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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...

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 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.

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.

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.

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 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.

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.

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.

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).

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.

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., This research was supported by MINECO (CTQ2013-46459- C2-2-P) and (CTQ2009-07752) cofunded by FEDER. We also thank CSIC for a contract to RHB (201080E101) and CSIC and Fondo Social Europeo for a JAE-doc contract to CS. LI thanks Comunidad de Madrid (Spain) for support (BIPEDD-2: S2010-BMD-2457). We are grateful to Dr. Carmen de la Torre (IQOG-CSIC) and Dr. Miguel Ángel Sierra (UCM) for encouragement and support.

The applied catalyst (zeolite Ag-USY) can be recycled several times and therefore this reaction becomes “greener”.

The Rh(I)-catalyzed Pauson–Khand reaction of allenynes afforded the bicyclo[6.3.0]undecadienones as well as their benzo and furo derivatives. In addition, a novel [RhCl(CO)2]2-catalyzed [2,3]-sigmatropic rearrangement of the sulfinic ester species of propargyl alcohols was developed.

A ring-contractive and highly diastereoselective [2,3]-sigmatropic rearrangement occurs when N-methyl-1,2,3,6-tetrahydropyridine is treated with sub-stoichiometric amounts of copper or rhodium salts, in the presence of ethyl diazoacetate, giving ethyl cis-N-methyl-3-ethenyl proline (4).

Catalytic asymmetric [2,3] sigmatropic rearrangement of sulfur ylides generated from aryldiazoacetates and propargyl sulfides with a number of chiral Rh(II) and Cu(I) catalysts have been investigated and moderately high enantioselectivities (up to 81% ee) have been achieved.

The tandem sulfonium ylide formation-[2,3]-sigmatropic rearrangement reaction of chiral non-racemic secondary allylic sulfides, (E)-9 and (Z)-10, is found to proceed with high diastereocontrol. The C-5 stereocenter bearing the sulfide group is essential for high diastereoselectivity in the reaction. Transition state conformers are proposed to explain the high diastereoselectivity in the formation of the diastereomeric products, 18a and 18b. The method is applied to the synthesis of (R)-4-(4-chlorophenyl)-2-butyrolactone. Modest enantioselectivity (63% ee) was achieved and this is attributed to partial racemization during the formation of the secondary allylic sulfide 22.

A number of 3-(4′-aryloxybut-2′-ynyl)thio-5,5-dimethyl cyclohex-2-enones are synthesized in 80–90% yield by phase transfer catalyzed reaction of 5,5-dimethyl-3-merca-ptocyclohex-2-enone with a number of 1-aryloxy-4-chlorobut-2-ynes. The sulfides are oxidized with 1 equiv. of m -chloroperoxybenzoic acid and the resulting sulfoxides are then stirred at r.t. for 6–8 h to give 2-aryloxymethyl-3-( m -chlorobenzoyloxy)-6,6-dimethyl-5,6,7-trihydro benzo( b )thiophene-4-ones in 70–80% yield.

A convenient protocol is developed for the denitrogenative [2,3] sigmatropic rearrangement of triazoles with allyl sulfides and benzylphenyl sulfide.

This paper describes the first examples of catalyst-dependent asymmetric induction in the periselective [2,3]-sigmatropic rearrangement of propargylic oxonium ylides generated by catalytic diazo decomposition. Catalysis of α-diazo-s-keto esters 4a—g using dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] in toluene has led to the virtually exclusive formation of benzofuran-3-ones bearing an allenic group with up to 79% ee.

Trimethylsilyldiazomethane reacts with allylic sulfides in the presence of catalytic quantities of Rh2(OAc)4 (1 mol%) to give homoallylic sulfides in good yields and with high diastereoselectivity.

Trimethylsilyldiazomethane is compared with ethyl diazoacetate for the rhodium, copper, and cobalt catalyzed formation and [2,3] rearrangement of allylsulfonium ylides. At room temperature, the reaction can be carried out using the allyl sulfide as the limiting reagent by slow addition of 3 equivalents of the diazo compound. Slightly better yields were obtained with trimethylsilyldiazomethane than with ethyl diazoacetate.

Oxonium ylide [2,3] sigmatropic rearrangement of trans-divinyl ethylene oxide is observed upon its exposure to ethyl or t-butyl diazoacetate in the presence of either Rh(II) or Cu(II) catalysts to produce cis-6-vinyl-3,6-dihydropyran-2-carboxylates.

The formation of 13-membered ring oxonium ylides and their subsequent stereocontrolled [2,3]-sigmatropic rearrangement to 10-membered ring lactones occurs in catalyst dependent competition with macrocylic cyclopropanation.

Several new chiral rhodium(II) catalysts have been synthesised for evaluation as catalysts in asymmetric oxonium ylide-[2,3] sigmatropic rearrangement of diazocarbonyl substrates; a catalyst derived from (S)-tert-leucine afforded a chiral benzofuranone derivative with an ee of 60 %.

Allyl aryl sulfides and diazoacetic acid esters react in the presence of optically active Co(III)-salen complex (4) with good enantioselectivity, to give the [2,3]sigmatropic rearrangement products, 2-arylthio-3-aryl-4-pentenoic acid esters, via the corresponding S-ylides.

Chemical building blocks: ?-Sulfenylated imines containing a quaternary center, an ubiquitous subunit and excellent building block, were achieved by rhodium-catalyzed denitrogenative [2,3] sigmatropic rearrangements of N-sulfonyl-1,2,3-triazoles with allylaryl(alkyl) sulfides. Coupling of this methodology with a copper-catalyzed cycloaddition reaction provides a platform for the direct regioselective functionalization of alkynes (see scheme; TC=thiophenecarboxylate; Ts=p-toluenesulfonyl). � 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reaction of carbenoids with propargylic alcohols results in tandem oxonium ylide formation/[2,3]-sigmatropic rearrangement to yield allenes with high enantioselectivity.

Two vicinal stereogenic centers are generated in the title reaction with excellent enantioselectivity.

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.

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.