Episulfonium ions: myth and reality

Smit, V. A.; Zefirov, N. S.; Bodrikov, I. V.; Krimer, M. Z.

doi:10.1021/ar50140a003

Cited by 186 publications

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References 35 publications

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“…On examination of On the basis of these data and the plethora of results previously published (5,6,15), a mechanism involving at least one intermkdiate and two transition states is required. Although many variations on the following scenarios are conceptually possible, two mechanisms have received the most attention (see Scheme 1).…”

Section: Resultsmentioning

confidence: 94%

“…In path b the formation of an episulphurane intermediate may occur in such a way that little or no charge develops on sulphur in the transition state, despite the obvious redox nature of the reaction. Although conclusive evidence is lacking, at this time, as to which path most correctly corresponds to the actual reaction hypersurface, it is clear that given the dissociation of the sul~hur-chlorine bond in an episulphurane-like intermediate one arrives at the same series of thiiranium ion-pairs, which serve to define the probable product determining transition state structures (5,6).…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, this system is of interest since it allows one to ascertain the regiochemistry of the reaction. The importance ofthis latter point has been discussed in a number of recent reviews (5,6).…”

Section: 0mentioning

confidence: 99%

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Addition of arenesulphenyl chlorides to 2-methylenebicyclo[2.2.1]hept-5-ene: effect of increasing electron demand upon the rate and product determining transition states

Garratt¹,

Beaulieu²,

Morisset³

1980

Can. J. Chem.

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The rates and products of addition of a series of s~xteen arenesulphenyl chlorides to 2-methylenebicyclo[2.2. Ilhept-Sene, 7, and the E , Z isomeric 2-ethylidenebicyclo[2.2. Ilhept-5-enes, 8 and 9, have been determined in methylene chloride solution. The major species from attack on 7 is always endo-3-arylthio-I-chlorornethyltricyclo[2.2. 1.02~6]heptane, the product of exo attack upon the endocyclic double bond with homoallylic participation of the exacyclic n system. N o evidence was found for initial electrophilic attack upon the exocyclic double bond. Chem. 58, 1021Chem. 58, (1980 In two previous articles (1,2) we have discussed intermediates of type 3 and 4 instead of the comthe effect of increasing electron demand (3) upon monly accepted sulphonium ions 5 and 6 (4). the product determining transition state in the In regard to this latter point, we observed a reaction of arenesulphenyl chlorides with car-stabilizing interaction only in the case of 2,4-bon-carbon double bonds and single bonds using dinitrobenzenesulphenyl chloride, presumably as a respectively bicyclo[2.2.l]hepta-2.5-diene, 1, and result of the dual electron withdrawal of both nitro tetracycl0[3.2.0.0~.~.0~.~]heptane, 2, as substrates. groups, since in the presence of more electron donating substituents in the para position one observes only the electron withdrawing properties of the ortho nitro group.The aim of these studies was two-fold. Firstly, we desired to ascertain the effect of varying the elec-

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

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Addition of arenesulphenyl chlorides to 2-methylenebicyclo[2.2.1]hept-5-ene: effect of increasing electron demand upon the rate and product determining transition states

Garratt¹,

Beaulieu²,

Morisset³

1980

Can. J. Chem.

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“…Thiiranium ion intermediates have been generated by reactions of disulfides with alkenes in the presence of oxidants such as Pb(OAc) 4 [1][2][3][4], Mn(OAc) 3 [2][3][4], Fe(OAc) 3 [2][3][4] or Cu(OAc) 2 [5], by reactions of β-thiohalides with AgY [6] and by reactions of thiiranes with RY [6]. The intermediates which have soft counterions such as BF 4 − , PF 6 − , SbF 6 − , SbCl 5 − , FSO 3 − and CF 3 CO 2 − behave like carbenium ions [1] of a weakly bridged strong electrophile, undergoing a rapid ring-opening by the outer nucleophile at low temperature (−20-0 o C) to give the observed predominant Markovnikov regioselectivity; in some cases, the skeletal rearrangement or stereoconversion of the thiiranium ions has been observed.…”

Section: Introductionmentioning

confidence: 99%

“…The intermediates which have soft counterions such as BF 4 − , PF 6 − , SbF 6 − , SbCl 5 − , FSO 3 − and CF 3 CO 2 − behave like carbenium ions [1] of a weakly bridged strong electrophile, undergoing a rapid ring-opening by the outer nucleophile at low temperature (−20-0 o C) to give the observed predominant Markovnikov regioselectivity; in some cases, the skeletal rearrangement or stereoconversion of the thiiranium ions has been observed. We may infer that the reactions of RSCl with alkenes would generate not a σ-sulfurane but a strongly bridged thiiranium ion pairing tightly with hard Cl − [1], and thus the ring-opening by the pairing Cl − leads to the anti-Markovnikov regioselectivity without undergoing the stereoconversion and skeletal rearrangement. In this work, reactions of dimethyl disulfide with 2-alkyl and 2,2-dialkylalkenes in AcOH in the presence of Pd(OAc) 2 lead to the anti-Markovnikov and Markovnikov regioselectivity products, respectively, for the addition to the alkenes.…”

Section: Introductionmentioning

confidence: 99%

Novel Behavior of Thiiranium Radical Cation Intermediates. Reactions of Dimethyl Disulfide with Alkenes in the Presence of Pd(OAc)2

2000

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Reaction of dimethyl disulfide (1) with cyclohexene (2a) in AcOH in the presence of Pd(OAc) 2 yields trans-1-acetoxy-2-methylcyclohexane (3a). The equivalent reactions with hex-1-ene (2b) and 2-methylpent-1-ene (2c) or 1-methylcyclohex-1-ene (2d) preferentially give anti-Markovnikov and Markovnikov adducts 4 and 3, respectively, by acetoxymethylthiolation of the alkene. The Markovnikov regioselectivity 3b/4b for the reaction with 2b is higher than that for the reaction using AgOAc instead of Pd(OAc) 2, which proceeds via a thiiranium ion. Addition of a polar solvent (MeCN or MeNO 2 ) to the reactions with 2b or 2c using Pd(OAc) 2 abnormally decreases the Markovnikov regioselectivity. The total yield of 3 and 4 increases with an increased concentration of AcOH. Compounds 3 and 4 are also formed and the reactions in MeCN or MeNO 2 not containing AcOH. A solution of Pd(OAc) 2 in 1 exhibits λ max 380 nm (log ε 3.6) assigned to the absorption of a relatively stable sulfonium salt. These indicate that the reactions using Pd(OAc) 2 proceed by S N 2 ringopening of a new type of thiiranium radical cations paired with − OAc via the sulfonium salts. The insensitivity of the 3/4 ratios to the reaction time at 25-60°C in the reactions with 2c-d shows the ring-opening to be controlled kinetically, but the increased ratio with reaction time at 116°C in the reaction with 2b suggests that the ring-opening is thermodynamically governed. The reaction product with 2d also undergoes a skeletal rearrangement to a thietanium radical cation to give 1-acetoxymethyl-2-methylthiocyclohexane.

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2,4-Dinitrobenzenesulfenyl Chloride

McKinney¹

2001

Encyclopedia of Reagents for Organic Synthesis

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Episulfonium ions: myth and reality

Cited by 186 publications

References 35 publications

Addition of arenesulphenyl chlorides to 2-methylenebicyclo[2.2.1]hept-5-ene: effect of increasing electron demand upon the rate and product determining transition states

Addition of arenesulphenyl chlorides to 2-methylenebicyclo[2.2.1]hept-5-ene: effect of increasing electron demand upon the rate and product determining transition states

Novel Behavior of Thiiranium Radical Cation Intermediates. Reactions of Dimethyl Disulfide with Alkenes in the Presence of Pd(OAc)2

2,4-Dinitrobenzenesulfenyl Chloride

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