Hypervalent Iodine in Synthesis

A new and facile method for the preparation of arenetellurinic mixed anhydrides is described from diaryl ditellurides and phenyliodine (III) dicarboxylates. Hydrolysis of the arenetellurinic mixed anhydrides gives arenetellurinic anhydrides and a one - pot procedure involving the reaction of diaryl ditellurides with phenyliodine (III) dicarboxylates in a two - phase system of methylene chloride and aqueous solution of sodium hydroxide for the preparation of arenetellurinic anhydrides is provided.     

A novel and direct synthesis of chroman derivatives using a hypervalent iodine(III) reagent

The direct aromatic carbon-oxygen bond-formation reaction was described and the novel and simple synthetic method for chroman derivatives involving aromatic cation radical intermediates was developed using the hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA).     

Mn(III)-mediated formal [3+3]-annulation of vinyl azides and cyclopropanols: a divergent synthesis of azaheterocycles

Mn(III)-mediated formal [3+3]-annulation has been developed using readily available vinyl azides and cyclopropanols with a wide range of substituents. Vinyl azides were successfully applied as a three-atom unit including one nitrogen to prepare pyridines and δ-lactams by the reactions with monocyclic cyclopropanols as well as to construct 2-azabicyclo[3.3.1] and 2-azabicyclo[4.3.1] frameworks with bicyclic cyclopropanols, bicyclo[3.1.0]hexan-1-ols, and bicyclo[4.1.0]heptan-1-ols. These reactions were initiated by a radical addition of β-carbonyl radicals, generated by the one-electron oxidation of cyclopropanols with Mn(III), to vinyl azides to give iminyl radicals, which cyclized with the intramolecular carbonyl groups. In addition, application of the present methodology to a synthesis of the quaternary indole alkaloid, melinonine-E, was accomplished.     

Total syntheses via cyclopropanols

Cyclopropanols are readily available via the Kulinkovich cyclopropanation, the Simmons-Smith reaction, and other synthetic methods. Due to their intrinsic ring stains, cyclopropanols and their derivatives are highly reactive and can be converted to different structural scaffolds which are frequently found in many natural products. In this review, we highlight the applications of various cyclopropanol ring opening/expansion/fragmentation reactions in the total syntheses of natural products.     

Nucleophilic attack of intramolecular hydroxyl groups on electron-rich aromatics using hypervalent iodine(III) oxidation

The hypervalent iodine(III) reagent, phenyliodine bis(trifluoroacetate) (PIFA)-mediated oxidative nucleophilic substitution of electron-rich aromatics involving aromatic cation radical intermediates was utilized in the direct aromatic carbon-oxygen bond formation reaction, and a novel and simple synthetic method for chroman derivatives was developed. As an extension of this methodology, a facile access to spirodienone derivatives was also achieved.     

Oxidation of 4-arylphenol trimethylsilyl ethers to p-arylquinols using hypervalent iodine(III) reagents

An efficient synthesis of p-arylquinols by the oxidation of 4-arylphenol trimethylsilyl ethers with phenyliodine(III) diacetate (PIDA) is reported. This protocol greatly improved the yield of p-quinol by minimizing oligomer side products compared to the oxidation of free phenol with hypervalent iodine(III) reagents. The innocuity of phenyliodine(III) diacetate associated with the mild conditions make the method highly competitive over metal-mediated oxidation reactions. The proposed reaction mechanism is discussed and compared to the generally accepted mechanism of 4-substituted phenols to explain the yield improvement.     

New Achievements in the Field of Intramolecular Phenolic Coupling Reactions,Using Hypervalent (III) Iodine Reagent: Synthesis of Galanthamine

Our investigations on the oxidative possibilities of the hypervalent iodine(III) reagent established that phenyliodine(III)bis(trifluoroacclate) (PIFA) can provide one-pot contiguous coupling-cyclization reaction giving a product with narwedine skeleton, when used in a phenolic coupling reaction of p'-bromonorbelladine derivatives. A suitably selected precursor gave up to 60% yield of the coupled product.     

Novel and direct oxidative cyanation reactions of heteroaromatic compounds mediated by a hypervalent iodine(III) reagent

The hypervalent iodine(III) reagent phenyliodine bis(trifluoroacetate) (PIFA) mediates the selective cyanation reactions of a wide range of electron-rich heteroaromatic compounds such as pyrroles, thiophenes, and indoles under mild conditions. These reactions proceed via a cation radical intermediate, and the key for the successful transformation presumably depends on the oxidation-reduction potential of the substrates used. The synthetic utility has been demonstrated through the conversion of these biologically important pyrroles 2f and 2g. [reaction: see text]     

Synthesis of N-substituted indole derivatives via PIFA-mediated intramolecular cyclization

[Structure: see text] A variety of N-arylated and N-alkylated indole derivatives were synthesized by way of a phenyliodine bis(trifluoroacetate) (PIFA)-mediated intramolecular cyclization. This novel method allows for the construction of an indole skeleton by joining the N-atom on the side chain to the benzene ring at the last synthetic step. Other novel pyrrole-fused aromatic compounds can also be achieved by this method.     

A new synthesis of dienone lactones using a combination of hypervalent iodine(III) reagent and heteropoly acid

The oxidation of non-phenolic alkanoic acid derivatives to oxygen heterocycles was investigated; a new oxidative route to dienone lactones has been developed using a combination of hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate)(PIFA), and heteropoly acid (HPA).     

A Significant Effect of Triflic Acid on the Hypervalent λn-Iodane-Mediated Fragmentation of the Tertiary Cyclopropanol System

Trifluoromethanesulfonic acid enhanced the ring cleavage in the reaction of silyl tertiary cyclopropyl ethers with phenyliodine(III) diacetate in a catalytic amount.     

A novel and efficient oxidative biaryl coupling reaction of phenol ether derivatives using a combination of hypervalent iodine(III) reagent and heteropoly acid

A novel and efficient oxidative biaryl coupling reaction of phenol ether derivatives using a combination of hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate) (PIFA), and heteropoly acid has been developed.     

Kinetic spectrophotometric determination of Fe(II) in the presence of Fe(III) by H-point standard addition method in mixed micellar medium

The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition.     

Pictet‐Spengler Condensation of N,N‐Dimethylsulfamoyl‐β‐Phenethylamines with Methylthioacetic Acid Ethyl Ester. New Synthesis of Ethyl 1,2,3,4‐Tetrahydroisoquinoline‐1‐Carboxylates

The reaction of N,N‐dimethylsulfamoyl‐β‐phenethylamines with methylthioacetic acid ethyl ester using phenyliodine(III) bis(trifluoroacetate) gives moderate to good yields of the corresponding ethyl 1,2,3,4‐tetrahydroisoquinoline‐1‐carboxylates.     

Phenyliodine(III) Triflate Mediated Synthesis of 5‐Benzoyldihydro‐2(3H)‐furanones

A direct and efficient method for the preparation of 5‐benzoyldihydro‐2(3H)‐furanones was realized by cyclization of 4‐benzoylbutyric acids in the presence of phenyliodine(III) triflate.     

Electrospray ionization collision‐induced dissociation mass spectrometry: a tool to characterize synthetic polyaminocarboxylate ferric chelates used as fertilizers

Fertilizers based on synthetic polyaminocarboxylate ferric chelates have been known since the 1950s to be successful in supplying Fe to plants. In commercial Fe(III)‐chelate fertilizers, a significant part of the water‐soluble Fe‐fraction consists of still uncharacterized Fe byproducts, whose agronomical value is unknown. Although collision‐induced dissociation (CID) tandem mass spectrometry (MS/MS) is a valuable tool for the identification of such compounds, no fragmentation data have been reported for most Fe(III)‐chelate fertilizers. The aim of this study was to characterize the CID‐MS² fragmentation patterns of the major synthetic Fe(III)‐chelates used as Fe‐fertilizers, and subsequently use this technique for the characterization of commercial fertilizers. Quadrupole‐time‐of‐flight (QTOF) and spherical ion trap mass analyzers equipped with an electrospray ionization (ESI) source were used. ESI‐CID‐MS² spectra obtained were richer when using the QTOF device. Specific differences were found among Fe(III)‐chelate fragmentation patterns, even in the case of positional isomers. The analysis of a commercial Fe(III)‐chelate fertilizer by high‐performance liquid chromatography (HPLC) coupled to ESI‐MS(QTOF) revealed two previously unknown, Fe‐containing compounds, that were successfully identified by a comprehensive comparison of the ESI‐CID‐MS²(QTOF) spectra with those of pure chelates. This shows that HPLC/ESI‐CID‐MS²(QTOF), along with the Fe(III)‐chelate fragmentation patterns, could be a highly valuable tool to directly characterize the water‐soluble Fe fraction in Fe(III)‐chelate fertilizers. This could be of great importance in issues related to crop Fe‐fertilization, both from an agricultural and an environmental point of view. Copyright © 2009 John Wiley & Sons, Ltd.     

Hypervalent Iodine(III) Mediated Synthesis of 2‐Substituted‐5‐Aryloxazoles

A direct and efficient method for the preparation of 2‐substituted‐5‐aryloxazoles was realized by reaction of aryl methyl ketones with various nitriles in the presence of phenyliodine(III) triflate.     

PIDA-mediated synthesis of oxazoles through oxidative cycloisomerization of propargylamides

PIDA [phenyliodine(III) diacetate] in AcOH or AcOH-HFIP (hexafluoroisopropanol) efficiently promotes the formation of 2,5-disubstituted oxazoles via the oxidative cycloisomerization of propargylamide derivatives.     

Asymmetric β-arylation of cyclopropanols enabled by photoredox and nickel dual catalysis

The enantioselective functionalization and transformation of readily available cyclopropyl compounds are synthetically appealing yet challenging topics in organic synthesis. Here we report an asymmetric β-arylation of cyclopropanols with aryl bromides enabled by photoredox and nickel dual catalysis. This dual catalytic transformation features a broad substrate scope and good functional group tolerance at room temperature, providing facile access to a wide array of enantioenriched β-aryl ketones bearing a primary alcohol moiety in good yields with satisfactory enantioselectivities (39 examples, up to 83% yield and 90% ee). The synthetic value of this protocol was illustrated by the concise asymmetric construction of natural product calyxolane B analogues.

An asymmetric β-arylation of cyclopropanols with aryl bromides was enabled by enantioselective photoredox and nickel dual catalysis.