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Organoselenium compounds, due to their high structural diversity, special function, and biological activities, have drawn attention in synthetic chemistry. Herein, a novel example of chiral N,N′-di...

Transition states are of central importance in chemistry. While they are, by definition, transient species, it has been shown before that it is possible to “trap” transition states by applying stretching forces. We here demonstrate that the task of transforming a transition state into a minimum on the potential energy surface can be achieved by using hydrostatic pressure. We apply the computational eXtended Hydrostatic Compression Force Field (X- HCFF) approach to the educt of a [2,3]-sigmatropic rearrangement in both static and dynamic calculations and find that the five-membered cyclic transition state of this reaction becomes a minimum at pressures in the range between 100 and 150 GPa. Slow decompression leads to a 70:30 mix of the product and the educt of the sigmatropic rearrangement. Our findings are discussed in terms of geometric parameters and electronic rearrangements throughout the reaction. We speculate that the trapping of transition states by using pressure is generally possible if the transition state of a chemical reaction has a more condensed geometry than both the educt and the product, which paves the way for new ways of initiating chemical reactions.

An unprecedented [2,3]-sigmatropic rearrangement reaction of quaternary 2,3-allenylammonium ylides, generated in situ from tertiary 2,3-allenylamines and arynes, has been established. With 2-(trimethylsilyl)aryl triflates as aryne precursors, a range of tertiary 2,3-allenylamines bearing an electron-withdrawing group at the α-position smoothly participated in the aryne-mediated [2,3]-sigmatropic rearrangement at room temperature, delivering structurally diverse 2-vinylallyamines or 1-amino-1,3-dienes in moderate to excellent yields. The reaction proceeds in the absence of strong bases and transition metals, is compatible with moisture and air, and tolerates a wide variety of functional groups.

The rearrangement reaction of ammonium ylides furnishes valuable α,α-disubstituted amino esters. In this work, we describe the visible-light photolysis reaction of aryldiazoacetates in the presence of tertiary amines that react via a free ammonium ylide in a sigmatropic rearrangement reaction to provide amino esters in moderate to very good yields (33 examples, up to 97% yield).

A rapid and diastereoselective method was developed for the [2,3]-sigmatropic rearrangement of N-allyl ammonium ylides, affording products in up to 95% isolated yields and up to 97:3 dr; most of the desired products were formed within 1 minute. For the asymmetric reaction, a chiral auxiliary was introduced to the starting compound, affording the rearrangement product with high diastereoselectivities.

Dirhodium(II)-catalyzed oxonium ylide formation–[2,3]-sigmatropic rearrangement of 6-allyloxy-2-diazo-3-ketoesters possessing a C-6 substituent is described. The reaction of 6-alkyl- or 6-aryl-substituted 6-allyloxy-2-diazo-3-ketoesters with a catalytic amount of Rh2(S-PTTL)4 proceeded in a chemoselective and stereoselective manner to provide 6-substituted 2-allyl-3-oxotetrahydropyran-2-carboxylates in good yields and with high diastereoselectivities. To demonstrate the utility of this sequential reaction, we conducted the total synthesis of (+)-tanikolide, in which the construction of the δ-lactone skeleton was achieved by employing a 2-iodobenzamide-catalyzed oxidative cleavage of tetrahydropyran-2-methanol.

The first sequentially combined inorganic base promoted N-addition/[2,3]-sigmatropic rearrangement reaction of α-alkylidene pyrazolinones and propargyl sulfonium salts has been reported to construct homoallyl sulfur-containing pyrazolones with moderate to excellent yields. α-Alkylidene pyrazolinones function as N-nucleophilic agents distinguished from the reported C-addition reactions. Propargyl sulfonium salts were first involved in the [2,3]-sigmatropic rearrangement protocol differentiated from the well-established annulation reactions. The excellent regioselectivity, the broad scope of substrates, gram-scale synthesis and convenient transformation embody the synthetic superiority of this cascade process.

An oxa-[2,3] sigmatropic rearrangement involving arynes is reported featuring the umpolung of ketones, where the C═O bond polarity is reversed. The in situ-generated sulfur ylides from β-keto thioethers and arynes undergo efficient rearrangement allowing the facile and robust synthesis of functionalized enol ethers in high yields and excellent functional group compatibility. Preliminary mechanistic studies rule out the possibility of Pummerer-type rearrangement operating in this case.

The rearrangement of sulfur-containing aldehydes by using a sulfonium enamine intermediate as a formylcarbene mimetic is reported. This is an enantioselective, organocatalytic [2,3]-sigmatropic rearrangement enabling chiral cyclic sulfides bearing an α-quaternary chiral center to be prepared in high optical purity. The enantioselectivity is controlled with a cooperative organocatalyst pair consisting of a chiral amine and a chiral phosphoric acid (CPA). The synthetic versatility of this method is demonstrated by its rapid access to structurally diverse chiral spiro S-heterocycles.

A domino process to prepare chiral azabicycles with bridgehead quaternary stereogenic centers is reported., [2,3]-Sigmatropic rearrangement of ammonium ylides represents a fundamental reaction for stereoselective synthesis of nitrogenous compounds. However, its applicability is limited by the scarcity of efficient, catalytic, and mild methods for generating ammonium ylides. Here, we report silver-catalyzed domino generation/[2,3]-sigmatropic rearrangement of ammonium ylides, furnishing chiral azabicycles with bridgehead quaternary stereogenic centers in high enantiomeric purity (up to 99% ee). A combination of density functional theory calculations and experimental studies revealed that residual water in the reaction system is crucial for the mild reaction conditions by functioning as a proton shuttle to assist carbon-silver bond protonation and C2─H deprotonation to generate the ammonium ylide. This reaction has a broad application scope. Besides the diverse substituents, N-fused azabicycles of various ring sizes are also easily accessed. In addition to silver salts, this strategy has also been successfully implemented by using a stoichiometric amount of nonmetallic I2.

The chemo- and stereocontrolled functionalization of conjugated sulfinyl dienes in a cascade process that involves a Michael-type addition, isomerization of a double bond and a [2,3]-sigmatropic rearrangement is reported. Enantioenriched 1,4-diol and 1,4-aminoalcohol derivatives are obtained in a very straightforward manner. Further functionalization of these structures, including highly stereoselective epoxidation, dihydroxylation and the stereodivergent synthesis of several polyols in a controlled fashion is described, This research was supported by CTQ2016-77555-C2-2-R and MICINN (CTQ2009-07752). We also thank CM for additional support to MU and MEC for a fellowship to I.C

In the presence of 2-(trimethylsilyl)aryl triflates as aryne precursors under mild conditions, a range of tertiary propargylic amines bearing electron-withdrawing groups were converted to quaternary propargylic ammonium ylides followed by a [2,3]-sigmatropic rearrangement to afford structurally diverse amino-substituted allenes or conjugated dienes, depending on their structure, in moderate to good yields.

The [2,3]-sigmatropic rearrangement of allylic sulfoxides to allylic sulfenates is a reversible process, generally shifted toward the sulfoxide. In the presence of thiophiles, the sulfenate is trapped, and allylic alcohols are obtained under mild conditions. In most cases, a good transfer of stereochemical information through an ordered transition state is obtained. Furthermore, the ease of coupling this process with other versatile, stereocontrolled reactions has enhanced the usefulness of this protocol. This review aims to provide a comprehensive survey of this rearrangement and its application in the synthesis of natural and bioactive products., This research was supported by MINECO (Spain) (CTQ2013- 46459-C2-02-P, CTQ2016-77555-C2-2-R, CTQ2016-81797- REDC). We are grateful to Dr. Carmen de la Torre (IQOGCSIC) and Dr. Miguel Ángel Sierra (UCM) for encouragement and support

To date, more than 100 congeners of the akuammiline alkaloid family have been isolated. Their signature structural element is a methanoquinolizidine moiety, a cage-like scaffold structurally related to adamantane. The structural variations of the family members originate from oxidative processes that mostly trigger rearrangements of the methanoquinolizidine motif. The family of the akuammiline alkaloids is best represented by strictamine. It bears the least functionalized carbon skeleton of all family members without lacking the signature structural motifs. Herein, we report the formal synthesis of strictamine through a Stevens [2,3]-sigmatropic rearrangement as a key step and the synthetic pitfalls related with its synthesis.

A gold-catalyzed [2,3]-sigmatropic rearrangement reaction has been developed. The intermolecular rearrangement occurs between in situ generated donor-acceptor gold-carbenes and cinnamyl alcohols via tandem oxonium ylide formation. The desired rearranged product has been accomplished selectively over more conventional O-H insertion, cyclopropanation, cycloaddition, and C-H functionalization products under mild, open-air conditions. The scope of the work has been illustrated by synthesizing a new class of substrates that can be used for constructing complex molecular targets.

The scope of the [2,3]-sigmatropic rearrangement of propargylic sulfinates to allenic sulfones by silver catalysis was expanded. A series of new propargylic sulfinate esters was generated from a variety of aromatic and heteroaromatic sulfonyl chlorides and their rearrangement to allenic sulfones is reported. In addition, the synthesis of propargylic sulfinate esters containing electron-withdrawing benzenesulfonyl chlorides is reported.

An efficient protocol for [2,3]-sigmatropic rearrangement of allyl and propargyl thioethers is reported. The key sulfonium ylide intermediate is in situ formed via S-arylation of arynes. This transition metal-free method allows for ready access to a wide array of functionalized thioether derivatives in good to excellent yields.

A Cs2CO3-promoted Michael addition-[2,3]-sigmatropic rearrangement domino reaction between arenesulfonylindole and sulfur ylide has been developed. This reaction affords a facile method for the synthesis of 3-substituted indoles with a homoallyl sulfide moiety. In this domino sequence, two C−C bonds and one C−C bond cleavage were formed.

A new strategy has been established for the [2,3]-sigmatropic rearrangement of quaternary allylic ammonium ylides via in situ activation of tertiary allylic amines with arynes under mild conditions. Using 2-(trimethylsilyl)aryl triflates as aryne precursors, a range of tertiary allylic amines bearing electron-withdrawing groups underwent [2,3]-sigmatropic rearrangement to furnish structurally diverse homoallylic amines in moderate to good yields. The reaction enabled construction of quaternary stereocenters with excellent enantiopurity and functionalized cyclopropanes with extremely high diastereoselectivity.

Highly efficient catalytic asymmetric [2,3]-sigmatropic rearrangements of propargyl ammonium salts have been accomplished under mild reaction conditions. In the presence of the chiral isothiourea catalyst, a wide range of allenyl α-amino amide derivatives were obtained in generally good yields (up to 99%) with excellent enantioselectivities (up to 96% ee).

A base-induced dearomative [2,3] sigmatropic rearrangement of amino acid ester-derived ammonium salts followed by 1,4-elimination produced α-(ortho-vinylphenyl)amino acid esters. The reaction of azetidine-2-carboxylic acid-derived ammonium salt, (1S,2S,1′R)-3b, proceeded with a perfect N-to-C chirality transfer to afford α-(ortho-vinylphenyl)azetidine-2-carboxylic acid ester, (R)-5 (99% ee). On the other hand, the reaction of glycine-derived ammonium salt (R)-6a, which involves an efficient chirality transfer from a chiral benzylic carbon to an α-carbon of an ester carbonyl giving the optically active α-(ortho-vinylphenyl)glycine ester, (R)-8a (85% ee), was demonstrated. Although this dearomative [2,3] rearrangement followed by 1,4-elimination has limitations with regard to the structures of the substrates, our method provides unique access to substituted α-arylamino acid derivatives.

A new type of Rh2(OAc)4-catalyzed [2,3]-sigmatropic rearrangement of sulfur ylides is reported. A series of cyclopropenes were successfully employed for [2,3]-sigmatropic rearrangement by a reaction with either allylic or propargylic sulfides. Under the optimized conditions, the reaction afforded the products in moderate to excellent yields. In these transformations, the vinyl metal carbenes generated in situ from the cyclopropenes were effectively trapped by sulfides, resulting in the formation of corresponding products upon [2,3]-sigmatropic rearrangements.

An electrophilic trifluoromethylthiolation of allylic alcohols produces the corresponding allylic trifluoromethanesulfenates, which spontaneously rearrange into trifluoromethyl sulfoxides via a [2,3]-sigmatropic rearrangement. The reaction is straightforward and proceeds in good to high yields for the preparation of various allylic trifluoromethyl sulfoxides.

The research leading to these results (K.K.) has received funding from the ERC under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° 279850. A.D.S. thanks the Royal Society for a Wolfson Research Merit Award. The tetramisole-promoted catalytic enantioselective [2,3]-sigmatropic rearrangement of quaternary ammonium salts bearing a (Z)-3-fluoro-3-arylprop-2-ene group generates, after addition of benzylamine, a range of β-fluoro-β-aryl-α-aminopentenamides containing a stereogenic tertiary fluorine substituent. Cyclic and acyclic nitrogen substituents as well as various aromatic substituents are tolerated, giving the β-fluoro-β-aryl-α-aminopentenamide products in up to 76% yield, 96:4 dr, and 98:2 er. Postprint

The paper describes a convenient and efficient method for regioselective synthesis of phosphorylated α-hydroxyallenes using an atom economical [2,3]-sigmatropic rearrangement of intermediate propargyl phosphites or phosphinites. These can be readily prepared via reaction of protected alkynols with dimethyl chlorophosphite or chlorodiphenyl phosphine respectively in the presence of a base.

The trifluoromethylthio (SCF3) functional group has been of increasing importance in drug design and development as a consequence of its unique electronic properties and high stability coupled with its high lipophilicity. As a result, methods to introduce this highly electronegative functional group have attracted considerable attention in recent years. Although significant progress has been made in the introduction of SCF3 functionality into a variety of molecules, there remain significant challenges regarding the enantioselective synthesis of SCF3-containing compounds. Here, an asymmetric trifluoromethylthiolation that proceeds through the enantioselective [2,3]-sigmatropic rearrangement of a sulfonium ylide generated from a metal carbene and sulfide (Doyle-Kirmse reaction) has been developed using chiral Rh(II) and Cu(I) catalysts. This transformation features mild reaction conditions and excellent enantioselectivities (up to 98% yield and 98% e.e.), thus providing a unique, highly efficient and enantioselective method for the construction of C(sp3)-SCF3 bonds bearing chiral centres.

The sigmatropic rearrangement of propargylic sulfinates to allenic sulfones is catalyzed by the copper cation. The Pale Cu 1 -USY zeolite, as well as copper salts, lead to essentially quantitative yield of the corresponding allenic sulfones.

Novel [2,3]-sigmatropic rearrangements of oxonium ylides generated from α-oxo gold carbenes were discovered. An ­efficient synthetic method of 2,5-disubstituted dihydrofuran-3(2H)-ones via gold-catalyzed intermolecular oxidation of the allyl homopropargyl ethers with N-oxide was developed. And the synthetic utility of the current method has been proved by concise formal synthesis of (±)-kumausallene.

The Rh2(OAc)4-catalyzed oxonium ylide formation–[2,3]-sigmatropic rearrangement of a highly functionalized α-diazo-β-keto ester derived from d -glucose proceeded stereoselectively to give the corresponding tetrahydrofuran-3-one as a single diastereomer in high yield. This reaction was applied to the synthesis of 2-epi-cinatrin C1 dimethyl ester as a key step.

The total synthesis of (+)-tanikolide was accomplished by a traceless stereoinduction method using the key steps of a Rh(II)-catalyzed oxonium ylide formation–[2,3]-sigmatropic rearrangement and an N-heterocyclic carbene-catalyzed ring-expansion lactonization of tetrahydrofurfural. This synthetic route is applicable to the divergent synthesis of tanikolide analogues.

A facile synthesis of various allyl sulfonamides based on imidation of allyl sulfides with chloramine-T and subsequent [2,3]-sigmatropic rearrangement has been achieved without metal catalysts. The reaction completes smoothly within 10 min, providing excellent yields in environment friendly solvent of alcohol. Functional groups such as bromine, hydroxyl, protected amido and aldehyde are tolerant under this condition.

In this paper, Rh-2(OAc)(4)-catalyzed [2,3]-sigmatropic rearrangement of sulfur ylides derived from N-tosylhydrazones and sulfides is reported. A series of tosylhydrazones derived from aldehydes were successfully used for [2,3]-sigmatropic rearrangement by reaction with either allylic phenyl sulfides or propargyl phenyl sulfides. The reaction conditions were optimized and afforded the products in moderate to good yields. In addition, a novel and convenient approach for the synthesis of cyclobutenones and cyclopropanes has been developed through direct oxidation of the rearrangement products. (C) 2012 Elsevier Ltd. All rights reserved.

The tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor rhodium carbenoids and chiral allyl alcohols is a convergent C-C bond forming process, which generates two vicinal stereogenic centers. Any of the four possible stereoisomers can be selectively synthesized by appropriate combination of the chiral catalyst Rh(2)(DOSP)(4) and the chiral alcohol.

α-Amino allenephosphonates were easily prepared in two steps from protected amines, propargyl alcohols, and chlorophosphites. First, ynamides were synthesized from unprotected 1-bromopropargyl alcohols using a copper(II) catalyzed coupling reaction. In the second step, the previously prepared ynamides were transformed directly to allenes through a [2,3]-sigmatropic rearrangement of propargyl phosphites. This efficient method led to the formation of a series of α-amino allenephosphonates with diverse substituents on the amine, the phosphonate, and the allene moieties.

CrCl2/Mn-mediated transformation of various dibromofluoromethylcarbinyl esters including carboxylates, carbonates and carbamates provided 1-fluoro-1-alkenyl esters via [2,3]-sigmatropic rearrangement of ester group. Reaction proceeded by using CrCl2/Mn system under mild conditions (in THF at room temperature) to give 1-fluoro-1-alkenyl esters in good yield with an excellent Z selective manner. 1-Fluoro-1-alkenyl ester thus obtained acts as a double acyl donor in the reaction with necleophiles such as amine, thiol, alcohol as well as bifunctional necleophiles such as ethylene diamine derivative.

The highly diastereoselective base-promoted intramolecular cyclization of a variety of enantiopure sulfinyl dienyl amines provides novel sulfinyl tetrahydropyridines that are readily converted to 3-hydroxy tetrahydropyridines via sigmatropic rearrangement. The influence of N- and C- substituents on the process has been studied. Procedures to shorten the sequence such as the tandem cyclization followed by [2,3]-sigmatropic rearrangement, as well as cyclization of the free amine, under Boc- or ArSO- deprotection conditions have been examined. Good to excellent levels of selectivity are generally observed for the reported transformations (dr: 75/25 to >98/2). A novel protocol to access substituted amino dienyl sulfoxides is also reported.

The development of an efficient oxidative [2,3]-sigmatropic rearrangement of allylic hydrazides, via singlet N-nitrene intermediates, is reported. The requisite allylic hydrazide precursors are readily prepared and undergo smooth sigmatropic rearrangement upon exposure to iodosobenzene. The products of this novel transformation are shown to be useful precursors to a variety of compounds.

International audience; A new efficient access to functionalized CF3-substituted and nitrogen or sulfur-containing heterocycles has been developed directly from diazocompounds CF3C(N2)Z (Z=CO2Me, P(O)(OEt)2). The method is based on the direct selective synthesis of doubly unsaturated substrates followed by metal-mediated carbocylization. The first step has been performed by Cu(II)-catalyzed [2,3]-sigmatropic rearrangement of propargyl- or/and allyl-containing sulfur and nitrogen ylides leading to fluorinated enynes, diolefins, and especially allenynes derivatives. The second step involves their carbocyclization via ring closing metathesis and Pauson-Khand reaction.

The first investigation on catalytic asymmetric [2, 3]-sigmatropic rearrangement of sulfur ylides generated from carbenoids and allenic phenyl sulfide was carried out. Up to 55% ee value was obtained.

This paper reviews the most recent development of [2,3]-sigmatropic rearrangement of sulfur ylide generated from the reaction of sulfide with metal carbene. The metal carbene was formed from decomposition of diazo compounds catalyzed by transition metal complexes such as Cu(I) and Rh(II).

The rhodium-catalyzed reaction of racemic allyl alcohols with methyl phenyldiazoacetate or methyl styryldiazoacetate results in a two-step process, an initial oxonium ylide formation followed by a [2,3]-sigmatropic rearrangement. This process competes favorably with the more conventional O-H insertion chemistry as long as donor/acceptor carbenoids and highly substituted allyl alcohols are used as substrates. When the reactions are catalyzed by Rh(2)(S-DOSP)(4), tertiary alpha-hydroxycarboxylate derivatives with two adjacent quaternary centers are produced with high enantioselectivity (85-98% ee).

The [2,3]sigmatropic rearrangement of allylic ammonium ylides generated by the reaction of N,N-dimethyl-1-alkyl-2-methylallylamines derived from terpene alcohols with diazo compounds in the presenc...

A number of thieno[2,3-b]thiophenes have been successfully synthesized in a 50–55% yield by m-chloroperoxybenzoic acid–mediated tandem cyclization involving [2, 3] and [3, 3] sigmatropic rearrangements and an intramolecular Michael addition.