Thiirenium Ions Research Articles

Synthesis of Aryl Thioalkynes Enabled by Electrophilic Sulfenylation of Alkynes and the Following Elimination.

An unexpected deprotonative process of thiirenium ions is presented, which provides a new synthesis of aryl thioalkynes directly from terminal alkynes via the electrophilic activation of the carbon-carbon triple bonds. The conditions are well compatible with various functional-group-substituted aryl alkynes. The direct elimination from the thiirenium ion intermediate, or its tautomer, benzyl vinyl carbocation, is supported by control experiments and labeling reaction.

Generation and reactions of thiirenium ions by the Cation Pool method

Generation and reactions of thiirenium ions by the Cation Pool method

Nucleophilic reactions at the ring carbons of thiiranium and thiirenium ions. An experimental and theoretical comparison of the SN2 and SN2-Vin mechanisms

Generally, the bimolecular nucleophilic substitution at the saturated carbon (SN2) and the mechanistically similar substitution at the vinyl carbon (SN2-Vin) cannot be quantitatively compared, because of the many interfering steric and electronic factors. The cis and trans rearrangements of trans c-2,t-3-di-tert-butyl-r-1-methylthiiranium ion 5a into thietanium ions 6a and 6b and that of 2,3-di-tert-butyl-1-methylthiirenium ion 7 into thietium ion 8 can be be compared both experimentally and computationally. They occur with intramolecular SN2 and SN2-Vin mechanisms respectively and are both almost exclusively governed by the nucleofugality of the sulfonium leaving group.

X-ray structures and anionotropic rearrangements of Di-tert-butyl-substituted thiiranium and thiirenium ions. A structure-reactivity relationship

The X-ray structures of c-2,t-3-di-tert-butyl-r-1-methylthiiranium 8 BF(4)(-), t-2,t-3-di-tert-butyl-r-1-methylthiiranium ion 10 BF(4)(-), and 2,3-di-tert-butyl-1-methylthiirenium 11 BF(4)(-) have been determined. The DeltaG()(298) values for the rearrangements from the cis and the trans tert-butyl groups of 8 SbCl(6)(-) to thietanium ion (two intramolecular S(N)2 displacements) and for the rearrangement of 11 SbCl(6)(-) to thietium ion (an intramolecular S(N)2-Vin displacement) are linearly correlated with the strengths of the C-S breaking bonds, suggesting that the two mechanisms are, in the absence of steric hindrance, uniquely governed by the nucleofugality of the sulfonium leaving group.

Are the Approach Directions of σ and π Nucleophiles to the Sulfur Atom of Thiiranium and Thiirenium Ions Different?

A collinear approach to the sulfur atom of thiiranium and thiirenium ions (see scheme) is predicted by theoretical calculations for both σ and π nucleophiles.

Different approaching directions of sigma and pi nucleophiles to the sulfur atom of thiiranium and thiirenium ions

Different approaching directions of sigma and pi nucleophiles to the sulfur atom of thiiranium and thiirenium ions

Nucleophilic Reactions at the Sulfur of Thiiranium and Thiirenium Ions. New Insight in the Electrophilic Additions to Alkenes and Alkynes. Evidence for an Episulfurane Intermediate

The thiiranium hexachloroantimonates 1a, 3, and 5a−c and the thiirenium hexachloroantimonates 6a−c and 7a with exocyclic S-R substituent (R = Me, Et, i-Pr) react at sulfur with dialkyl disulfides R‘ ‘SSR‘ ‘ (R‘ ‘ = Me, Et and R‘ ‘ ≠ R) in CD2Cl2 at 25 °C to give S-R‘ ‘ substituted ions. The reaction rates are affected by the steric hindrance of the substituents at sulfur and at ring carbons. t-2,t-3-Di-tert-butyl-r-1-methylthiiranium hexachloroantimonate (2) does not react, and the t-2-tert-butyl-c-3-phenyl-r-1-methylthiiranium (5a) reacts about 100 times faster than the c-2,t-3-di-tert-butyl-r-1-methylthiiranium ion (1a). The analysis of the kinetic data suggests that the sulfonium sulfur undergoes attack by the disulfide in the ring plane from a direction that is parallel to the C−C ring bond. This is also the direction which ensures the maximum overlap with the LUMO of thiiranium or thiirenium ions (determined at the RHF/3-21G*//RHF/3-21G* level). The combined consideration of the approach modality and...

Sulfur Electrophiles as Mechanistic Probe. New Insight in the Electrophilic Additions

Thiiranium and thiirenium ions are stable intermediates that have been isolated and fully characterized. Structures of tert-butyl substituted thiiranium and thiirenium ions have been determined by room temperature single X-ray diffraction. In addition ab initio calculations at RHF/3-21G*//RHF/3-21G* level have been performed. Along with the definition of the structural parameters of these ions, the mechanism of their reactions with a series of sulfides has been investigated. We focus in this paper on the nucleophilic attack to sulfonium sulfur. The kinetic data, the molecular geometries, the shapes and energies of the frontier molecular orbitals suggest a mechanism in which the nucleophile approaches the sulfur in the ring plane along a direction parallel to the C-C ring bond. This result implies the intermediacy of a episulfuranic species.

ChemInform Abstract: Thiiranium and Thiirenium Ions. From Reaction Intermediates to Building Blocks in Organic Synthesis

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Thiiranium and Thiirenium Ions Chemistry and Stereochemistry

Abstract The role of thiiranium and thiirenium ions in the electrophilic additions to alkenes and alkynes and the corresponding inverse reactions, are revisited also in the light of the recently reported rearrangements on some of these cations. The occurrence of SN2-Vin mechanism is discussed on the basis of the available experimental evidence and of quanto mechanical computation. Preliminary results on the reactivity of some stable thiiranium ions as a function of substitution pattern and on the enantioselective bifunctionalization of alkene via an optically active thiiranium ion are also reported.

Reaction of 4′-nitrobenzenesulfenanilide (NBSA) with Lewis acids. A study of its application in sulfenocyclization of alkenes and alkynes

Phenylsulfenocyclization of a number of alkenes and alkynes possessing internal hydroxyl, carboxyl or vinyl functionality has been investigated with NBSA. Thioetherification of 4-penten-1-ol 4 as well as thiolactonization of 4-penten-1-oic acid 7 and, to a modest extent, 4-pentyn-1-oic acid 8 can be successfully achieved with NBSA in the presence of boron trifluoride. On the other hand, under analogous conditions 3-buten-1-ol 3 and 3-buten-1-oic acid 6 fail to undergo thiocyclization and give instead oxa- and/or aza-sulfenylation 1,2-adducts. Similar failure is observed with 4-pentyn-1-ol 5, in which case diphenyl disulfide and 4-nitroaniline are the exclusive products. Hexa-1,5-diene 9, to some extent, affords a cyclized arylaminosulfide, i.e. 23, ascribable to formal loss of a methylene unit from the initial (phenylthiomethyl)- cyclopentyl cation 24. The reaction products are discussed in terms of intermediate thiiranium and thiirenium ions whose decomposition mode is strictly dependent upon their structural features. Novel evidence is also presented that aluminium chloride and bromide can promote reaction of NBSA with alkenes and alkynes to afford chloro- and bromo-sulfenylation adducts in varying yields.

Thiiranium and Thiirenium Ions Chemistry and Stereochemistry

Abstract The role of thiiranium and thiirenium ions in the electrophilic additions to alkenes and alkynes and the corresponding inverse reactions, are revisited also in the light of the recently reported rearrangements on some of these cations. The occurrence of SN2-Vin mechanism is discussed on the basis of the available experimental evidence and of quanto mechanical computation. Preliminary results on the reactivity of some stable thiiranium ions as a function of substitution pattern and on the enantioselective bifunctionalization of alkene via an optically active thiiranium ion are also reported.

Electrophilic addition of 4′-nitrobenzenesulphenanilide to alkynes in acetic acid. A synthesis of β-acetoxyvinyl sulphides

4′-Nitrobenzenesulphenanilide reacts at room temperature with simple alkyl- and aryl-alkynes in acetic acid in the presence of boron trifluoride–diethyl ether to afford products of acetoxysulphenylation in moderate to good yields. The addition products are generally produced with trans-stereospecificity and in a regioselective fashion (Markovnikov orientation). The findings are consistent with a mechanism involving intermediary of thiirenium ions which would result from alkyne attack at the sulphur atom of the anilide complexed with boron trifluoride.

An attempt to detect thiirenium ions in the gas phase

CnH2n–1S+ ions (n3–5,7,11) were generated in the gas phase from several CH3SCR1= CR2X precursors (R1,R2= H, alkyl; X = Cl, Br)via electron-impact-induced X˙ loss. Their reactions, unimolecular and collision induced, were studied by ion kinetic energy spectrometry. The major fragementations are identified and the thermochemistry considered. Of particualr interest were unimolecular alkene elimination reactions, observed for n= 3–5, which lead to product ions of composition R1(R2)CS+. C4H7S+ ions undergo elimination of C2H4 and C3H6 to give C2H3S+ and HCS+, respectively. Metastable peak shape analysis, analysis of model ions, and deuterium labelling experiments show that the two reactions occur via two different mechanisms. A general scheme is proposed for unimolecular decomposition of CnH2n–1S+ ions. Thiirenium ions could not be detected nor need be invoked as intermediates in the extensive rearrangements that precede some of the major reactions.

ChemInform Abstract: THIIRANIUM AND THIIRENIUM IONS

Chemischer InformationsdienstVolume 9, Issue 19 Reviews ChemInform Abstract: THIIRANIUM AND THIIRENIUM IONS G. H. SCHMID, G. H. SCHMIDSearch for more papers by this author G. H. SCHMID, G. H. SCHMIDSearch for more papers by this author First published: May 9, 1978 https://doi.org/10.1002/chin.197819334AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume9, Issue19May 9, 1978 RelatedInformation

Formation and reactivity of thiirenium ions

Evidence is reported that thiirenium ions are involved as intermediates in both the addition of benzenesulphenyl chloride to diarylacetylenes and in unimocular substitution reactions of β-phenylthiovinyl sulphonates. The thiirenium ion generated from 1,2-diphenyl-2-phenylthiovinyl 2,4,6-trinitrobenzenesulphonate undergoes nucleophilic attack by chloride ion both at the carbon atoms to give 1,2-diphenyl-2-phenylthiovinyl chloride and at the sulphur atom to give diphenylacetylene and benzenesulphonyl chloride which can be trapped by added scavengers.

Reactivity of vinyl sulphonic esters. Part XIII. Pronounced anchimeric assistance in the solvolysis of dialkyl-β-alkyl(or aryl)thiovinyl sulphonates

trans-1,2-Dimethyl-2-methylthiovinyl 2,4,6-trinitrobenzenesulphonate reacts ca. 4 × 104 times faster than tri-methylvinyl 2,4,6-trinitrobenzenesulphonate in 9 : 1 nitromethane–methanol at 25°. These and other kinetic data on the solvolysis of a number of 1,2-dimethyl- and 1,2-di-n-propyl-β-alkyl(or aryl)thiovinyl sulphonates are taken as evidence of effective anchimeric assistance by the β-sulphur atom and of the intermediacy of thiirenium ions.