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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

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.

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.

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 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.

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 first asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines has been realized by quaternization of the amines with an enantiomerically pure diazaborolidine and subsequent treatment with Et3N. The resultant homoallylic amines were obtained in good yields and excellent ee's. The observed diastereo- and enantioselectivities were rationalized by invoking a kinetically controlled process, and support for this model was obtained from an NMR spectroscopic investigation of the chiral Lewis acid-substrate complex. The structure of the Lewis acid-product complex was established by X-ray crystallographic analysis and supported the proposed mechanism.

The first examples of sigmatropic rearrangements of ene-endo-spirocyclic, tetrahydropyridine-derived ammonium ylids are reported. Thus, spiro[6.7]-ylids rearrange primarily by a [2,3]-pathway, whereas the analogous [6.6]-ylids rearrange by [1,2]- and [2,3]-mechanisms in roughly equal proportions. This method serves as a rapid entry to the core of a range of alkaloids bearing a pyrrolo[1,2-a]azepine or octahydroindolizidine nucleus.

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).

The reaction of a series of ketones with dimsylsodium in dimethyl sulfoxide resulting in the formation of γ-unsaturated thiols was studied experimentally. [2,3]-Sigmatropic rearrangements of β-unsaturated sulfinyl carbanions are involved at the key step of those transformations. DFT computations at the B3LYP/6-31+G* level indicated that such rearrangements, as well as some typical [2,3]-sigmatropic rearrangements, e.g., thermal rearrangements of allyl sulfoxides and Wittig rearrangements of sulfur ylides and lithiated allyloxy methyl anions, are concerted and moderately synchronous processes. Negative (diatropic) nucleus-independent chemical shifts (NICS) and high diamagnetic susceptibility exaltations indicate that the transition structures of these [2,3]-sigmatropic migrations are aromatic.

The asymmetric Diels-Alder reactions of (R)-1-(p-tolylsulfinyl)-1,3-bu- tadienes (3a-c) with N-methylmaleimide (NMM) have been explored. The cycloadditions are stereospecific: only one endo adduct is formed, the π-facial diastereoselectivity being controlled by the sulfoxide both in thermal and catalytic conditions. The in situ cycloaddition/sulfoxide sulfenate [2,3]-sigmatropic rearrangement starting from chiral (3a-c) in the presence of an excess of NMM, which acts as thiophilic agent, provides a convenient one-step access to enantiomerically pure and all- cis functionalized cyclohexenols (-)-5a-c

Several β-sulfoxy-substituted acetylenic carbinols were prepared by the addition of thiyl radicals and oxygen to conjugated enynes. The products obtained are derived from thiyl radical attack at the olefinic bond to generate a propargylic radical. Capture of this radical by oxygen followed by hydrogen transfer from thiophenol gives a hydroperoxide intermediate, which undergoes oxygen transfer by both intra- and intermolecular pathways. The resultant β-phenylsulfinyl propargylic alcohols proved to be versatile intermediates for the preparation of several different classes of compounds. The [2,3]-sigmatropic sulfinate to sulfoxide rearrangement was found to give 1,4-bis(phenylsulfonyl)1,3-butadienes, α,β-unsaturated phenylsulfoxy ketones, and β-phenylsulfonyl α-allenic sulfoxides

Addition of germanium dichloride dioxane complex to α,β-unsaturated acetals gives β-dichloroalkoxygermane enol ethers via a net [2,3]-sigmatropic rearrangement

A thioxanone-based [2,3]-sigmatropic rearrangement strategy which delivers Cβ-chiral pent-4-enoic acids with excellent Cβ-induction is reported

An asymmetric Lewis acid-mediated [2,3]-sigmatropic rearrangement of allylic amines has been developed, affording the corresponding homoallylic amines in good yield and excellent enantioselectivities. The rearrangement proceeds by complexation of the chiral Lewis acid to the amine followed by deprotonation and rearrangement.

Attempts to achieve configurational inversion of tertiary allylic alcohols by the ''classical'' approach comprising S/sub N/2-type displacement of suitable derivatives are invariably thwarted by the almost exclusive formation of allylic rearrangement and/or elimination products, nor does the diethyl azodicarboxylate-triphenylphosphine system work with tertiary substrates. Sparse reports suggest that the allyl sulfoxide-sulfenate rearrangement could be advantageously exploited to this end, although in one direction only. Illustrations on this concern are provided by the conversion of prostaglandin (13Z,15R)-PGE/sub 1/ into the 13E,15S analogue and a new route to the dihydroxyacetone side chain from a 17..cap alpha..-ethynyl-17..beta..-hydroxy steroid. In this paper it's reported (a) that an effective ''one-pot'' epimerization procedure of 17..cap alpha..-vinyl-17..beta..-hydroxy steroids to the rather inaccessible 17-epimers can be assembled by the use of the above rearrangement and (b) some stereochemical observations on this process.