed phosphates in biology would profit from interactome data of such molecules, however, their stability in biological media is limited. Here we present syntheses of modified, non-hydrolysable analogues of cyclic and branched condensed phosphates, called meta- and ultraphosphonates, and their application in a chemical proteomics approach using yeast cell extracts. We identify putative interactors with overlapping hits for structurally related capture compounds underlining the quality of our results. The datasets serve as starting point to study the biological relevance and functions of meta- and ultraphosphates. In addition, we examine the reactivity of meta- and ultraphosphonates with implications for their "hydrolysable" analogues: Efforts to increase the ring-sizes of meta- or cyclic ultraphosphonates revealed a strong preference to form trimetaphosphate-analogue structures by cyclization and/or ring-contraction. Using carbodiimides for condensation, the so far inaccessible dianhydro product of ultraphosphonate, corresponding to P4 O11 2- , was selectively obtained and then ring-opened by different nucleophiles yielding modified cyclic ultraphosphonates.

Synthesis of Phosphachromones by Cyclized Coupling of Ethyl Hydrogen (Phenylethynyl)phosphonate with Arynes

A straightforward and efficient strategy for the synthesis of phosphachromones has been reported via the insertion of arynes into P-O bonds. This operationally simple reaction is compatible with different functional groups, affording various phosphachromones by the simultaneous formation of C-P and C-O bonds in one step with moderate to good yields, and the Fries rearrangement involving phosphorus atoms is a key step in the reaction.

Three-Component Coupling Reactions Involving Arynes, Phosphites, and Aldehydes toward 3-Mono-Substituted Benzoxaphosphole 1-Oxides

A mild, efficient, and transition-metal-free three-component coupling reaction involving arynes, phosphites, and aldehydes was established to afford 3-mono-substituted benzoxaphosphole 1-oxides. A range of 3-mono-substituted benzoxaphosphole 1-oxides was obtained from both aryl- and aliphatic-substituted aldehydes in moderate to good yields. Moreover, the synthetic utility of the reaction was demonstrated by a Gram-scale reaction and the transformation of the products into various P-containing bicycles.

The Aryne Phosphate Reaction

Condensed phosphates are a critically important class of molecules in biochemistry. Non-natural analogues are important for various applications, such as single-molecule real-time DNA sequencing. Often, such analogues contain more than three phosphate units in their oligophosphate chain. Consequently, investigations into phosphate reactivity enabling new ways of phosphate functionalization and oligophosphorylation are essential. Here, we scrutinize the potential of phosphates to act as arynophiles, paving the way for follow-up oligophosphorylation reactions. The aryne phosphate reaction is a powerful tool to-depending on the perspective-(oligo)phosphorylate arenes or arylate (oligo-cyclo)phosphates. Based on Kobayashi-type o-silylaryltriflates, the aryne phosphate reaction enables rapid entry into a broad spectrum of arylated products, like monophosphates, diphosphates, phosphodiesters and polyphosphates. The synthetic potential of these new transformations is demonstrated by efficient syntheses of nucleotide analogues and an unprecedented one-flask octaphosphorylation.

The Hydrolysis of Phosphinates and Phosphonates: A Review

Phosphinic and phosphonic acids are useful intermediates and biologically active compounds which may be prepared from their esters, phosphinates and phosphonates, respectively, by hydrolysis or dealkylation. The hydrolysis may take place both under acidic and basic conditions, but the C-O bond may also be cleaved by trimethylsilyl halides. The hydrolysis of P-esters is a challenging task because, in most cases, the optimized reaction conditions have not yet been explored. Despite the importance of the hydrolysis of P-esters, this field has not yet been fully surveyed. In order to fill this gap, examples of acidic and alkaline hydrolysis, as well as the dealkylation of phosphinates and phosphonates, are summarized in this review.

Recent Progress in the Selective Functionalization of P(O)-OH Bonds

As we all know, organic phosphorus compounds have high application values in chemical industries. Compared with traditional compounds with P-X (X = Cl, Br, I) and P-H bonds, phosphorylation reagents containing P(O)-OH bonds are stable, environmentally friendly, and inexpensive. However, in recent years, there have been few studies on the selective functionalization of P(O)-OH bonds for the fabrication of P-C and P-Z bonds. In general, four-coordinated P(O)-OH compounds have reached coordination saturation due to the phosphorus atom center, but cannot evolve the phosphorus coordination center through intra-molecular tautomerization; however, the weak coordination effects between the P=O bond and transition metals can be utilized to activate P(O)-OH bonds. This review highlights the most important recent contributions toward the selective functionalization of P(O)-OH bonds via cyclization/cross coupling/esterification reactions using transition metals or small organic molecules as the catalyst.

Synthesis of Aryldiphenylphosphine Oxides by Quaternization of Tertiary Diphenylphosphines with Aryl Bromides Followed by the Wittig Reaction

A two-step method for the synthesis of aryldiphenylphosphine oxides from tertiary diphenylphosphines and aryl bromides is developed. The first step is the quaternization of methyldiphenylphosphine or benzyldiphenylphosphine with aryl bromides. This quaternization can be nickel-catalyzed (metal-free in some cases), and tolerate of a variety of functional groups, furnishing quaternary phosphonium salts in 48-90% yields. The second step is Wittig reactions of these quaternary phosphonium salts with furan-2-carbaldehyde or p-chlorobenzaldehyde to provide aryldiphenylphosphine oxides in 27-90% yields. The use of the Wittig reaction for the synthesis of tertiary phosphine oxides is in contrast to its traditional use for the synthesis of olefins, leaving tertiary phosphine oxide as a byproduct. This quaternization-Wittig method can be applied to synthesize aryldiphenylphosphine oxides that are difficult to access by the alkaline hydrolysis of aryltriphenylphosphonium salts, especially those bearing an electron-deficient aryl group. The ligand-coupling mechanism for the alkaline hydrolysis of (p-acylphenyl)triphenylphosphonim salts is also discussed.

Direct synthesis of 2-substituted benzonitriles via alkylcyanation of arynes with N,N-disubstituted aminomalononitriles

An efficient alkylcyanation of in situ generated arynes by N,N-disubstituted aminomalononitriles is described, enabling the direct synthesis of 2-substituted benzonitriles.

Direct synthesis of ortho-methylthio allyl and vinyl ethers via three component reaction of aryne, activated alkene and DMSO

A transition-metal free synthetic strategy for the direct synthesis of ortho-methylthio allyl and vinyl ethers via cascade three-component coupling of aryne, activated alkene and DMSO.

Recent advances in the synthesis of organophosphorus compounds via Kobayashi's aryne precursor: a review

This review systematically summarizes the progress in aryne chemistry for the synthesis of organophosphorus compounds via aryne insertion into the C–P, P–N, P–P, P–O, PP, PN and PS bonds.

Synthesis of 6-substituted indoloquinazolinones from arynes and 2-acyl-4-quinazolinones: a transition-metal free C–N and C–C bond formation strategy

A versatile transition-metal free synthetic strategy has been developed for the direct synthesis of 6-substituted indoloquinazolinones from 2-acyl-4-quinazolinones and aryne precursors. This cascade strategy proceeds via successive C–N and C–C bond formation in a single reaction vessel.

Photoredox/Cobalt-Catalyzed Phosphinyloxy Radical Addition/Cyclization Cascade: Synthesis of Phosphaisocoumarins

A novel visible-light photoredox-catalyzed phosphinyloxy radical addition/cyclization cascade of arylphosphinic acids or arylphosphonic acid monoesters with alkynes has been developed, which provides an efficient and practical access to various phosphaisocoumarins by using a dual catalytic system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst [Co(dmgH)₂]PyCl at ambient temperature. This method has advantages of a broad substrate scope, mild condition, as well as no sacrificial oxidant.

Aryne insertion into the PO bond: one-pot synthesis of quaternary phosphonium triflates

A novel transition-metal free synthetic strategy for the direct synthesis of quaternary phosphonium triflates via insertion of aryne into phosphine oxide.

Zinc-catalyzed regioselective C–P coupling of p-quinol ethers with secondary phosphine oxides to afford 2-phosphinylphenols

A highly regioselective C–P coupling reaction of p-quinol ethers with secondary phosphine oxides is developed as a new synthesis method for 2-phosphinylphenols by using Zn(OTf)₂ as the catalyst.

Manganese(iii)-mediated selective phosphorylation of enamides: direct synthesis of β-phosphoryl enamides

Mn(iii)-Mediated radical oxidative selective phosphorylation ofN-styrylamides to afford β-phosphoryl enamides, which could be easily transformed to β-amino phosphonic acids, is described.

A cascade process for the synthesis of ortho-formyl allyl aryl ethers and 2H-chromen-2-ol derivatives from arynes via trapping of o-quinone methide with an activated alkene

A transition-metal free synthetic strategy for the direct synthesis of ortho-formyl substituted allyl aryl ethers and 2H-chromen-2-ol derivatives via a cascade three-component coupling of arynes, activated alkene and N,N-dimethylformamide.

Transition-metal free C(sp2)–C(sp2) bond formation: arylation of 4-aminocoumarins using arynes as an aryl source

A mild, efficient and transition-metal free synthetic strategy has been developed for the α-arylation of 4-aminocoumarins using arynes as an aryl source. This synthetic strategy proceeds via C(sp²)–C(sp²) bond formation between 4-aminocoumarins and aryne precursors in a single step in the absence of a metal-catalyst.

Tandem Diels-Alder/oxidation-aromatization reactions involving 2-styrylchromones and arynes

Transition-metal-free Diels-Alder and tandem Diels-Alder/oxidation-aromatization reactions of 2-styrylchromones with arynes have been demonstrated under mild reaction conditions with a wide range of substrates. The tandem process afforded functionalized benzo[c]xanthone derivatives in moderate to good yields. This efficient protocol allows rapid access to either dihydrobenzo[c]xanthone and benzo[c]xanthone derivatives selectively by simply changing the atmosphere of the reaction.

Stevens rearrangement of thioethers with arynes: a facile access to multi-substituted β-keto thioethers

An effective method for the synthesis of multi-substituted β-keto thioethers via Stevens rearrangement of simple β-keto thioethers with arynes has been developed. In these reactions, successive C-S/C-H/C-C bonds were formed in one pot under mild and transition-metal free conditions to afford multi-substituted β-keto thioethers in moderate to good yields.

Synthesis of fused benzimidazoles via successive nucleophilic additions of benzimidazole derivatives to arynes under transition metal-free conditions

An expedient and efficient strategy was developed for the synthesis of benzimidazole derivatives from aryne precursors under transition metal-free conditions.

Diversity-Oriented Synthesis of Spiroannulated Benzofuran-3-one Scaffold of Leptosphaerin C and Congeners via Aryne Insertion

A concise synthesis of functionalized cyclohexenone-fused spirobenzofuran-3-ones under mild reaction conditions was developed. The reaction proceeds via insertion of aryne into the C-O bond followed by a regioselective intramolecular conjugate addition. The use of silyl-protected acid was crucial for the transformation. This protocol was successfully applied for the synthesis of leptosphaerin C core and its novel analogues.

Synthesis of o-Aryloxy Triarylsulfonium Salts via Aryne Insertion into Diaryl Sulfoxides

The aryne insertion into "S═O" bond has been validated recently. This technology is elusively applied to the synthesis of thioethers. In contrast to the reported cases, the reaction described furnished o-aryloxy triarylsulfonium salts, in lieu of thioethers, in good to excellent yields. The reaction is also featured by its exquisite regioselectivity, broad substrate scope, and mild conditions (25 °C). Preliminary mechanistic studies suggest that the reaction probably proceeds in a sequential [2 + 2] cycloaddtion/O-arylation/protonation pathway.