Chiral Hypervalent Iodine Reagents Research Articles

Iodine(III)-Mediated Enantioselective Oxidative Contraction of Dihydropyranones.

The γ-butyrolactone motif is promising in pharmaceuticals and natural products with various biological activities. The oxidative contraction of dihydropyranones mediated by hypervalent iodine (HVI) reagents is an efficient approach of preparing this motif. We show that, using readily available chiral HVI reagents, numerous enantioenriched γ-butyrolactones are accessible. The method provides generally high enantioselectivities and modest to high yields. The resulting chiral iodoarene is easily recovered and reused for the reaction multiple times, without loss of yield or enantioselectivities.

Recent Advances in Asymmetric Dearomatization Reactions Induced by Chiral Hypervalent Iodine Reagents

Recent Advances in Asymmetric Dearomatization Reactions Induced by Chiral Hypervalent Iodine Reagents

Iodine(III)-Based Hypervalent Iodine Electrophiles in Organic Synthesis

Abstract: The chemistry of hypervalent iodine reagents is now developed as an important tool of synthetic organic chemistry. These reagents play a key role in replacing the toxic heavy metal reagent because of their mild reaction condition and environmentally friendly nature. Mainly, these reagents were known for oxidative properties, but the scope of these reagents is not limited to oxidation reactions. In the past two decades, they have been used as versatile electrophiles in various key organic transformations. Recently, the demand for these reagents has increased drastically for green chemistry, mainly due to their application in catalysis. Hypervalent iodine reagents have been successfully used to develop various oxidative transformations such as the oxidation of different organic species, α-functionalization of carbonyl compounds, cyclization reactions, C-H activation reactions, lactonization and oxidative rearrangements. Moreover, the use of these reagents is not limited to general organic reactions but is successfully used to develop several stereoselective transformations by using chiral hypervalent iodine reagents. This review article highlights various acyclic and cyclic reactions where the hypervalent iodine reagents have been used as electrophiles.

Chiral Ligands in Hypervalent Iodine Compounds: Synthesis and Structures of Binaphthyl-Based λ3 -Iodanes.

Several novel binaphthyl-based chiral hypervalent iodine(III) reagents have been prepared and structurally analysed. Various asymmetric oxidative reactions were applied to evaluate the reactivities and stereoselectivities of those reagents. Moderate to excellent yields were observed; however, very low stereoselectivities were obtained. NMR experiments indicated that these reagents are very easily hydrolysed in either chloroform or DMSO solvents leading to the limited stereoselectivities. It is concluded that the use of chiral ligands is an unsuccessful way to prepare efficient stereoselective iodine(III) reagents.

Sulfur-Based Chiral Iodoarenes: An Underexplored Class of Chiral Hypervalent Iodine Reagents

AbstractChiral hypervalent iodine reagents are active players in modern stereoselective organic synthesis. Structurally diverse chiral hypervalent iodine reagents have been synthesised and extensively studied, but hypervalent iodine reagents containing chiral sulfur stereogenic centre are scarce and their synthesis is challenging. A small library of iodoarenes containing chiral sulfinamide and chiral sulfoximine moieties has been synthesised using commercially available reagents. The oxidation of the chiral iodoarene precursors to iodine(III) reagents was cumbersome due to facile overoxidation of the sulfoxide moiety and hence loss of chirality under various oxidation conditions. Oxidation of chiral sulfonimidoyl derivatives to the corresponding hypervalent iodine reagents was successful and led to novel sulfur-based chiral iodine(III) reagents.

Recent Advances in Asymmetric Functionalization of Olefins Induced by Chiral Hypervalent Iodine Reagents

The functionalization of olefins induced by chiral hypervalent iodine reagents is a basic method for obtaining enantiomerically enriched chiral molecules and biologically active natural products. It is one of the new and promising fields in asymmetric synthesis. Throughout the past 20 years development in this area, on the one hand, stereoselective functionalizations of alkenes such as disulfonyloxylation, diacetoxylation, dihalogenation, diamination, hydroxylation-sulfonyloxylation and halogenation-alkylation and carbonylation have been successfully achieved with chiral hypervalent iodine reagents through intermolecular reactions, in which various functionalized products were enantioselectively obtained. On the other hand, many of hetero-cyclic compounds such as γ-butyrolactones, chromans, isochromans, oxazolidinones, piperidines, pyrrolidines and aziridines can be synthesized by intramolecular oxidative lactonization, etherification, amidation, arylation and other reactions, in which hypervalent iodine reagents can provide efficient methods for the synthesis of chiral heterocyclic compounds. In addition, various functionalization reactions of olefins mediated by chiral hypervalent iodine reagents can afford target compounds with excellent yield and enantioselectivity. Thus, this methodology has also been used in the total synthesis of natural products. The functionalization of olefins induced by chiral hypervalent iodine reagents and their applications in the total synthesis of natural products are reviewed.

Recent Application of Chiral Aryliodine Based on the 2-Iodo­resorcinol Core in Asymmetric Catalysis

AbstractChiral iodoarenes have been steadily increasing in importance in recent years, especially in enantioselective synthesis and catalysis. Since the development of the concept of chiral iodine(I/III) catalysis, the use of various chiral aryliodine frameworks has been explored in this area. This short review gives an overview of the use of chiral hypervalent iodine(I/III) reagents based on the 2-iodoresorcinol core with two attached two lactic side chains bearing ester or amide groups for the catalytic enantioselective dearomatization of phenol compounds, asymmetric oxidation of alkenes, and enantioselective α-functionalization of carbonyl compounds highlighting the excellent reactivities in terms of yield and enantioselectivity.1 Introduction2 Enantioselective Dearomatization of Phenol Derivatives3 Asymmetric Oxidation of Alkenes4 Enantioselective α-Functionalization of Carbonyl Compounds5 Conclusion and Outlook

Alkene Difunctionalization Using Hypervalent Iodine Reagents: Progress and Developments in the Past Ten Years.

Hypervalent iodine reagents are of considerable relevance in organic chemistry as they can provide a complementary reaction strategy to the use of traditional transition metal chemistry. Over the past two decades, there have been an increasing number of applications including stoichiometric oxidation and catalytic asymmetric variations. This review outlines the main advances in the past 10 years in regard to alkene heterofunctionalization chemistry using achiral and chiral hypervalent iodine reagents and catalysts.

Structurally Defined α-Tetralol-Based Chiral Hypervalent Iodine Reagents.

A novel class of chiral hypervalent iodine reagents containing an α-tetralol scaffold is introduced. Iodine triacetate is employed in a key step as a highly selective and efficient iodinating reagent for a short and convenient synthesis of iodine(III) derivatives. Solid-state X-ray analyses offer valuable structural information, while reactivities and stereoselectivities are investigated in three model reactions.

Asymmetric syntheses and applications of planar chiral hypervalent iodine(V) reagents with crown ether backbones

Novel optically active hypervalent iodine(V) reagents with planar chiral crown ether backbones were synthesized using the intramolecular Huisgen reaction as a key step and l-methyl lactate as the source of chirality. The relative configurations of these reagents and stabilities of planar chiralities were determined by DFT calculations. These planar chiral reagents were applied to the hydroxylative dearomatization/[4 + 2]-dimerization reactions of phenols to afford bisthymol and biscarvacrol, a natural product, with moderate enantioselectivities.

Oxidative Cyclization of Naphtholic Sulfonamides Mediated by a Chiral Hypervalent Iodine Reagent: Asymmetric Synthesis versus Resolution

A chiral aryl iodide promotes the enantioselective oxidative cyclization of 1-naphtholic sulfonamides, albeit in moderate ee and low yield. The products tend to crystallize as conglomerates. Recrystallization thus increases their ee to > 99% ee. This highly enantioenriched material provides seed crystals for the resolution of the racemate (prepared in high yield by oxidative cyclization with (diacetoxyiodo)benzene in trifluoroacetic acid) by coupled preferential crystallization. This enables the production of significant quantities of highly enantioenriched products, despite the low efficiency of the enantioselective reaction.

Oxidative Kinetic Resolution of Some Naphtholic Alcohols Mediated by a Chiral Hypervalent Iodine Reagent

A chiral aryl iodide enables the catalytic, oxidative kinetic resolution of various 2-[(3-hydroxy-2-alkyl)propyl]naphthalen-1-ols.

A survey of chiral hypervalent iodine reagents in asymmetric synthesis.

The recent years have witnessed a remarkable growth in the area of chiral hypervalent iodine chemistry. These environmentally friendly, mild and economic reagents have been used in catalytic or stoichiometric amounts as an alternative to transition metals for delivering enantioenriched molecules. Varieties of different chiral reagents and their use for demanding asymmetric transformations have been documented over the last 25 years. This review highlights the contribution of different chiral hypervalent iodine reagents in diverse asymmetric conversions.

Electron-Deficient Chiral Lactic Acid-Based Hypervalent Iodine Reagents.

Novel electron-deficient chiral hypervalent iodine reagents were prepared in good overall yields. The reactivity and stereoselectivity of these reagents in oxidative rearrangements of alkenes to α-aryl ketones were investigated. The results show that the new reagents have good reactivity and generate products with high enantiomeric excess.

Asymmetric Oxidative Cycloetherification of Naphtholic Alcohols.

The catalytic, enantioselective oxidative cyclization of naphthol-derived carboxylic acids mediated by chiral hypervalent iodine reagents has been studied extensively in the recent past, but analogous reactions of non-carboxylic substrates are yet unknown. This paper describes a catalytic, enantioselective, hypervalent iodine-promoted oxidative cycloetherification reaction of naphtholic alcohols. The new process relies on a variant of the Uyanik-Ishihara catalyst, in which the stereogenic centers have been relocated closer to the iodine atom. The new catalyst design affords optical yields comparable to those available with Uyanik-Ishihara iodides, but chemical yields are sensibly higher, at least with the tests substrates. An even more problematic reaction is the catalytic, enantioselective oxidative cyclization of naphtholic sulfonamides. In this case, the new catalyst affords significantly higher optical inductions than Uyanik-Ishihara iodides. The kinetic resolution of particular naphtholic alcohols is demonstrated. The absolute configuration of a numver of enantioenriched compounds obtained in this study was ascertained by X-ray diffractometry.

Metal‐Free Enantioselective Oxidative Arylation of Alkenes: Hypervalent‐Iodine‐Promoted Oxidative C−C Bond Formation

AbstractThe enantioselective oxyarylation of (E)‐6‐aryl‐1‐silyloxylhex‐3‐ene was achieved using a lactate‐based chiral hypervalent iodine(III) reagent in the presence of boron trifluoride diethyl etherate. The silyl ether promotes the oxidative cyclization, and enhances the enantioselectivity. In addition, the corresponding aminoarylation was achieved.

Metal-Free Enantioselective Oxidative Arylation of Alkenes: Hypervalent-Iodine-Promoted Oxidative C-C Bond Formation.

The enantioselective oxyarylation of (E)-6-aryl-1-silyloxylhex-3-ene was achieved using a lactate-based chiral hypervalent iodine(III) reagent in the presence of boron trifluoride diethyl etherate. The silyl ether promotes the oxidative cyclization, and enhances the enantioselectivity. In addition, the corresponding aminoarylation was achieved.

Facile synthesis of amino acid-derived novel chiral hypervalent iodine(V) reagents and their applications

Amino acid-derived novel chiral hypervalent iodine(V) reagents were synthesized from the corresponding chiral iodoarenes through DMDO oxidations. Their oxidation states were determined by the 13C NMR chemical shifts of the ipso-carbon of the iodine atom, HRMS analysis, and elemental analyses. They were applied to the enantioselective hydroxylative dearomatization/[4+2]-dimerization cascade reactions of phenol derivatives to afford the desired products with up to 58%ee.

ChemInform Abstract: Enantioselective Oxidative Rearrangements with Chiral Hypervalent Iodine Reagents.

AbstractThis oxidative rearrangement of 1,1‐disubstituted alkenes provides simple access to enantioenriched α‐arylated ketones.

Enantioselective Oxidative Rearrangements with Chiral Hypervalent Iodine Reagents.

A stereoselective hypervalent iodine‐promoted oxidative rearrangement of 1,1‐disubstituted alkenes has been developed. This practically simple protocol provides access to enantioenriched α‐arylated ketones without the use of transition metals from readily accessible alkenes.