Ipso nitration. II. Novel products and true positional selectivities in nitration of p-cymene

Hahn, Roger C.; Strack, David L.

doi:10.1021/ja00820a054

Cited by 22 publications

(4 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With toluene ( 46 ), o -xylene ( 47 ), or anisole ( 48 ), para and ipso addition are predicted by spin densities in the radical cations. This may seem inconsistent with experiment; in fact, the ipso addition of electrophiles is well documented . Our results support the secondary rearrangement of initial ipso sigma complexes as a source of ortho products.…”

Section: Resultscontrasting

confidence: 74%

Beyond Frontier Molecular Orbital Theory: A Systematic Electron Transfer Model (ETM) for Polar Bimolecular Organic Reactions

Cahill

Johnson

2012

J. Org. Chem.

View full text Add to dashboard Cite

Polar bimolecular reactions often begin as charge-transfer complexes and may proceed with a high degree of electron transfer character. Frontier molecular orbital (FMO) theory is predicated in part on this concept. We have developed an electron transfer model (ETM) in which we systematically transfer one electron between reactants and then use density functional methods to model the resultant radical or radical ion intermediates. Sites of higher reactivity are revealed by a composite spin density map (SDM) of odd electron character on the electron density surface, assuming that a new two-electron bond would occur preferentially at these sites. ETM correctly predicts regio- and stereoselectivity for a broad array of reactions, including Diels-Alder, dipolar and ketene cycloadditions, Birch reduction, many types of nucleophilic additions, and electrophilic addition to aromatic rings and polyenes. Conformational analysis of radical ions is often necessary to predict reaction stereochemistry. The electronic and geometric changes due to one-electron oxidation or reduction parallel the reaction coordinate for electrophilic or nucleophilic addition, respectively. The effect is more dramatic for one-electron reduction.

show abstract

Section: Resultscontrasting

confidence: 74%

Beyond Frontier Molecular Orbital Theory: A Systematic Electron Transfer Model (ETM) for Polar Bimolecular Organic Reactions

Cahill

Johnson

2012

J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…In the final step, this activated proton is abstracted by a (weak) base, thus affording a C-substituted benzene derivative containing a new carbon−carbon bond. Alternatively, a nucleophile can add to the arenium ion, thus giving 1,2- or 1,4-disubstituted cyclohexadiene addition products (Scheme ) 1 …”

Section: Introductionmentioning

confidence: 99%

C_a_renium−C_a_lkylBond Making and Breaking: Key Process in the Platinum-Mediated C_a_ryl−C_a_lkylBond Formation. Analogies to Organic Electrophilic Aromatic Substitution

Albrecht

Spek

2001

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Abstract:The reaction of cationic platinum aqua complexes 2 [Pt(C 6 H 2 {CH 2 NMe 2 } 2 -E-4)(OH 2 )](X′) (X′ ) SO 3 CF 3 , BF 4 ) with alkyl halides RX gave various air-stable arenium complexes 3-5 containing a new C-C bond (R ) Me, 3; Et, 4; Bn, 5). Electron-releasing oxo-substituents on the aromatic ligand (E ) e.g., OH, b; OMe, c) enhance the reactivity of the aqua complex 2 and were essential for arenium formation from alkyl halides different from MeX. This process is initiated by oxidative addition of alkyl halides to the platinum(II) center of 2, which affords (alkyl)(aryl) platinum(IV) complexes (e.g., 9, alkyl ) benzyl) as intermediates. Spectroscopic analyses provided direct evidence for a subsequent reversible 1,2-sigmatropic shift of the alkyl group along the Pt-C aryl bond, which is identical to repetitive C arenium -C alkyl bond making and breaking and concerted metal reduction and oxidation. Temperature-dependent NMR spectroscopy revealed ∆H°) -1.3 (( 0.1) kJ mol -1 , ∆S°) +3.8 (( 0.2) J mol -1 K -1 , and ∆G°2 98 ) -2.4 (( 0.1) kJ mol -1 for the formation of the arenium complex 5b from 9 involving the migration of a benzyl group. The arenium complexes were transformed to cyclohexadiene-type addition products 7 or to demetalated alkyl-substituted arenes, 8, thus completing the platinum-mediated formation of a sp 2 -sp 3 C-C bond which is analogous to the aromatic substitution of a [PtX] + unit by an alkyl cation R + . The formation of related trimethylsilyl arenium complexes 6 suggests arenium complexes as key intermediates, not only in (metal-mediated) sp 2 -sp 3 C-C bond making and breaking but also in silyl-directed cyclometalation.

show abstract

“…The position il~so to the fert-butyl group is too hindered for attack of the nitronium ion to be competitive with attack at the other nuclear positions (15). i n contrast p-cymene does undergo attack ipso to the isopropyl group, both on reaction with nitric acid in acetic anhydride (6,16) and with nitronium tetrafluoroborate in tetramethylene s~llfone (15), and p-nitrotoluene is formed. N o side-chain (benzylic) products were obtained.…”

Section: Introductionmentioning

confidence: 99%

Nitration of p-tert-butyltoluene in acetic anhydride. 1,2 and 1,4 adducts

Fischer¹,

Röderer²

1976

Can. J. Chem.

View full text Add to dashboard Cite

Nitration of p-tert-butyltoluene in acetic anhydride gives 5-tert-butyl-2-methyl-2-nitro-1,2-dihydrophenyl acetate (43%), cis- and trans-1-tert-butyl-4-methyl-4-nitro-1,4-dihydrophenyl acetate (16%) and 4-tert-butyl-2-nitrotoluene (41%). Reaction of either of the 1,2 or 1,4 nitroacetoxy adducts with hydrogen chloride gives a mixture of the 1,2 and 1,4 nitrochloro adducts. The 1,2 (secondary) acetate adduct eliminates nitrous acid to form 5-tert-butyl-2-methylphenyl acetate under mildly acidic conditions. Under more vigorously acidic conditions 4-tert-butyl-2-nitrotoluene is formed. The same products are formed from the 1,4 (tertiary) acetate adducts but p-tolyl acetate is also obtained. The 1,2 and 1,4 adducts couple with anisole to form 5-tert-butyl-4′-methoxy-2-methylbiphenyl.

show abstract

Ipso nitration. II. Novel products and true positional selectivities in nitration of p-cymene

Cited by 22 publications

References 2 publications

Beyond Frontier Molecular Orbital Theory: A Systematic Electron Transfer Model (ETM) for Polar Bimolecular Organic Reactions

Beyond Frontier Molecular Orbital Theory: A Systematic Electron Transfer Model (ETM) for Polar Bimolecular Organic Reactions

C_a_renium−C_a_lkylBond Making and Breaking: Key Process in the Platinum-Mediated C_a_ryl−C_a_lkylBond Formation. Analogies to Organic Electrophilic Aromatic Substitution

Nitration of p-tert-butyltoluene in acetic anhydride. 1,2 and 1,4 adducts

Contact Info

Product

Resources

About

Ipso nitration. II. Novel products and true positional selectivities in nitration of p-cymene

Cited by 22 publications

References 2 publications

Beyond Frontier Molecular Orbital Theory: A Systematic Electron Transfer Model (ETM) for Polar Bimolecular Organic Reactions

Beyond Frontier Molecular Orbital Theory: A Systematic Electron Transfer Model (ETM) for Polar Bimolecular Organic Reactions

Carenium−CalkylBond Making and Breaking: Key Process in the Platinum-Mediated Caryl−CalkylBond Formation. Analogies to Organic Electrophilic Aromatic Substitution

Nitration of p-tert-butyltoluene in acetic anhydride. 1,2 and 1,4 adducts

Contact Info

Product

Resources

About

C_a_renium−C_a_lkylBond Making and Breaking: Key Process in the Platinum-Mediated C_a_ryl−C_a_lkylBond Formation. Analogies to Organic Electrophilic Aromatic Substitution