<i>ipso</i> Nitration. XXVIII. Nitration of 4-substituted toluenes: 1,2 adducts

Fischer, Alfred; Fyles, Deborah L.; Henderson, George N.; Mahasay, Sumit Ray

doi:10.1139/v86-291

Cited by 9 publications

(4 citation statements)

References 18 publications

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“…The calculated product distribution for the nitration ofp-iodotoluene is similar to that for p-bromotoluene; however, little adduct is formed from p-iodotoluene. 2 Parallel observations have been made on the ortho-halogenotoluenes viz. 1,4-adducts are formed in significant yield from the fluoro, chloro, and bromo derivatives but not from the iodo c ~m p o u n d .…”

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confidence: 94%

Formation of aryliodine(III) derivatives in the nitration of aryl iodides in acetic anhydride

Bushnell¹,

Fischer²

1988

J. Chem. Soc., Perkin Trans. 2

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Nitration of iodobenzene, o-iodotoluene, and p-iodotoluene in acetic anhydride results in reversible oxidation to aryliodine( 111) compounds prior to the formation of the expected nitro derivatives. p-0x0-[nitrate( phenyl) iodine] [phenyl (trifluoroacetato) iodine] has been isolated from nitration of iodobenzene and its crystal structure determined.When 0-and p-iodo-toluene are nitrated in acetic anhydride the reactions do not go to completion under conditions which bring about complete reaction of the other halogenotoluenes and the iodotoluenes appear to be less reactive than the other halogenotoluenes. This is surprising since nitration of iodobenzene in aqueous sulphuric acid is faster than nitration of the other halogenobenzenes and additivity of substituent effects would suggest that this should also be true of the iodotoluenes. Nitration of p-fluoro-, p-chloro-, and p-bromotoluene in acetic anhydride gives good yields of adducts with nitro ips0 to methyl and lesser amounts of the nitro substitutionThe calculated product distribution for the nitration ofp-iodotoluene is similar to that for p-bromotoluene; however, little adduct is formed from p-iodotoluene.2 Parallel observations have been made on the ortho-halogenotoluenes viz. 1,4-adducts are formed in significant yield from the fluoro, chloro, and bromo derivatives but not from the iodo c~m p o u n d .~We have investigated the nitration of 0-and piodotoluene and of iodobenzene and have resolved these apparent anomalies. Results and DiscussionNitration Reactions.-0-lodotoluene. Nitration was carried out using a mixture of nitric acid, acetic anhydride, and trifluoroacetic anhydride and was followed by 'H n.m.r. spectroscopy. At -20 "C the o-iodotoluene reacted completely over a period of 30 min. The major component of the product mixture had 'H n.m.r. peaks similar to those of o-iodotoluene but shifted approximately 6 0.5 downfield. Some 2-iodo-4-nitroand 2-iodo-5-nitro-toluene were also formed and a minor amount ( c 10% of the product) of diene adduct. When the reaction mixture was worked-up after this time the major component of the isolated product mixture was o-iodotoluene and the major component in the reaction mixture was not present. When the reaction was carried out for an extended period (15 h) at low temperature, or for a shorter period (20 min) at ambient temperature, the first formed product disappeared and the iodonitrotoluenes were obtained. It is evident that the o-iodotoluene was initially converted reversibly into an intermediate from which the o-iodotoluene was regenerated as it was nitrated, or when the mixture was worked up. By analogy with the reaction of iodobenzene (below) this intermediate is assumed to be an o-iodosyltoluene derivative similar to (1). When the nitration was carried out in the absence of trifluoroacetic anhydride the reactions were similar although much slower, even at OOC, and the iodotoluene disappeared over 15 h. Again an intermediate was formed and nitration ensued.p-lodotoluene. Nitration was carried out with n...

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confidence: 94%

Formation of aryliodine(III) derivatives in the nitration of aryl iodides in acetic anhydride

Bushnell¹,

Fischer²

1988

J. Chem. Soc., Perkin Trans. 2

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“…There is no reason to believe that there are gross disparities in the degrees of ipso attack in acetic anhydride and aqueous sulphuric acid or aqueous acetic acid. The extent of nucleophilic capture on nitration of 2-methyl- (16,17), 4-methyl- (17,18), and 2-chloro-4-methyl-anisole (12,19) in acetic anhydride is comparable to that observed in nitrations in aqueous sulphuric acid. However, as the stability of the ipso nitrocyclohexadienyl cation is reduced, other reactions, such as rearrangement or the loss of nitronium ion, should start to compete with the trapping of the ipso cation.…”

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confidence: 66%

ipso Nitration in p-halophenyl ethers

Clewley¹,

Fischer²,

Henderson³

1989

Can. J. Chem.

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. Can. J. Chem. 67, 1472Chem. 67, (1989. Addition of nitronium ion ipso to halogen occurs on nitration of thep-haloanisoles in acetic anhydride at -60°C. In the cases of p-fluoro-andp-chloro-anisole, addition of the nitronium ion is reversible and only small amounts of ipso products are obtained. With p-bromoanisole nitrodebromination occurs. When p-halophenyl ethers containing a trapping substituent, e.g., 2-(4-chlorophenoxy)-2-methylpropanoic acid, are used as substrates, substantial amounts of the spiro diene with nitro ipso to halogen, e. g., 3,3-dimethyl-8-chloro-8-nitro-l,4-dioxaspiro[4.5]deca-6,9-dien-2-one, can be isolated. ' The results demonstrate that extensive ipso attack at the halogen-substituted position is general in the nitration ofp-halophenyl ethers.

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“…1981,103, 5190. common prejudice for wavelength-independent photochemistry (by analogy to Kasha's and Vavilov's rules for emission). 4 And in part, this question was not studied because suitable systems to reveal wavelength-dependent behavior were not readily available.…”

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Wavelength-dependent photochemistry of a diazo compound. Irradiation of 9-diazo-1,8-diazafluorene with ultraviolet or visible light

Li¹,

Schuster²

1987

J. Org. Chem.

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The photochemistry of 9-diazo-l,8-diazafluorene (18DAF) depends on the wavelength of the irradiating light. When photolyzed at ca. 310 nm, into a -* absorption band, excited 18DAF rearranges to a diazirine and loses nitrogen to form the carbene 1,8-diazafluorenylidene (18FL) exclusively in the singlet state. However, when 18DAF is photolyzed at ca. 420 nm, into the -* band, no diazirine is formed, but triplet 18FL is formed directly along (4) Turro, N.

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ipso Nitration. XXVIII. Nitration of 4-substituted toluenes: 1,2 adducts

Cited by 9 publications

References 18 publications

Formation of aryliodine(III) derivatives in the nitration of aryl iodides in acetic anhydride

Formation of aryliodine(III) derivatives in the nitration of aryl iodides in acetic anhydride

ipso Nitration in p-halophenyl ethers

Wavelength-dependent photochemistry of a diazo compound. Irradiation of 9-diazo-1,8-diazafluorene with ultraviolet or visible light

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