Looking for a Paradigm for the Reactivity of Phenonium Ions

Protti, Stefano; Dondi, Daniele; Mella, Mariella; Fagnoni, Maurizio; Albini, Angelo

doi:10.1002/ejoc.201100305

Cited by 25 publications

(23 citation statements)

References 40 publications

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“…It was also observed that an aryl group migration is preferable over that of a vinyl group, which might be from the stabilization of azidonium intermediate II by a phenonium ion. Therefore, the overall observed migratory aptitude is: aryl group > vinyl group 37b,37c…”

Section: Resultsmentioning

confidence: 99%

Copper‐Catalyzed Direct Transformation of Secondary Allylic and Benzylic Alcohols into Azides and Amides: An Efficient Utility of Azide as a Nitrogen Source

2015

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A mild and convenient method for the synthesis of amides has been explored by using secondary alcohols, Cu(ClO4)2·6H2O as a catalyst, and trimethylsilyl azide (TMSN3) as a nitrogen source in the presence of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) at ambient temperature. This method has been successfully adapted to the preparation of azides directly from their corresponding alcohols and offers excellent chemoselectivity in the formation of ω‐halo azides and the azidation of allylic alcohols in the presence of a benzyl alcohol moiety. In addition, this strategy provides an opportunity to synthesize azides that can serve as precursors to β‐amino acids.

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Section: Resultsmentioning

confidence: 99%

Copper‐Catalyzed Direct Transformation of Secondary Allylic and Benzylic Alcohols into Azides and Amides: An Efficient Utility of Azide as a Nitrogen Source

2015

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“…Bridging phenonium ions were at one time the subject of intense interest in studies to characterize internal [anchimeric] nucleophilic assistance to solvolysis, and the chemical community continues to study the generation and reaction of these electrophiles . However, relatively little is known about the absolute barrier for addition of solvent to ring‐substituted phenonium ions.…”

Section: Methodsmentioning

confidence: 99%

“…[21,22] Bridging phenonium ions were at one time the subject of intense interest in studies to characterize internal [anchimeric] nucleophilic assistance to solvolysis, [23] and the chemical community continues to study the generation and reaction of these electrophiles. [24,25] However, relatively little is known about the absolute barrier for addition of solvent to ring-substituted phenonium ions. We are interested in designing experiments to examine these reaction barriers, so that they may be compared with barriers to nucleophile addition to related ringsubstituted 1-phenylethyl carbocations.…”

mentioning

confidence: 99%

Substituent effects on the formation and nucleophile selectivity of ring‐substituted phenonium ions in aqueous solution

Tsuji

Ogawa

Richard

2013

J of Physical Organic Chem

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The reaction of 2-(4-methyphenyl)ethyl tosylate (Me-1-OTs) in 50/50 (v/v) trifluoroethanol/water at 25 °C is first-order in the concentration of azide anion nucleophile. A carbon-13 NMR analysis of the products of the reactions of Me-1-[α–13C]OTs in 50/50 (v/v) trifluoroethanol/water at 25 °C shows the formation of Me-1-[β–13C]OH, Me-1-[β–13C]OCH2CF3 and Me-1-[β–13C]N3 from the trapping of a symmetrical 4-methylphenonium ion reaction intermediate Me-2+. The formation of Me-1-[α–13C]N3 by concerted bimolecular displacement of azide ion at Me-1-[α–13C]OTs (kN = 3.8 × 10−6 M−1 s−1) and of Me-1-[α–13C]OH and Me-1-[α–13C]OCH2CF3 by concerted bimolecular displacement of solvent (ksolv = 1.8 × 10−8 s−1) is also observed. An analysis of the rate and product data provides a value of kaz/ks = 32 M−1 for partitioning of Me-2+ between addition of azide ion and solvent that is nearly 3-fold smaller than kaz/ks = 83 M−1 reported in an earlier study on the partitioning of MeO-2+ [J. Org. Chem. 2011, 76, 9568]. This change is attributed to a decrease in nucleophile selectivity with increasing electrophile reactivity for the activation-limited addition of solvent and azide anion to X-2+. These data set a limit of 1/ks ≥ 10−7 s for the lifetime of Me-2+ in aqueous solution.

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“…The 4‐methoxyphenylium ion 8 + was generated by photolysis of 4‐chloroanisole in polar media and detected by flash photolysis (Scheme ). When this photochemical reaction is carried out in a polar solvent in the presence of dimethylbutene, a β‐alkoxyanisole product is isolated, which is thought to arise from trapping by trifluoroethanol of the sufficiently long‐lived 4‐methoxy substituted phenonium ion 9 + …”

Section: Lifetimes Of X‐4+mentioning

confidence: 99%

Formation and mechanism for reactions of ring‐substituted phenonium ions in aqueous solution

Tsuji

Richard

2015

J of Physical Organic Chem

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The results of studies on the structure and reactivity of spiro[5.2]oct-5,7-diene-4yl carbocation [phenonium ion] have had a significant impact on the course of discussion about the distinction between classical and nonclassical carbocations. This minireview will present a brief overview of the structure, bonding and reactivity of ring substituted phenonium ions (X-4+), with an emphasis on work completed since 2004. The discussion will focus on the development of new experimental protocol for determination of the selectivity for addition of nucleophilic anions to X-4+ in aqueous solution. The existing relationships between carbocation lifetime and nucleophilic selectivity, and the known lifetime of ca 140 sec for spiro[2.5]oct-4,7-diene-6-one provide rough estimates of the lifetimes for 4-Me-X-4+ and 4-MeO-X-4+ in aqueous solution. Evidence is presented that nucleophile addition to X-4+ proceeds through an “exploded” transition state, with relatively weak bonding the nucleophile and leaving group, and the development of significant positive charge at the reacting primary cyclopropyl carbon.

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Looking for a Paradigm for the Reactivity of Phenonium Ions

Cited by 25 publications

References 40 publications

Copper‐Catalyzed Direct Transformation of Secondary Allylic and Benzylic Alcohols into Azides and Amides: An Efficient Utility of Azide as a Nitrogen Source

Copper‐Catalyzed Direct Transformation of Secondary Allylic and Benzylic Alcohols into Azides and Amides: An Efficient Utility of Azide as a Nitrogen Source

Substituent effects on the formation and nucleophile selectivity of ring‐substituted phenonium ions in aqueous solution

Formation and mechanism for reactions of ring‐substituted phenonium ions in aqueous solution

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